INTERNET DRAFT
NNTP                                                          C. Feather
  Expires: July 31, 2003
Internet-Draft                                                  Thus plc
                                                       January
Expires: August 30, 2003                                   March 1, 2003

                    Network News Transport Protocol
                   draft-ietf-nntpext-base-16.txt

  1
                       draft-ietf-nntpext-base-17

Status of this memo Memo

   This memo document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC 2026. RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as
   Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or made obsolete obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accesses accessed at
     http://www.ietf.org/ietf/1id-abstracts.txt. http://
   www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft shadow directories Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This section will be updated with the appropriate verbiage
     from RFC 2223 should this memo have been found ready for
     publication as an RFC. This update Internet-Draft will include its standards
     track status.

     This memo is a product of the NNTP Working Group, chaired by
     Russ Allbery.

  2 expire on August 30, 2003.

Copyright Notice

   Copyright (C) The Internet Society (2003).  All Rights Reserved.

Abstract

   The Network News Transport Protocol has been in use in the Internet
   for a decade and remains one of the most popular protocols (by
   volume) in use today.  This memo document is a replacement for RFC 977 and
   officially updates the protocol specification.  It clarifies some
   vagueness in RFC 977, includes some new base functionality and
   provides a specific mechanism to add standardized extensions to NNTP.

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  INTERNET DRAFT                                         C. Feather
  Expires: July 31, 2003                                   Thus plc
                                                       January 2003

  3   Introduction

Administration

   This memo specifies the Network News Transport Protocol
     (NNTP), which document is used for the distribution, inquiry,
     retrieval, and posting of net news articles using a reliable
     stream-based mechanism. For news reading clients, NNTP
     enables retrieval product of news articles that are stored in a
     central database, giving subscribers the ability to select
     only those articles they wish to read.

     The netnews model provides for indexing, cross-referencing,
     and expiration of aged messages. For server-to-server
     interaction, NNTP Working Group, chaired by Russ
   Allbery.

   This is designed for efficient transmission of
     net news articles over a reliable full duplex communication
     channel.

     Every attempt is made draft 17 pre-publication version 2.

Outstanding issues

   Outstanding substantive (as opposed to ensure that the protocol
     specification editorial) issues in this memo is compatible with the version
     specified text
   are shown as in RFC 977[1]. However, this version does not
     support the ill-defined SLAVE command and permits four digit
     years to following case.

   OUTSTANDING ISSUE

      Reference consistency: should every RFC that is mentioned be specified
      included in the NEWNEWS and NEWGROUPS commands.
     It changes references? Where the default character set same document is referred to UTF-8[2] instead of
     US-ASCII[3]. It also extends the newsgroup name matching
     capabilities already documented
      in RFC 977.

     Generally, new functionality is available using new keywords.
     Part of that new functionality involves more than one place, should every occasion have a mechanism to
     discover what new functionality reference
      number (that is, "RFC 977 [3]" or similar), or only the first one,
      or only the first one in each section?

Author's Note

   This draft is available to clients from the first produced using a server.

     This mechanism can also be used to add more functionality as
     needs merit such additions. new formatting process.  It
   therefore may contain unintentional layout or formatting changes
   compared with previous drafts.  The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
     NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
     "OPTIONAL" in author would appreciate being
   informed of any problems this memo are to be interpreted as described has caused.

   This draft is written in
     RFC 2119[4].

     An implementation XML using an NNTP-specific DTD.  Custom
   software is not compliant if it fails used to satisfy one
     or more of the MUST requirements for convert this protocol.  An
     implementation that satisfies all the MUST and all the SHOULD
     requirements for its protocols is said to be "unconditionally

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  INTERNET DRAFT                                         C. Feather
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                                                       January 2003

     compliant"; one that satisfies all the MUST requirements but
     not all RFC 2629 [12] format, and then
   the SHOULD requirements for NNTP is said public "xml2rfc" package to be
     "conditionally compliant".

     For the remainder of further reduce this memo, the term "client host" refers
     to a host making use of the NNTP service, while the term
     "server host" refers to a host that offers the NNTP service.
     In addition, where examples of interactions between a client
     host text, nroff
   source, and a server host are provided a "[C]" will be HTML.

   No perl was used to
     represent the client host and in producing this draft.

Rights

   UNIX is a "[S]" will be used to
     represent the server host.

     For the remainder registered trademark of this memo, responses will be described
     in tables listing the required format of a X/Open Company Ltd.

Table of Contents

   1.       Introduction . . . . . . . . . . . . . . . . . . . . . .   7
   2.       Notation . . . . . . . . . . . . . . . . . . . . . . . .   8
   3.       Basic Operation  . . . . . . . . . . . . . . . . . . . .   9
   3.1      Response Codes . . . . . . . . . . . . . . . . . . . . .  11
   3.1.1    Generic Response Codes . . . . . . . . . . . . . . . . .  13
   3.1.1.1  Examples . . . . . . . . . . . . . . . . . . . . . . . .  15
   3.2      Pipelining . . . . . . . . . . . . . . . . . . . . . . .  16
   3.2.1    Examples . . . . . . . . . . . . . . . . . . . . . . . .  17
   4.       The WILDMAT format . . . . . . . . . . . . . . . . . . .  18
   4.1      Wildmat syntax . . . . . . . . . . . . . . . . . . . . .  18
   4.2      Wildmat semantics  . . . . . . . . . . . . . . . . . . .  18
   4.3      Extensions . . . . . . . . . . . . . . . . . . . . . . .  19
   4.4      Examples . . . . . . . . . . . . . . . . . . . . . . . .  20
   5.       The GREETING Step  . . . . . . . . . . . . . . . . . . .  21
   5.1      Initial Connection . . . . . . . . . . . . . . . . . . .  21
   5.1.1    Usage  . . . . . . . . . . . . . . . . . . . . . . . . .  21
   5.1.2    Description  . . . . . . . . . . . . . . . . . . . . . .  21
   5.1.3    Examples . . . . . . . . . . . . . . . . . . . . . . . .  21
   5.2      MODE READER  . . . . . . . . . . . . . . . . . . . . . .  22
   5.2.1    Usage  . . . . . . . . . . . . . . . . . . . . . . . . .  22
   5.2.2    Description  . . . . . . . . . . . . . . . . . . . . . .  22
   5.2.3    Examples . . . . . . . . . . . . . . . . . . . . . . . .  23
   6.       The CAPABILITIES DISCOVERY step  . . . . . . . . . . . .  25
   6.1      LIST EXTENSIONS  . . . . . . . . . . . . . . . . . . . .  25
   6.1.1    Usage  . . . . . . . . . . . . . . . . . . . . . . . . .  25
   6.1.2    Description  . . . . . . . . . . . . . . . . . . . . . .  25
   6.1.3    Examples . . . . . . . . . . . . . . . . . . . . . . . .  26
   7.       Article posting and retrieval  . . . . . . . . . . . . .  27
   7.1      Group and article selection  . . . . . . . . . . . . . .  27
   7.1.1    GROUP  . . . . . . . . . . . . . . . . . . . . . . . . .  27
   7.1.1.1  Usage  . . . . . . . . . . . . . . . . . . . . . . . . .  28
   7.1.1.2  Description  . . . . . . . . . . . . . . . . . . . . . .  28
   7.1.1.3  Examples . . . . . . . . . . . . . . . . . . . . . . . .  29
   7.1.2    LAST . . . . . . . . . . . . . . . . . . . . . . . . . .  30
   7.1.2.1  Usage  . . . . . . . . . . . . . . . . . . . . . . . . .  30
   7.1.2.2  Description  . . . . . . . . . . . . . . . . . . . . . .  30
   7.1.2.3  Examples . . . . . . . . . . . . . . . . . . . . . . . .  31
   7.1.3    NEXT . . . . . . . . . . . . . . . . . . . . . . . . . .  32
   7.1.3.1  Usage  . . . . . . . . . . . . . . . . . . . . . . . . .  32
   7.1.3.2  Description  . . . . . . . . . . . . . . . . . . . . . .  32
   7.1.3.3  Examples . . . . . . . . . . . . . . . . . . . . . . . .  32
   7.2      Retrieval of articles and article sections . . . . . . .  33
   7.2.1    ARTICLE  . . . . . . . . . . . . . . . . . . . . . . . .  33
   7.2.1.1  Usage  . . . . . . . . . . . . . . . . . . . . . . . . .  33
   7.2.1.2  Description  . . . . . . . . . . . . . . . . . . . . . .  34
   7.2.1.3  Examples . . . . . . . . . . . . . . . . . . . . . . . .  35
   7.2.2    HEAD . . . . . . . . . . . . . . . . . . . . . . . . . .  36
   7.2.2.1  Usage  . . . . . . . . . . . . . . . . . . . . . . . . .  36
   7.2.2.2  Description  . . . . . . . . . . . . . . . . . . . . . .  37
   7.2.2.3  Examples . . . . . . . . . . . . . . . . . . . . . . . .  37
   7.2.3    BODY . . . . . . . . . . . . . . . . . . . . . . . . . .  39
   7.2.3.1  Usage  . . . . . . . . . . . . . . . . . . . . . . . . .  39
   7.2.3.2  Description  . . . . . . . . . . . . . . . . . . . . . .  39
   7.2.3.3  Examples . . . . . . . . . . . . . . . . . . . . . . . .  39
   7.2.4    STAT . . . . . . . . . . . . . . . . . . . . . . . . . .  40
   7.2.4.1  Usage  . . . . . . . . . . . . . . . . . . . . . . . . .  40
   7.2.4.2  Description  . . . . . . . . . . . . . . . . . . . . . .  41
   7.2.4.3  Examples . . . . . . . . . . . . . . . . . . . . . . . .  41
   7.3      Article posting  . . . . . . . . . . . . . . . . . . . .  42
   7.3.1    POST . . . . . . . . . . . . . . . . . . . . . . . . . .  42
   7.3.1.1  Usage  . . . . . . . . . . . . . . . . . . . . . . . . .  42
   7.3.1.2  Description  . . . . . . . . . . . . . . . . . . . . . .  43
   7.3.1.3  Examples . . . . . . . . . . . . . . . . . . . . . . . .  44
   7.3.2    IHAVE  . . . . . . . . . . . . . . . . . . . . . . . . .  44
   7.3.2.1  Usage  . . . . . . . . . . . . . . . . . . . . . . . . .  44
   7.3.2.2  Description  . . . . . . . . . . . . . . . . . . . . . .  45
   7.3.2.3  Examples . . . . . . . . . . . . . . . . . . . . . . . .  46
   8.       Information commands . . . . . . . . . . . . . . . . . .  48
   8.1      DATE . . . . . . . . . . . . . . . . . . . . . . . . . .  48
   8.1.1    Usage  . . . . . . . . . . . . . . . . . . . . . . . . .  48
   8.1.2    Description  . . . . . . . . . . . . . . . . . . . . . .  48
   8.1.3    Examples . . . . . . . . . . . . . . . . . . . . . . . .  48
   8.2      HELP . . . . . . . . . . . . . . . . . . . . . . . . . .  48
   8.2.1    Usage  . . . . . . . . . . . . . . . . . . . . . . . . .  48
   8.2.2    Description  . . . . . . . . . . . . . . . . . . . . . .  49
   8.2.3    Examples . . . . . . . . . . . . . . . . . . . . . . . .  49
   8.3      NEWGROUPS  . . . . . . . . . . . . . . . . . . . . . . .  49
   8.3.1    Usage  . . . . . . . . . . . . . . . . . . . . . . . . .  49
   8.3.2    Description  . . . . . . . . . . . . . . . . . . . . . .  49
   8.3.3    Examples . . . . . . . . . . . . . . . . . . . . . . . .  50
   8.4      NEWNEWS  . . . . . . . . . . . . . . . . . . . . . . . .  50
   8.4.1    Usage  . . . . . . . . . . . . . . . . . . . . . . . . .  51
   8.4.2    Description  . . . . . . . . . . . . . . . . . . . . . .  51
   8.4.3    Examples . . . . . . . . . . . . . . . . . . . . . . . .  51
   8.5      Time . . . . . . . . . . . . . . . . . . . . . . . . . .  52
   8.5.1    Examples . . . . . . . . . . . . . . . . . . . . . . . .  52
   8.6      The LIST commands  . . . . . . . . . . . . . . . . . . .  53
   8.6.1    LIST ACTIVE  . . . . . . . . . . . . . . . . . . . . . .  53
   8.6.1.1  Usage  . . . . . . . . . . . . . . . . . . . . . . . . .  53
   8.6.1.2  Description  . . . . . . . . . . . . . . . . . . . . . .  53
   8.6.1.3  Examples . . . . . . . . . . . . . . . . . . . . . . . .  54
   8.6.2    LIST ACTIVE.TIMES  . . . . . . . . . . . . . . . . . . .  55
   8.6.2.1  Usage  . . . . . . . . . . . . . . . . . . . . . . . . .  55
   8.6.2.2  Description  . . . . . . . . . . . . . . . . . . . . . .  55
   8.6.2.3  Examples . . . . . . . . . . . . . . . . . . . . . . . .  55
   8.6.3    LIST DISTRIBUTIONS . . . . . . . . . . . . . . . . . . .  56
   8.6.3.1  Usage  . . . . . . . . . . . . . . . . . . . . . . . . .  56
   8.6.3.2  Description  . . . . . . . . . . . . . . . . . . . . . .  56
   8.6.3.3  Examples . . . . . . . . . . . . . . . . . . . . . . . .  57
   8.6.4    LIST DISTRIB.PATS  . . . . . . . . . . . . . . . . . . .  57
   8.6.4.1  Usage  . . . . . . . . . . . . . . . . . . . . . . . . .  57
   8.6.4.2  Description  . . . . . . . . . . . . . . . . . . . . . .  57
   8.6.4.3  Examples . . . . . . . . . . . . . . . . . . . . . . . .  58
   8.6.5    LIST NEWSGROUPS  . . . . . . . . . . . . . . . . . . . .  58
   8.6.5.1  Usage  . . . . . . . . . . . . . . . . . . . . . . . . .  58
   8.6.5.2  Description  . . . . . . . . . . . . . . . . . . . . . .  59
   8.6.5.3  Examples . . . . . . . . . . . . . . . . . . . . . . . .  59
   9.       The CONCLUSION step  . . . . . . . . . . . . . . . . . .  60
   9.1      QUIT . . . . . . . . . . . . . . . . . . . . . . . . . .  60
   9.1.1    Usage  . . . . . . . . . . . . . . . . . . . . . . . . .  60
   9.1.2    Description  . . . . . . . . . . . . . . . . . . . . . .  60
   9.1.3    Examples . . . . . . . . . . . . . . . . . . . . . . . .  60
   10.      Framework for NNTP extensions  . . . . . . . . . . . . .  61
   10.1     Initial IANA registry  . . . . . . . . . . . . . . . . .  63
   10.2     Standard extensions  . . . . . . . . . . . . . . . . . .  63
   10.3     The LISTGROUP extension  . . . . . . . . . . . . . . . .  63
   10.3.1   LISTGROUP  . . . . . . . . . . . . . . . . . . . . . . .  63
   10.3.1.1 Usage  . . . . . . . . . . . . . . . . . . . . . . . . .  63
   10.3.1.2 Description  . . . . . . . . . . . . . . . . . . . . . .  64
   10.3.1.3 Examples . . . . . . . . . . . . . . . . . . . . . . . .  64
   10.4     Article metadata . . . . . . . . . . . . . . . . . . . .  65
   10.4.1   The :bytes metadata item . . . . . . . . . . . . . . . .  65
   10.4.2   The :lines metadata item . . . . . . . . . . . . . . . .  66
   10.5     The OVER extension . . . . . . . . . . . . . . . . . . .  66
   10.5.1   OVER . . . . . . . . . . . . . . . . . . . . . . . . . .  66
   10.5.1.1 Usage  . . . . . . . . . . . . . . . . . . . . . . . . .  66
   10.5.1.2 Description  . . . . . . . . . . . . . . . . . . . . . .  67
   10.5.1.3 Examples . . . . . . . . . . . . . . . . . . . . . . . .  68
   10.5.2   LIST OVERVIEW.FMT  . . . . . . . . . . . . . . . . . . .  69
   10.5.2.1 Usage  . . . . . . . . . . . . . . . . . . . . . . . . .  69
   10.5.2.2 Description  . . . . . . . . . . . . . . . . . . . . . .  70
   10.5.2.3 Examples . . . . . . . . . . . . . . . . . . . . . . . .  71
   10.6     The HDR extension  . . . . . . . . . . . . . . . . . . .  72
   10.6.1   HDR  . . . . . . . . . . . . . . . . . . . . . . . . . .  72
   10.6.1.1 Usage  . . . . . . . . . . . . . . . . . . . . . . . . .  72
   10.6.1.2 Description  . . . . . . . . . . . . . . . . . . . . . .  72
   10.6.1.3 Examples . . . . . . . . . . . . . . . . . . . . . . . .  74
   11.      Augmented BNF Syntax for NNTP Commands . . . . . . . . .  76
   12.      Security Considerations  . . . . . . . . . . . . . . . .  79
   12.1     Personal and Proprietary Information . . . . . . . . . .  79
   12.2     Abuse of Server Log Information  . . . . . . . . . . . .  79
   12.3     Weak Authentication and Access Control . . . . . . . . .  79
   12.4     DNS Spoofing . . . . . . . . . . . . . . . . . . . . . .  80
   12.5     UTF-8 issues . . . . . . . . . . . . . . . . . . . . . .  80
   13.      Acknowledgments  . . . . . . . . . . . . . . . . . . . .  82
            Normative References . . . . . . . . . . . . . . . . . .  84
            Informative References . . . . . . . . . . . . . . . . .  85
            Author's Address . . . . . . . . . . . . . . . . . . . .  85
            Intellectual Property and Copyright Statements . . . . .  86

1. Introduction

   This document specifies the Network News Transport Protocol (NNTP),
   which is used for the distribution, inquiry, retrieval, and posting
   of net news articles using a reliable stream-based mechanism.  For
   news reading clients, NNTP enables retrieval of news articles that
   are stored in a central database, giving subscribers the ability to
   select only those articles they wish to read.

   The net news model provides for indexing, cross-referencing, and
   expiration of aged messages.  For server-to-server interaction, NNTP
   is designed for efficient transmission of net news articles over a
   reliable full duplex communication channel.

   Every attempt is made to ensure that the protocol specification in
   this document is compatible with the version specified in RFC 977
   [1].  However, this version does not support the ill-defined SLAVE
   command and permits four digit years to be specified in the NEWNEWS
   and NEWGROUPS commands.  It changes the default character set to
   UTF-8 [2] instead of US-ASCII [3].  It also extends the newsgroup
   name matching capabilities already documented in RFC 977.

   Generally, new functionality is made available using new commands.
   Part of that new functionality involves a mechanism to discover what
   new functionality is available to clients from a server.

   This mechanism can also be used to add more functionality as needs
   merit such additions.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [4].

   An implementation is not compliant if it fails to satisfy one or more
   of the MUST requirements for this protocol.  An implementation that
   satisfies all the MUST and all the SHOULD requirements for its
   protocols is said to be "unconditionally compliant"; one that
   satisfies all the MUST requirements but not all the SHOULD
   requirements for NNTP is said to be "conditionally compliant".

   For the remainder of this document, the term "client host" refers to
   a host making use of the NNTP service, while the term "server host"
   refers to a host that offers the NNTP service.

2. Notation

   The following notational conventions are used in this document.

     UPPERCASE     indicates literal text to be included in the
                   command;
     lowercase     indicates a token described elsewhere;
     [brackets]    indicate that the parameter is optional;
     ellipsis...   indicates that the parameter may be repeated any
                   number of times (it must occur at least once);
     vertical|bar  indicates a choice of two mutually exclusive
                   parameters (exactly one must be provided).

   The name "message-id" for a command or response parameter indicates
   that it is the message-id of an article as described in Section 7.
   The actual parameter MUST include the angle brackets.

   The name "wildmat" for a parameter indicates that it is a wildmat as
   defined in Section 4.  If the parameter does not meet the
   requirements of that section (for example, if it does not fit the
   grammar of Section 4.1) the NNTP server MAY place some interpretation
   on it (not specified by this document) or otherwise MUST treat it as
   a syntax error.

   Responses for each command will be described in tables listing the
   required format of a response followed by the meaning that should be
   ascribed to that response.

  4

   Examples in this document are not normative but serve to illustrate
   usages, arguments, and responses.  In the examples, a "[C]" will be
   used to represent the client host and a "[S]" will be used to
   represent the server host.  Most of the examples do not rely on a
   particular server state.  In some cases, however, they do assume that
   the current selected newsgroup (see the GROUP command (Section
   7.1.1)) is invalid; when so, this is indicated at the start of the
   example.

3. Basic Operation. Operation

   Every NNTP session MUST involve the following in this order:

      CONNECTION
      GREETING
      DISCONNECTION

   Other steps may occur between the GREETING and DISCONNECTION step.
   They are:

      CAPABILITIES DISCOVERY
      NEWS EXCHANGE
      CONCLUSION

   NNTP operates over any reliable data stream 8-bit-wide channel.  When
   running over TCP/IP, the official port for the NNTP service is 119.
   Initially, the server host starts the NNTP service by listening on a
   TCP port.  When a client host wishes to make use of the service, it
   MUST establish a TCP connection with the server host by connecting to
   that host on the same port on which the server is listening.  This is
   the CONNECTION step.  When the connection is established, the NNTP
   server host MUST send a greeting.  This is the GREETING step.  The
   client host and server host SHOULD then exchange commands and
   responses (respectively) until the connection is closed or aborted.
   This final step is called the DISCONNECTION step.

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   If there is a CONCLUSION step, it MUST immediately precede the
   DISCONNECTION step.  There MUST be only one CONNECTION, CONCLUSION
   and DISCONNECTION step for each NNTP session.  All other steps MAY be
   repeated as needed.  For example, the GREETING step may be repeated
   if the client makes use of the MODE READER command (See (see Section 7.2 5.2
   for more on the MODE READER command).

   OUTSTANDING ISSUE

      Do we actually need this GREETING / NEWS EXCHANGE / DISCONNECTION
      type stuff? I don't see that it buys us anything compared with
      simply saying that there's the initial greeting and a set of
      commands.

   The character set for all NNTP commands is UTF-8.  Commands in the
   NNTP MUST consist of an US-ASCII case-insensitive a keyword, which MAY be followed by one or more
   arguments.  An US-ASCII CRLF pair MUST terminate all commands.
   Multiple commands MUST NOT be on the same line.  Keywords MUST
   consist of printable US-ASCII characters.  Unless otherwise noted
   elsewhere in this memo, document, arguments SHOULD consist of printable
   US-ASCII characters.  Keywords and arguments MUST be each separated
   by one or more US-ASCII SPACE or US-ASCII TAB characters.  Keywords
   MUST be at least three US-ASCII characters and MUST NOT exceed 12
   US-ASCII characters.  Command lines MUST NOT exceed 512 octets, which
   includes the terminating US-ASCII CRLF pair. Arguments  The arguments MUST NOT
   exceed 497 octets.

   Commands may have variants, using a second keyword immediately after
   the first to indicate which variant is required.  The only such
   commands in this specification are LIST and MODE.

   Keywords are case-insensitive; the case of keywords for commands MUST
   be ignored by the server.  Command and response parameters are case
   or language specific only when specified (either in this document or
   in RFC 1036 [6]).

   An NNTP server MUST implement all the commands in this specification
   except for those marked as optional and those in extensions.

   Each response MUST start with a three-digit response code that is
   sufficient to distinguish all responses.  Certain valid responses are
   defined to be multi-line; for all others, the response is contained
   in a single line.

   OUTSTANDING ISSUE

      Should the initial response line be limited to 512 octets as well?
      Possible text:

      The first or only line of the response MUST NOT exceed 512 octets,
      which includes the response code and the terminating US-ASCII CRLF
      pair.

      The text further down about "does not place any limit on the
      length" would need equivalent edits.

   All multi-line responses MUST adhere to the following format:

   1.  The response consists of a sequence of one or more "lines", each
       being a stream of octets ending with 0x0D 0x0A (US-ASCII CRLF).
       Apart from those line endings, the stream MUST NOT include the
       octets 0x00, 0x0A, or 0x0D (US-ASCII NUL, LF, and CR).

   2.  The first such line contains the response code as with a single
       line response.

   3.  If any subsequent line begins with the "termination octet" (0x2E
       or US_ASCII "."), that line MUST be "byte-stuffed" by

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       an additional termination octet (0x2E) to that line of the
       response.

   4.  The lines of the response MUST be followed by a terminating line
       consisting of a single termination octet (0x2E or US_ASCII ".")followed ".")
       followed by CRLF in the normal way.  Thus a multi-line response
       is always terminated with the five octets
     "CRLF.CRLF" CRLF "." CRLF (in
       US-ASCII).

     There is NO limit on the length of a line.

   5.  When interpreting a multi-line response, the "byte stuffing" MUST
       be undone; i.e.  the client MUST ensure that, in any line
       beginning with the termination octet followed by octets other
       than US-ASCII CRLF, that initial termination octet is
       disregarded.

   6.  Likewise, the terminating line ".CRLF" "." CRLF (in US-ASCII) MUST NOT be
       considered part of the multi-line response; i.e.  the client MUST
       ensure that any line beginning with the termination octet
       followed immediately by US-ASCII CRLF is disregarded; (the first
       CRLF of the terminating "CRLF.CRLF" CRLF "." CRLF is, of course, part of the
       last line of the response).

     NOTE: Texts

   Note that texts using an encoding (such as UTF-16 or UTF-32) that may
   contain the NUL octet or the CR or LF octets in contexts other than
   the CRLF line ending cannot be reliably conveyed in the above format.

     Note also that, although this memo

   This document does not place any limit on the length of a line in any way, line.
   However, the standards that define the format of articles may do so.

   An NNTP server MAY have an inactivity autologout timer.  Such a timer
   SHOULD be of at least three minutes duration, with the exception that
   there MAY be a shorter limit on how long the server is willing to
   wait for the first command from the client.  The receipt of any
   command from the client during the timer interval SHOULD suffice to
   reset the autologout timer.  Similarly, the receipt of any
   significant amount of data from the client while in the midst of
   sending a multi-
     line multi-line message to the server (such as during a POST or
   IHAVE

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                                                       January 2003 command) SHOULD suffice to reset the autologout timer.  When
   the timer expires, the server SHOULD close the TCP connection without
   sending any response to the client, including when the client is in
   the middle of sending a multi-line message to the server.

  4.1

3.1 Response Codes

   Each response MUST begin with a three-digit status indicator.  These
   are status reports from the server and indicate the response to the
   last command received from the client.

   The first digit of the response broadly indicates the success,
   failure, or progress of the previous command.

      1xx - Informative message message.
      2xx - Command ok completed OK.
      3xx - Command ok OK so far, far; send the rest of it.
      4xx - Command was correct, but couldn't be performed for some
      reason.
      5xx - Command unimplemented, or incorrect, or a serious program
      error occurred.

   The next digit in the code indicates the function response category.

      x0x - Connection, setup, and miscellaneous messages
      x1x - Newsgroup selection
      x2x - Article selection
      x3x - Distribution functions
      x4x - Posting
      x8x - Reserved for authentication and authorization extensions
      x9x - Reserved for private use (non-standard extensions)

   Certain responses contain parameters such as numbers and names in
   addition to the status indicator.  In those cases, to simplify
   interpretation by the client the number and type of such parameters
   is fixed for each response code to simplify interpretation by code, as is whether or not the client (any code
   introduces a multi-line response.  Any extension MUST follow this
   principle as well). well, but note that, for historical reasons, the 211
   response code is an exception to this.  In all other cases, the
   client MUST only use the status indicator itself to determine the
   nature of the response.  The exact response

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   returned in response to a by any given command are detailed in the description of the keyword that is the first
     part of the
   command.

   Parameters MUST be separated from the numeric status indicator and
   from each other by a single US-ASCII space.  All numeric parameters
   MUST be in base 10 (decimal) format, and MAY have leading zeros.
   String parameters MUST contain at least one character and MUST NOT
   contain US-ASCII spaces, CR, LF, or tab). tab.  The server MAY add any text after the text
   after the response code or last parameter as appropriate, and the
   client MUST NOT make decisions based on this text.  Such text MUST be
   separated from the numeric status indicator or the last parameter by
   at least one US-ASCII space.

   The server MUST respond to any command with the appropriate generic
   response (given in Section 3.1.1) if it represents the situation.
   Otherwise, each recognized command MUST return one of the response
   codes specifically listed in its description or in an extension.  A
   server MAY provide extensions to this specification, including new
   commands, new variants or features of existing commands, and other
   ways of changing the internal state of the server.  However, the
   server MUST NOT produce any other responses to a client that does not
   invoke any of the additional features.  (Therefore a client that
   restricts itself to this specification will only receive the
   responses that are listed.)

   If a client receives an unexpected response, it SHOULD use the first
   digit of the response to determine the result.  For example, an
   unexpected 2xx should be taken as success and an unexpected 4xx or
   5xx as failure.

   Response codes not specified in this document MAY be used for any
   installation-specific additional commands also not specified.  These
   SHOULD be chosen to fit the pattern of x9x specified above.

   Neither this document nor any extension registered with IANA (see
   Section 10) will specify any response
     code or last parameter as appropriate, and codes of the client MUST
     NOT make decisions based on this text. Such text MUST x9x pattern.
   (Implementers of extensions are accordingly cautioned not to use such
   responses for extensions that may subsequently be
     separated from the numeric status indicator or the last
     parameter by at least one US-ASCII space. submitted for
   registration.)

3.1.1 Generic Response Codes

   The server MUST respond to any command with the appropriate one of
   the following generic response (given in section 4.1.1) responses if it represents the situation. Otherwise, each recognized

   If the command is not recognized, or it is an optional command or
   extension that is not implemented by the server, the response code
   500 MUST return
     one be returned.

   If there is a syntax error in the arguments of a recognized command,
   including the case where more arguments are provided than the command
   specifies, the response codes specifically listed code 501 MUST be returned.  Note that where a
   command has variants depending on a second keyword (e.g.  LIST ACTIVE
   and LIST NEWSGROUPS), then 501 MUST be used when the requested
   variant is not implemented but the base command is.

   If the client is not authorized to use the specified facility when
   the server is in its
     description or in an extension. current state, the response code 502 MUST be
   returned.  A different command might change the server MAY state and
   permit the command if it is retried.

   If the server does not provide
     extensions to this memo, including new commands, new features
     of existing commands, an optional feature, then the response
   code 403 MUST be returned if the omission is temporary (e.g.  because
   a necessary facility is unavailable) and other ways of changing the internal
     state of the server. However, code 503 if it is
   permanent (e.g.  because the server MUST NOT produce any
     other responses to a client that does not invoke any of store the
     additional features. (Therefore required
   information).

   OUTSTANDING ISSUE

      Is anyone aware of a client server that restricts
     itself implements 403, or is it an
      invention of our own? If the latter, do we want to this memo will only receive keep it? INN
      apparently uses 503 for temporary errors; someone suggested adding
      the responses that are
     listed). text:

         If a client receives the server encounters an unexpected response, internal error that
         prevents it SHOULD use
     the first digit of from completing a command, the response to determine the result. For
     example, an unexpected 2xx should be taken as success and an
     unexpected 4xx or 5xx as failure.

     Response codes not specified in this memo code 503
         MAY be used returned.

      Some servers return 503 for any
     installation-specific additional commands also not specified.
     These SHOULD be chosen to fit the pattern of x9x specified
     above.

     Neither this memo nor any extension registered with IANA (see
     section 12) will specify any things like "can't contact a posting
      server" or "can't execute external authenticator".

   OUTSTANDING ISSUE

      The 503 response codes of the x9x
     pattern. (Implementers of extensions are accordingly

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     cautioned not seems to have three separate meanings:

      1.  LIST ACTIVE.TIMES etc.  use such responses it for extensions that may
     subsequently be submitted "this data isn't stored".
          HDR uses it for registration.)

  4.1.1  Generic Response Codes

     The server MUST respond to any command with the appropriate
     one "this header can't be requested", which is
          consistent.  Are there other commands that can reasonably
          return such a thing? If not, is this kind of the following 503 really a
          generic responses if it represents the
     situation.

     If response?

      2.  Temporary errors, the command kind that 403 is not recognized, or supposed to represent.

      3.  It's apparently returned by LIST EXTENSIONS, but what does it is
          mean in this case? Not "there are no extensions", because
          that's 402.  Is this also an optional
     command or extension that is not implemented by the server,
     the response invention of our own? Again,
          would a different code 500 MUST be returned. better?

   If there is a syntax error in the arguments of a recognized
     command, server has to terminate the response code 501 connection for some reason, it
   MUST be returned. Note that
     where give a 400 response code to the next command has variants depending on a keyword (e.g.
     LIST ACTIVE and LIST NEWSGROUPS), then 501 MUST be used when
   immediately close the requested variant TCP connection.  It MAY give a 401 response
   code to any command to indicate that termination is not implemented but imminent
   (following a 401 response, it MUST NOT close the base command
     is.

     If TCP connection
   immediately).

   OUTSTANDING ISSUE

      Since the client is not authorized to use 401 doesn't terminate the specified facility
     when session, what about commands
      that change the status? For example, if GROUP returns 401 what
      happens to the server is in its current state, selected newsgroup.

   With the response code
     502 exception of mandatory commands and the 500 response, the
   client MUST be returned. A different prepared to receive any of these responses for any
   command.

3.1.1.1 Examples

   Example of an unknown command:

      [C] MAIL
      [S] 500 Unknown command might change the
     server state and permit the

   Example of an unsupported extension:

      [C] LIST EXTENSIONS
      [S] 202 Extensions supported:
      [S] LISTGROUP
      [S] .
      [C] OVER
      [S] 500 Unknown command if it is retried.

     If the server does not provide

   Example of an unsupported variant:

      [C] MODE POSTER
      [S] 501 Unknown MODE option

   Example of a syntax error:

      [C] ARTICLE a.message.id@no.angle.brackets
      [S] 501 Syntax error

   Example of an overlong command line:

      [C] HEAD 53 54 55
      [S] 501 Too many arguments

   Example of a bad wildmat:

      [C] LIST ACTIVE u[ks].*
      [S] 501 Syntax error

   Example of an optional feature, then the
     response code 403 MUST be returned if the omission is
     temporary (e.g. because attempt to access a necessary facility is unavailable)
     and the code 503 if it is permanent  (e.g. because the restricted facility:

      [C] GROUP secret.group
      [S] 502 Permission denied

   followed by a successful attempt following authentication:

      [C] XSECRET fred flintstone
      [S] 290 Password for fred accepted.
      [C] GROUP secret.group
      [S] 211 5 1 20 secret.group selected
   Example of a temporary failure:

      [C] GROUP archive.local
      [S] 403 Archive server
     does not store the required information).

     If temporarily offline

   Example of the server has to terminate the connection for some
     reason, it MUST give a 400 response code needing to the next command
     and then immediately close the TCP connection. It MAY give a
     401 response code to any command to indicate that termination
     is down immediately:

      [C] ARTICLE 123
      [S] 400 Power supply failed, running on UPS
      [Server closes connection.]

   Example of imminent (following a 401 response, it MUST NOT close termination of the
     TCP connection immediately).

  4.2  Streaming server:

      [C] STAT 123
      [S] 401 Pre-payment expired, you have 10 seconds
      [C] STAT 123
      [S] 423 No such article number in this group
      [C] NEXT
      [S] 400 Time expired
      [Server closes connection.]

3.2 Pipelining

   NNTP is designed to operate over a reliable bi-directional connection
   such as TCP.  Therefore, if a command does not

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   to the previous one, it should not matter if it is sent before that
   response is received.  Doing this is called "streaming". "pipelining".  However,
   certain server implementations throw away all text received from the
   client following certain commands before sending their response.  If
   this happens, streaming pipelining will be affected because one or more
   commands will have been ignored or misinterpreted, and the client
   will be matching the wrong responses to each command.  Since there
   are significant benefits to streaming, pipelining, but also circumstances where
   it is reasonable or common for servers to behave in the above manner,
   this memo document puts certain requirements on both clients and servers.

   Except where stated otherwise, a client MAY use streaming. pipelining.  That is,
   it may send a command before receiving the response for the previous
   command.  The server MUST allow streaming pipelining and MUST NOT throw away
   any text received after a command.
     Finally,  Irrespective of whether or not
   pipelining is used, the server MUST process commands in the order
   they are sent.

   If the specific description of a command describes say it as "not
     streamable", "MUST NOT be
   pipelined", that command MUST end any stream pipeline of commands.  That is,
   the client MUST NOT send any following command until receiving the
   CRLF at the end of the response from the command.  The server MAY
   ignore any data received after the command and before the CRLF at the
   end of the response is sent to the client.

   The initial connection must not be part of a stream; pipeline; that is, the
   client MUST NOT send any command until receiving the CRLF at the end
   of the greeting.

   If the client uses blocking system calls to send commands, it MUST
   ensure that the amount of text sent in streaming pipelining does not cause a
   deadlock between transmission and reception.  The
     amount of text involved will depend on window sizes in amount of text
   involved will depend on window sizes in the transmission layer, and
   is typically 4k octets for TCP.

3.2.1 Examples

   Example of correct use of pipelining:

      [C] GROUP misc.test
      [C] STAT
      [C] NEXT
      [S] 211 1234 3000234 3002322 misc.test
      [S] 223 3000234 <45223423@example.com> retrieved
      [S] 223 3000237 <668929@example.org> retrieved

   Example of incorrect use of pipelining (the LIST EXTENSIONS command
   may not be pipelined):

      [C] GROUP misc.test
      [C] LIST EXTENSIONS
      [C] DATE
      [C] NEXT
      [S] 211 1234 3000234 3002322 misc.test
      [S] 402 server has no extensions
      [S] 223 3000237 <668929@example.org> retrieved

   The DATE command has been thrown away by the
     transmission layer, server and so there is typically 4k bytes for TCP.

  5
   no 111 response to match it.

4. The WILDMAT format

   The WILDMAT format described here is based on the version first
   developed by Rich Salz [5], [11], which in turn was derived

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   format used in the UNIX "find" command to articulate file names.  It
   was developed to provide a uniform mechanism for matching newsgroup names patterns in
   the same manner that the UNIX shell matches filenames.

  5.1

4.1 Wildmat syntax

   A wildmat is described by the following augmented BNF[6] BNF [5] syntax
   (note that this syntax contains ambiguities and special cases
   described at the end):

      wildmat = wildmat-pattern *("," ["!"] wildmat-pattern)

      wildmat-pattern = 1*wildmat-item

      wildmat-item = wildmat-exact / wildmat-wild

      wildmat-exact = %x21-29 / %x2B / %x2D-3E / %x40-5A / %x5E-
              7F /UTF-8-non-ascii %x5E-7E /
         UTF-8-non-ascii ; exclude * , ? [ \ ]

      wildmat-wild = "*" / "?"

   UTF-8-non-ascii is defined in section 13. Section 11

   This syntax must be interpreted subject to the following rule:

   Where a wildmat-pattern is not immediately preceded by "!", it shall
   not begin with a "!".

     NOTE:

   Note: the characters \ , [ and ] are not allowed in wildmats, while *
   and ? are always wildcards.  This should not be a problem since these
   characters cannot occur in newsgroup names, which is the only current
   use of wildmats.  Backslash is commonly used to supress the special
   meaning of characters and brackets to introduce sets, but there is no
   existing standard practice for these in wildmats and so they were
   omitted from this memo. specification.  A future extension to this memo
   specification may provide semantics for these characters.

  5.2

4.2 Wildmat semantics

   A wildmat is tested against a string, and either matches or does not
   match.  To do this, each constituent wildmat-pattern

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   against the string and the rightmost pattern that matches is
   identified.  If that wildmat-pattern is not preceded with "!", the
   whole wildmat matches.  If it is preceded by "!", or if no
   wildmat-pattern matches, the whole wildmat does not match.

   For example, consider the wildmat "a*,!*b,*c*":

      the string "aaa" matches because the rightmost match is with "a*"

      the string "abb" does not match because the rightmost match is
      with "*b"

      the string "ccb" matches because the rightmost match is with "*c*"

      the string "xxx" does not match because no wildmat-pattern matches

   A wildmat-pattern matches a string if the string can be broken into
   components, each of which matches the corresponding wildmat-item in
   the pattern; the matches must be in the same order, and the whole
   string must be used in the match.  The pattern is "anchored"; that
   is, the first and last characters in the string must match the first
   and last item respectively (unless that item is an asterisk matching
   zero characters).

   A wildmat-exact matches the same character (which may be more than
   one octet in UTF-8).

   "?" matches exactly one character (which may be more than one octet).

   "*" matches zero or more characters.  It can match an empty string,
   but it cannot match a subsequence of a UTF-8 sequence that is not
   aligned to the character boundaries.

  5.3

4.3 Extensions

   An NNTP server or extension MAY extend the syntax or semantics of
   wildmats provided that all wildmats that meet the requirements of section 5.1
   Section 4.1 have the meaning ascribed to

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                                                       January 2003 them by section 5.2. Section 4.2.  Future
   editions of this memo document may also extend wildmats.

  5.4

4.4 Examples

    In these examples, $ and @ are used to represent the two octets 0xC2
   and 0xA3 respectively; $@ is thus the UTF-8 encoding for the pound
   sterling symbol, shown as # in the descriptions.

     Wildmat    Description of strings that match
       abc      the one string "abc"
       abc,def  the two strings "abc" and "def"
       $@       the one character string "#"
       a*       any string that begins with "a"
       a*b      any string that begins with "a" and ends with "b"
       a*,*b    any string that begins with "a" or ends with "b"
       a*,!*b   any string that begins with "a" and does not end with
                "b"
     a*,!*b,c*  any string that begins with "a" and does not end with
     a*,!*b,c*
                "b", and any string that begins with "c" no matter
                what it ends with
                any string that begins with "a" or "c" and does ends with
     a*,c*,!*b  any string that begins with "a" or "c" and does not
                end with "b"
       ?a*      any string with "a" as its second character
       ??a*     any string with "a" as its third character
       *a?      any string with "a" as its penultimate character
       *a??     any string with "a" as its antepenultimate character

5. The GREETING Step

5.1 Initial Connection

5.1.1 Usage

   Responses
      200   Service available, posting allowed
      201   Service available, posting prohibited
      400   Service temporarily unavailable [1]
      502   Service permanently unavailable [1]

      These are the only valid response codes for the initial greeting;
      the server MUST not return any other generic response code.

   [1] Following a 400 or 502 response the server MUST immediately close
      the connection.

5.1.2 Description

   There is no command presented by the client upon initial connection
   to the server.  The server MUST present an appropriate response code
   as a greeting to the client.  This response informs the client about
   what steps the client should take to reach the news exchange step.

   If the server will accept further commands from the client including
   POST, the server MUST present a 200 greeting code.  If the server
   will accept further commands from the client, but it is not
     a*,c*,!*b  end with "b"
       ?a*      any string with "a" as its second character
       ??a*     any string with "a" as its third character
       *a?      any string with "a" as its penultimate character
       *a??     any string with "a" as its antepenultimate character

  6  Format for Keyword Descriptions

     On
   authorized to post articles using the following pages are descriptions of each keyword
     recognized by POST command, the server MUST
   present a 201 greeting code.

   Otherwise the NNTP server MUST present a 400 or 502 greeting code and then
   immediately close the responses that will connection.  502 MUST be
     returned by those commands. These keywords are grouped by used if the
     functional step in which they are used.

     Each keyword client is shown in upper case for clarity, although
   not permitted under any circumstances to interact with the
     NNTP server ignores case in the interpretation and
   400 otherwise.

5.1.3 Examples

   Example of commands.
     Parameters are shown as follows:

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        UPPERCASE    indicates literal text a normal connection from an authorized client which then
   jumps directly to be included in the
                     command;
        lowercase    indicates conclusion step (see Section 9):

      [Initial TCP connection setup completed.]
      [S] 200 NNTP Service Ready, posting permitted
      [C] QUIT
      [S] 205 NNTP Service exits normally
      [Server closes connection.]
   Example of a token described elsewhere;
        [brackets]   indicate normal connection from an authorized client that the parameter is optional;
        ellipsis...  indicates that not
   permitted to post; it also jumps directly to the parameter may be repeated
                     any number conclusion step:

      [Initial TCP connection setup completed.]
      [S] 201 NNTP Service Ready, posting prohibited
      [C] QUIT
      [S] 205 NNTP Service exits normally
      [Server closes connection.]

   Example of times (it must occur at least
                     once);
        vertical|bar indicates a choice normal connection from an unauthorized client:

      [Initial TCP connection setup completed.]
      [S] 502 NNTP Service permanently unavailable
      [Server closes connection.]

   Example of two mutually exclusive
                     parameters (exactly one must be provided).

     Parameters are case or language specific only when specified
     (either in this memo or in RFC 1036[7]).

     The name "wildmat" for a parameter indicates that it connection from a client where the server is unable to
   provide service:

      [Initial TCP connection setup completed.]
      [S] 400 NNTP Service temporarily unavailable
      [Server closes connection.]

5.2 MODE READER

5.2.1 Usage

   This command MUST NOT be pipelined.

   Syntax
      MODE READER

   Responses
      200   Posting allowed
      201   Posting prohibited
      400   Service temporarily unavailable [1]
      502   Service permanently unavailable [1]

   [1] Following a
     wildmat format pattern as defined in section 5. If 400 or 502 response the
     parameter does not meet server MUST immediately close
      the requirements of connection.

5.2.2 Description

   MODE READER SHOULD be sent by any client that section (for
     example, if it does not fit the grammar of 5.1) intends to use any
   command other than IHAVE, HEAD, STAT, LIST ACTIVE, LIST EXTENSIONS,
   or commands advertised by the NNTP server as available via LIST
   EXTENSIONS.

   Servers MAY place some interpretation on it (not specified by require that this memo) or otherwise MUST generate command be issued before any other
   commands are sent and MAY reject any other commands until after a 501 response.

  7   The GREETING Step

  7.1  Initial Connection

     There is no keyword presented by the client upon initial
     connection to the server.
   MODE READER command has been sent.

   The server MUST present an
     appropriate return a response code using the same codes as a the initial
   greeting (as described in Section 5.1.1) to indicate its ability to
   provide reading service to the client.  This
     response informs the client about what steps  Note that the client
     should take to reach response need
   not be the news exchange step.

     If same as the server will accept further commands from one presented during the client
     including POST, initial greeting.

   Once MODE READER is sent, IHAVE (and any extensions intended for
   peer-to-peer article transfer) MAY no longer be permitted, even if it
   were permitted before the server MUST present MODE READER command.  The results of LIST
   EXTENSIONS MAY be different following a 200 greeting code.
     If the server will accept further commands from MODE READER command than
   prior to the client,
     but issuing of that command.

   Servers are encouraged to not require this command even though
   clients SHOULD send it when appropriate.  It is not authorized to post articles using the POST
     command, the server MUST present a 201 greeting code.

     Otherwise the server MUST present a 400 or 502 greeting code
     and then immediately close the connection. 502 MUST be used
     if the client is not permitted under any circumstances to
     interact with the server and 400 otherwise.

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  7.1.1  Responses

         200 Service available, posting allowed
         201 Service available, posting prohibited
         400 Service temporarily unavailable
         502 Service unavailable

     Following support
   some news architectures that switch between modes based on whether a 400 or 502 response the
   given connection is a peer-to-peer connection with another server MUST immediately
     close the connection.

  7.1.2  Initial Connection Example or
   a news reading client.

5.2.3 Examples

   Example of a normal connection from use of the MODE READER command by an authorized client
          [Initial TCP connection setup completed.]
   which then jumps directly to the conclusion step (see Section 9):

      [C] Initial TCP connection completed MODE READER
      [S] 200 NNTP Service Ready, posting permitted
     Client can send commands at this point. In this example,
      [C] QUIT
      [S] 205 NNTP Service exits normally
      [Server closes connection.]

   Example of use of the MODE READER command by an authorized client
   that is not permitted to post; it also jumps directly to the
   conclusion step (See section
     10). step:

      [C] MODE READER
      [S] 201 NNTP Service Ready, posting prohibited
      [C] QUIT
      [S] 205 NNTP Service exits normally
      [Server closes connection.]

   Example of use of MODE READER by a normal connection from an unauthorized client not authorized to receive
   service from the server as a news reader:

      [C] Initial TCP connection completed MODE READER
      [S] 502 NNTP Service Unavailable permanently unavailable
      [Server closes connection.]
   Example of a normal connection from an authorized any client that
     is not permitted to post
          [Initial TCP connection setup completed.]
          [S] 201 NNTP Service Ready, posting prohibited
     Client can send commands at this point. In this example, where the
     client jumps directly server is unable to the conclusion step (See section
     10).
   provide news reader service:

      [C] QUIT
      [S] 205 400 NNTP Service exits normally temporarily unavailable
      [Server closes connection.]
     Example

6. The CAPABILITIES DISCOVERY step

   To discover what extensions are available, an NNTP client can query
   the server with the LIST EXTENSIONS command.  If a particular
   extension is unavailable, the client can attempt to work around it or
   it may wish to terminate the session.

   See Section 10 for further discussion of extensions.

6.1 LIST EXTENSIONS

6.1.1 Usage

   This command is optional.

   This command MUST NOT be pipelined.

   Syntax
      LIST EXTENSIONS

   Responses
      202   Extension list follows (multiline)
      402   Server has no extensions
      503   Extension information not available

6.1.2 Description

   The LIST EXTENSIONS command allows a connection from any client where the server is
     unable to provide service
          [Initial TCP connection setup completed.]
          [S] 400 NNTP Service temporarily unavailable
          [Server closes connection.]

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  7.2  MODE READER

     MODE READER
     MODE READER SHOULD determine which
   extensions are supported by the server.  This command MUST be sent
   implemented by any client server that intends to use implements any command other than IHAVE, HEAD, STAT, LIST, LIST
     EXTENSIONS, or commands advertised by extensions defined in
   this document.

   To discover what extensions are available, an NNTP client SHOULD
   query the server as available
     via early in the session for extensions information by
   issuing the LIST EXTENSIONS. EXTENSIONS command.  This command MAY be issued at
   anytime during a session.  It is not streamable.

     Servers MAY require required that the client issues
   this command be issued before attempting to make use of any
     other commands are sent and MAY reject any other commands
     until after a MODE READER command has been sent. extension.  The server MUST present a response using the same codes as
     the initial greeting (as described in section 7.1) to
     indicate its ability to provide reading service to the
     client.

     Clients SHOULD wait for a
   response to MODE READER after
     sending generated by this command and SHOULD MAY change during a session
   because of other state information.  However, an NNTP client MUST NOT send any additional
     commands until that response has been received from the
     server.

     Once MODE READER is sent, IHAVE (and
   cache (for use in another session) any extensions intended
     for peer-to-peer article transfer) MAY no longer be
     permitted, even information returned if it were permitted before the MODE READER
     command. The results of
   LIST EXTENSIONS MAY be different
     following a MODE READER command than prior succeeds.  That is, an NNTP client is only
   able to get the current and correct information concerning available
   extensions during a session by issuing of
     that command.

     Servers are encouraged to not require this a LIST EXTENSIONS command even
     though clients SHOULD send it when appropriate. It is present
     to support some news architectures
   during that switch between modes
     based on whether session and processing that response.

   The list of extensions is returned as a given connection multi-line response following
   the 202 response code.  Each extension is listed on a peer-to-peer
     connection separate line;
   the line MUST begin with another server or a news reading client.

  7.2.1  Responses
          200 Posting permitted
          201 Posting prohibited
          400 Service temporarily unavailable
          502 Service unavailable

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     Following a 400 an extension-label and optionally one or 502 response
   more parameters (separated by single spaces).  The extension-label
   and the meaning of the parameters are specified as part of the
   definition of the extension.  The extension-label MUST be in
   uppercase.

   The server MUST immediately
     close NOT list the connection.

     Note that same extension twice in the response,
   and MUST list all supported extensions.  The order in which the
   extensions are listed is not significant.  The server need not even
   consistently return the same order.  If the server does not support
   any extensions, a 402 response SHOULD be returned, but it MAY instead
   return an empty list.

   Following a 503 response need not an extension might still be available, and
   the same as the one
     presented during the initial greeting.

  7.2.2  MODE READER client MAY attempt to use it.

6.1.3 Examples

   Example of use of the MODE READER command by an authorized
     client a successful response:

      [C] MODE READER LIST EXTENSIONS
      [S] 200 NNTP Service Ready, posting permitted
     Client can send commands at this point. In this example, the
     client jumps directly to the conclusion step (See section
     10).
          [C] QUIT 202 Extensions supported:
      [S] 205 NNTP Service exits normally
          [Server closes connection.]
     Example of use OVER
      [S] HDR
      [S] LISTGROUP
      [S] .

   The particular extensions shown here are simply examples of MODE READER by a client not authorized what
   might be defined in other places, and no particular meaning should be
   attributed to
     receive service from the server as a news reader them.

   Example where no extensions are available, using preferred format:

      [C] MODE READER LIST EXTENSIONS
      [S] 502 Service Unavailable
          [Server closes connection.] 402 Server has no extensions

   Example of a normal connection from where no extensions are available, using an authorized client that
     is not permitted to post empty list:

      [C] MODE READER LIST EXTENSIONS
      [S] 201 NNTP Service Ready, posting prohibited
     Client can send commands at this point. In this example, the
     client jumps directly to the conclusion step (See section
     10).
          [C] QUIT 202 Extensions supported:
      [S] 205 NNTP Service exits normally
          [Server closes connection.]
     Example of .

7. Article posting and retrieval

   News reading clients have available a connection from any client where the server is
     unable variety of mechanisms to provide news reader service
          [C] MODE READER
          [S] 400 NNTP Service temporarily unavailable
          [Server closes connection.]

  8
   retrieve articles via NNTP.  The CAPABILITIES DISCOVERY Step

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     To discover what extensions news articles are available, stored and indexed
   using three types of keys.  One key is the message-id of an NNTP client can
     query article.
   According to RFC 1036, this identifier should be globally unique.
   Another key is composed of the newsgroup name and the article number
   within that newsgroup.  That key MUST be unique to a particular
   server (there will be only one article with the LIST EXTENSIONS command.
     If that number within a
   particular extension newsgroup), but is unavailable, not required to be globally unique.
   Additionally, because the client same article can
     attempt be cross-posted to work around it or it
   multiple newsgroups, there may wish be multiple keys that point to terminate the
     session.

     See section 12 for further discussion of extensions.

  8.1  LIST EXTENSIONS
   same article on the same server.  The LIST EXTENSIONS command allows a client to determine
     which extensions are supported by final key is the arrival
   timestamp, giving the time that the article arrived at the server. This command
     MUST be implemented by any

   The server MUST ensure that implements any
     extensions defined in this memo. This command is not
     streamable.

     To discover what extensions article numbers are available, an NNTP issued in order of
   arrival timestamp; that is, articles arriving later MUST have higher
   numbers than those that arrive earlier.  The server SHOULD allocate
   the next sequential unused number to each new article.

   Article numbers MUST lie between 1 and 4,294,967,295 inclusive.  The
   client and server SHOULD query NOT use leading zeroes in specifying article
   numbers, and MUST NOT use more than 16 digits.  In some situations,
   the server early value zero replaces an article number to show some special
   situation.

   Message-ids are as defined in RFC 2822 [7] with the session for extensions
     information by issuing the LIST EXTENSIONS command. This
     command MAY be issued at anytime during following
   modifications:

   o  A message-id MUST NOT contain a session.  It US-ASCII space within any
      quoted-pair.

   o  A message-id MUST NOT be longer than 250 octets.

   o  RFC 2822 obsolete syntax for message-ids is not
     required that supported by the client issues
      protocol specified in this command before
     attempting to make use of any extension. document.

7.1 Group and article selection

   The response
     generated following commands are used to set the "current selected
   newsgroup" and the "current article number", which are used by this command MAY change during a session because
   various commands.  At the start of other state information. However, an NNTP client MUST NOT
     cache (for use session, both of these
   values are set to the special value "invalid".

7.1.1 GROUP

7.1.1.1 Usage

   Syntax
      GROUP ggg

   Responses
      211 n l h ggg   Group successfully selected
      411             No such newsgroup

   Parameters
      ggg = name of newsgroup
      n   = estimated number of articles in another session) any information returned
     if the LIST EXTENSIONS command succeeds. That is, an NNTP
     client group
      l   = reported low water mark
      h   = reported high water mark

7.1.1.2 Description

   The required parameter ggg is only able to get the current and correct
     information concerning available extensions during a session
     by issuing a LIST EXTENSIONS command during that session and
     processing that response.

     A successful response starts with a 202 code and is followed
     by a name of the newsgroup to be
   selected (e.g.  "news.software.b").  A list of extensions, one per line. Each line MUST begin
     with an extension-label and optionally one or more parameters
     (separated valid newsgroups may
   be obtained by single spaces). using the LIST ACTIVE command (see Section 8.6.1).

   The extension-label and successful selection response will return the
     meaning article numbers of
   the parameters first and last articles in the group at the moment of selection
   (these numbers are specified referred to as part the "reported low water mark" and
   the "reported high water mark"), and an estimate of the
     definition number of
   articles on file in the extension. The extension-label group.

   If the group is not empty, the estimate MUST be in
     uppercase.

     The server at least the actual
   number of articles available, and MUST NOT list be no greater than one more
   than the same extension twice in difference between the
     response, reported low and MUST list all supported extensions. The order

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     in which high water marks.
   (Some implementations will actually count the extensions are listed is not significant. The
     server need not even consistently return number of articles on
   file.  Others will just subtract the same order.
     If low water mark from the server does not support any extensions, it SHOULD
     return a 402 failure response but MAY return high
   water mark and add one to get an empty list
     instead.

  8.1.1  Responses

          202  Extension list follows (multi-line response)
          400  Service temporarily unavailable
          402  Server has no extensions
          500  Unknown Command
          501  Syntax Error
          502  Program error, function not performed

     Following a 502 response estimate.)

   If the group is empty, one of the following three situations will
   occur.  Clients MUST accept all three cases; servers MUST NOT
   represent an extension might still empty group in any other way.

   o  The high water mark will be
     available, one less than the low water mark, and
      the client MAY attempt to estimated article count will be zero.  Servers SHOULD use it this
      method to show an empty group.  This is the only time that the
      high water mark can be less than the low water mark.

   o  All three numbers will be zero.

   o  The LIST EXTENSIONS command high water mark is optional, and a server MAY
     issue a 500 (unknown command) greater than or 501 (syntax error) response equal to it.
  8.1.1.1  LIST EXTENSIONS Examples

     Example of a successful response:
          [C] LIST EXTENSIONS
          [S] 202 Extensions supported:
          [S] OVER
          [S] HDR
          [S] LISTGROUP
          [S] . the low water
      mark.  The particular extensions shown here are simply examples of
     what estimated article count might be defined zero or non-zero; if
      non-zero, the same requirements apply as for a non-empty group.

   The set of articles in other places, and no particular
     meaning should a group may change after the GROUP command is
   carried out.  That is:

   o  articles may be attributed to them.
     Example where no extensions are available, using preferred
     format:
         [C] LIST EXTENSIONS
         [S] 402 Server has no extensions
     Example where removed from the group

   o  articles may be reinstated in the group with the same article
      number, but those articles MUST have numbers no extensions are available, using an empty
     list:
          [C] LIST EXTENSIONS
          [S] 202 Extensions supported:
          [S] .

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  9   The NEWS EXCHANGE Step

     During less than the
      reported low water mark (note that this step, two basic types is a reinstatement of transactions occur:
     * the
      previous article, not a new article retrieval from reusing the server
     * number)

   o  new articles may be added with article posting to numbers greater than the server

  9.1  Article Retrieval

     News reading clients
      reported high water mark (if an article that was the one with the
      highest number has been removed, the next new article will not
      have available a variety of mechanisms
     to retrieve articles via NNTP. The news articles are stored the number one greater than the reported high water mark)

   Except when the group is empty and indexed using all three types of keys. One key numbers are zero,
   whenever a subsequent GROUP command for the same newsgroup is issued,
   either by the message
     id same client or a different client, the reported low
   water mark in the response MUST be no less than that in any previous
   response for that newsgroup sent to any client.  The client may make
   use of an article. According the low water mark to RFC 1036, this identifier
     should be globally unique. Another key remove all remembered information about
   articles with lower numbers, as these will never recur.  This
   includes the situation when the high water mark is composed of one less than the
     newsgroup name and
   low water mark.

   No similar assumption can be made about the high water mark, as this
   can decrease if an article number within that newsgroup.
     That key is removed, and then increase again if it
   is reinstated or if new articles arrive.  When a valid group is
   selected by means of this command, the current selected newsgroup
   MUST be unique set to a particular server (there will be
     only one article with that number within a particular
     newsgroup), but is not required to be globally unique.
     Additionally, because group and the same current article can be cross-posted to
     multiple newsgroups, there may number MUST be multiple keys that point set
   to the same first article on in the same server. The final key group.  If an empty newsgroup is
   selected, the
     arrival timestamp, giving the time that the article arrived
     at the server.

     The server MUST ensure that current article numbers are issued in
     order of arrival timestamp; that is, articles arriving later
     MUST have higher numbers than those that arrive earlier. The
     server SHOULD allocate pointer is made invalid.  If an invalid
   group is specified, the next sequential unused number to
     each new article.

     Article numbers MUST lie between 1 and 4,294,967,295
     inclusive. The client and server SHOULD NOT use leading
     zeroes in specifying article numbers, current selected newsgroup and MUST NOT use more
     than 16 digits. In some situations, the value zero replaces
     an current
   article number to show some special situation.

     Message ids are defined in RFC 2822 with the following
     modifications:
     *  A message id MUST NOT contain a US-ASCII space within any
        quoted-pair.
     *  A message id MUST NOT be longer than 250 octets.

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     *  RFC 2822 obsolete syntax for message ids are not supported
        by changed.

   The GROUP command (or the protocol specified in this memo.

  9.1.1 Article Retrieval LISTGROUP command, if implemented) MUST be
   used by Newsgroup Name a client and Article Number

     The following commands are a successful response received before the any
   other command is used to set that depends on the value of the current
   selected newsgroup
     name and the "current or current article pointer" which number.

   If the group specified is used by other
     commands not available on the server, a 411 response
   MUST be returned.

7.1.1.3 Examples

   Example for article retrieval. At a group known to the start server:

      [C] GROUP misc.test
      [S] 211 1234 3000234 3002322 misc.test

   Example for a group unknown to the server:

      [C] GROUP example.is.sob.bradner.or.barber
      [S] 411 example.is.sob.bradner.or.barber is unknown

   Example of an NNTP
     session, both empty group using the preferred response:

      [C] GROUP example.currently.empty.newsgroup
      [S] 211 0 4000 3999 example.currently.empty.newsgroup

   Example of these values are undefined.
  9.1.1.1 an empty group using an alternative response:

      [C] GROUP example.currently.empty.newsgroup
      [S] 211 0 0 0 example.currently.empty.newsgroup

   Example of an empty group using a different alternative response:

      [C] GROUP ggg
     The required parameter ggg example.currently.empty.newsgroup
      [S] 211 0 4000 4321 example.currently.empty.newsgroup

7.1.2 LAST

7.1.2.1 Usage

   Syntax
      LAST

   Responses
      223 n message-id   Article found
      412                No newsgroup selected
      420                Current article number is invalid
      422                No previous article in this group

   Parameters
      n          = article number
      message-id = article message-id

7.1.2.2 Description

   If the name of the newsgroup to be current selected (e.g. "news.software.b"). A list of valid newsgroups
     may newsgroup is valid, the current article
   number MUST be obtained by using set to the LIST keyword.  See section 9.4
     for more information on previous article in that newsgroup (that
   is, the LIST keyword.

     The successful selection response will return highest existing article number less than the current article
     numbers of
   number).  If successful, a response indicating the first new current
   article number and last articles the message-id of that article MUST be returned.
   No article text is sent in response to this command.

   There MAY be no previous article in the group at group, although the current
   article number is not the reported low water mark.  There MUST NOT be
   a previous article when the
     moment of selection (these numbers are referred to as current article number is the
     "reported reported
   low water mark" mark.

   Because articles can be removed and added, the "reported high water
     mark"), results of multiple
   LAST and an estimate NEXT commands MAY not be consistent over the life of a
   particular NNTP session.

   If the current article number is already the first article of articles on file in the group.
   newsgroup, a 422 response MUST be returned.  If the group current article
   number is not empty, invalid, a 420 response MUST be returned.  If the estimate current
   selected newsgroup is invalid, a 412 response MUST be at least returned.  In
   all three cases the
     actual number of articles available, current selected newsgroup and current article
   number MUST NOT be no greater
     than one more than altered.

7.1.2.3 Examples

   Example of a successful article retrieval using LAST:

      [C] GROUP misc.test
      [S] 211 1234 3000234 3002322 misc.test
      [C] NEXT
      [S] 223 3000237 <668929@example.org> retrieved
      [C] LAST
      [S] 223 3000234 <45223423@example.com> retrieved

   Example of an attempt to retrieve an article without having selected
   a group (via the difference between GROUP command) first:

      [Assumes current selected newsgroup is invalid.]
      [C] LAST
      [S] 412 no newsgroup selected

   Example of an attempt to retrieve an article using the reported low
     and high water marks. (Some implementations will actually
     count LAST command
   when the current article number is that of articles on file. Others will just
     subtract the low water mark from first article in the high water mark and add
     one
   group:

      [C] GROUP misc.test
      [S] 211 1234 3000234 3002322 misc.test
      [C] LAST
      [S] 422 No previous article to retrieve

   Example of an attempt to get retrieve an estimate.)

     If article using the group is empty, one of LAST command
   when the following three situations
     will occur. Clients MUST accept all three cases; servers MUST
     NOT represent an empty group current selected newsgroup is empty:

      [C] GROUP example.empty.newsgroup
      [S] 211 0 0 0 example.empty.newsgroup
      [C] LAST
      [S] 420 No current article selected

7.1.3 NEXT

7.1.3.1 Usage

   Syntax
      NEXT

   Responses
      223 n message-id   Article found
      412                No newsgroup selected
      420                Current article number is invalid
      421                No next article in any other way.

     The high water mark will be one less than this group

   Parameters
      n          = article number
      message-id = article message-id

7.1.3.2 Description

   If the low water mark,
     and current selected newsgroup is valid, the estimated current article count will
   number MUST be zero. Servers SHOULD
     use this method set to show an empty group. This is the only time next article in that newsgroup (that is,
   the high water mark can be less than the low water mark.
     All three numbers will be zero.

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     The high water mark is lowest existing article number greater than or equal to the low water
     mark; the estimated current article count might be zero or non-zero;
     if non-zero, the same requirements apply as for a non-empty
     group.

     The set of articles in
   number).  If successful, a group may change after response indicating the GROUP
     command is carried out. That is:
     *  articles may be removed from new current
   article number and the group
     *  articles may message-id of that article MUST be reinstated returned.
   No article text is sent in response to this command.

   If the group with current article number is already the same last article number, but those articles of the
   newsgroup, a 421 response MUST have numbers no
        less than be returned.  In all other aspects
   (apart, of course, from the reported low water mark (note that lack of 422 response) this command is a
        reinstatement of
   identical to the previous article, not LAST command (Section 7.1.2).

7.1.3.3 Examples

   Example of a new successful article
        reusing the number)
     *  new articles may be added with retrieval using NEXT:

      [C] GROUP misc.test
      [S] 211 1234 3000234 3002322 misc.test
      [C] NEXT
      [S] 223 3000237 <668929@example.org> retrieved

   Example of an attempt to retrieve an article numbers greater
        than without having selected
   a group (via the reported high water mark (if GROUP command) first:

      [Assumes current selected newsgroup is invalid.]
      [C] NEXT
      [S] 412 no newsgroup selected

   Example of an attempt to retrieve an article that was
        the one with using the highest number has been removed, NEXT command
   when the next
        new current article will not have the number one greater than is that of the
        reported high water mark)

     Except when last article in the group is empty and all three numbers are
     zero, whenever a subsequent
   group:

      [C] GROUP misc.test
      [S] 211 1234 3000234 3002322 misc.test
      [C] STAT 3002322
      [S] 223 3002322 <411@example.net> retrieved
      [C] NEXT
      [S] 421 No next article to retrieve

   Example of an attempt to retrieve an article using the NEXT command for
   when the same current selected newsgroup is issued, either by the same client or a different
     client, the reported low water mark empty:

      [C] GROUP example.empty.newsgroup
      [S] 211 0 0 0 example.empty.newsgroup
      [C] NEXT
      [S] 420 No current article selected

7.2 Retrieval of articles and article sections

   The ARTICLE, BODY, HEAD, and STAT commands are very similar.  They
   differ only in the response MUST be
     no less than parts of the article that are presented to the
   client and in any previous the successful response for that newsgroup
     sent to any client. code.  The client may make use ARTICLE command is
   described here in full, while the other commands are described in
   terms of the low water
     mark to remove all remembered information about articles with
     lower numbers, differences.  An article, as these will never recur. This includes defined by RFC 1036,
   consists of two parts: the
     situation when article headers and the high water mark is article body.
   When responding to one less than of these commands, the low
     water mark.

     No similar assumption can be made about server presents the high water mark,
     as this can decrease if an
   entire article is removed, or appropriate part and then
     increase again if it is reinstated does not attempt to alter or if new articles arrive.
     When a valid group is
   translate it in any way.

7.2.1 ARTICLE

7.2.1.1 Usage

   Syntax
      ARTICLE message-id
      ARTICLE [number]
   Responses

      First form (message-id specified)
         220 0 message-id   Article follows (multiline)
         430                No article found with that message-id

      Second form (optional article number specified)
         220 n message-id   Article follows (multiline)
         412                No newsgroup selected by means of this command, the
     internally maintained "current
         420                Current article pointer" MUST be set
     to the first number is invalid [1]
         423                No such article in this newsgroup

   Parameters
      number     = Requested article number
      n          = Returned article number
      message-id = Article message-id

   [1] The 420 response can only occur if no article number has been
      specified.

7.2.1.2 Description

   The ARTICLE command selects an article based on the arguments and
   presents the group header, a blank line, and the name body of that article.  The
   command has two forms.

   In the current
     newsgroup MUST be set to the selected newsgroup name. If an
     invalid group first form, a message-id is specified, specified (including the previously selected group, if
     any, angle
   brackets), and article MUST remain selected. If an empty newsgroup
     is selected, the "current server presents the article pointer" is with that message-id
   in an
     indeterminate state and MUST NOT be used.

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     The GROUP keyword (or its headers.  In this case, the LISTGROUP keyword, if implemented) server MUST be used by a client and a successful response received
     before the any other command is used that depends on having NOT alter the "current current
   selected newsgroup or current article pointer" be valid.

     If the group specified number.  This is not available on both to
   facilitate the server, it
     MUST return a 411 error code.

  9.1.1.1.1  Responses

            211 n l h ggg Group successfully selected (n =
                          estimated number presentation of articles in the
                          group, l = low water mark, h = high
                          water mark, ggg = name that may be referenced within
   another article being read, and because of the group
            411           No such newsgroup

  9.1.1.1.2  GROUP Examples

     Example for a group known to semantic difficulties
   of determining the server
          [C] GROUP misc.test
          [S] 211 1234 3000234 3002322 misc.test

     Example for a group unknown proper sequence and membership of an article that
   may have been crossposted to more than one newsgroup.

   In the server
          [C] GROUP example.is.sob.bradner.or.barber
          [S] 411 example.is.sob.bradner.or.barber is unknown
  9.1.1.2   LAST

     LAST
     If the current newsgroup is valid, response, the internally maintained
     "current article pointer" MUST be set number is replaced with zero (that is,
   the server is not required to determine whether the previous article is in the
   current newsgroup.  If already positioned at the first group or what article of number(s) it has).

   In the newsgroup, second form, an error message MUST article number may be returned specified.  If so, and the current
   if there is an article with that number in the currently selected
   newsgroup, the server MUST remain selected.

     There MAY be no previous set the current article in number to that
   number.

   Then, whether or not a number was specified, the group, although article indicated by
   the current article number is not presented to the client.

   Note that a previously valid article number MAY become invalid if the
   article has been removed.  A previously invalid article number MAY
   become valid if the article has been reinstated, but such an article
   number MUST be no less than the reported low water mark.
     There mark for that
   group.

   The server MUST NOT be change the current selected newsgroup as a previous article when result
   of this command.  The server MUST NOT change the current article
   number is the reported low water mark.

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     Because articles can be removed except when an article number argument was provided and added, the results
   article exists; in particular, it MUST NOT change it following an
   unsuccessful response.

   The message-id of
     multiple LAST and NEXT commands MAY not the article is taken from the message-id header
   line of the article (required by RFC 1036).  If there is no such
   line, the message-id "<0>" MUST be consistent over used instead (without the life double
   quotes).

   Since the message-id field is unique for each article, it may be used
   by a client to skip duplicate displays of articles that have been
   posted more than once, or to more than one newsgroup.

   The article headers and body are returned as a particular NNTP session.

     If successful, a multi-line response indicating
   following the 220 response code.

   If the current article number and is invalid, a message-id string 420 response MUST be
   returned. No article
     text  If there is sent in response to this command.
  9.1.1.2.1  Responses

            223 n a   Article found (n = no article with the specified number, a = message-id)
            412       No newsgroup 423
   response MUST be returned.  If the current selected
            420       Current article pointer newsgroup is invalid
            422       No previous article in this group

  9.1.1.2.2  LAST
   invalid, a 412 response MUST be returned.

7.2.1.3 Examples

   Example of a successful article retrieval using LAST
          [S] 200 NNTP Service Ready of an article (using no article
   number):

      [C] GROUP misc.test
      [S] 211 1234 3000234 3002322 misc.test
      [C] NEXT
          [S] 223 3000237 <668929@example.org> retrieved
          [C] LAST ARTICLE
      [S] 223 220 3000234 <45223423@example.com> retrieved
      [S] Path: pathost!demo!whitehouse!not-for-mail
      [S] From: "Demo User" <nobody@example.net>
      [S] Newsgroups: misc.test
      [S] Subject: I am just a test article
      [S] Date: 6 Oct 1998 04:38:40 -0500
      [S] Organization: An Example Net, Uncertain, Texas
      [S] Message-ID: <411@example.net>
      [S]
      [S] This is just a test article.
      [S] .

   Example of an attempt to retrieve a successful retrieval of an article without having
     selected by message-id:

      [C] ARTICLE <45223423@example.com>
      [S] 220 0 <45223423@example.com>
      [S] Path: pathost!demo!whitehouse!not-for-mail
      [S] From: "Demo User" <nobody@example.net>
      [S] Newsgroups: misc.test
      [S] Subject: I am just a group (via the GROUP command) first test article
      [S] 200 NNTP Service ready Date: 6 Oct 1998 04:38:40 -0500
      [S] Organization: An Example Net, Uncertain, Texas
      [S] Message-ID: <411@example.net>
      [S]
      [S] This is just a test article.
      [S] .

   Example of an unsuccessful retrieval of an article by message-id:

      [C] LAST ARTICLE <i.am.not.there@example.com>
      [S] 412 no newsgroup selected 430 No Such Article Found

   Example of an attempt to retrieve unsuccessful retrieval of an article using the LAST
     command when the current article pointer is pointing at the
     first article in the group
          [S] 200 NNTP Service Ready by number:

      [C] GROUP misc.test
      [S] 211 1234 3000234 3002322 misc.test news.groups
      [C] LAST ARTICLE 300256
      [S] 422 423 No previous such article to retrieve number in this group

   Example of an unsuccessful retrieval of an article by number because
   no newsgroup was selected first:

      [Assumes current selected newsgroup is invalid.]
      [C] ARTICLE 300256
      [S] 412 No newsgroup selected

   Example of an attempt to retrieve an article using the LAST
     command when the current group
   selected newsgroup is empty

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          [S] 200 NNTP Service Ready empty:

      [C] GROUP example.empty.newsgroup
      [S] 211 0 0 0 example.empty.newsgroup
      [C] LAST ARTICLE
      [S] 420 No current article selected
  9.1.1.3  NEXT

     NEXT
     If the current newsgroup is valid, the internally maintained
     "current article pointer" MUST be advanced to the next
     article in the current newsgroup.  If no more articles remain
     in the current group, an error message MUST be returned and
     the current article MUST remain selected.

     If successful, a response indicating the current article
     number and the

7.2.2 HEAD

7.2.2.1 Usage
   Syntax
      HEAD message-id string MUST be returned.
      HEAD [number]

   Responses

      First form (message-id specified)
         221 0 message-id   Headers follow (multiline)
         430                No article text is sent in response to this command.

  9.1.1.3.1  Responses

            223 n a   Article found (n = number, a = message-id) with that message-id

      Second form (optional article number specified)
         221 n message-id   Headers follow (multiline)
         412                No newsgroup selected
         420                Current article pointer number is invalid
            421 [1]
         423                No next such article in this group

  9.1.1.3.2  NEXT newsgroup

   Parameters
      number     = Requested article number
      n          = Returned article number
      message-id = Article message-id

   [1] The 420 response can only occur if no article number has been
      specified.

7.2.2.2 Description

   The HEAD command behaves identically to the ARTICLE command except
   that, if the article exists, the response code is 221 instead of 220
   and only the headers are presented (the blank line separating the
   headers and body MUST NOT be included).

7.2.2.3 Examples

   Example of a successful article retrieval using NEXT
          [S] 200 NNTP Service Ready
          [C] GROUP misc.test
          [S] 211 1234 3000234 3002322 misc.test
          [C] NEXT
          [S] 223 3000237 <668929@example.org> retrieved
     Example of an attempt to retrieve an article without having
     selected a group (via the GROUP command) first
          [S] 200 NNTP Service ready
          [C] NEXT
          [S] 412 no newsgroup selected

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     Example of an attempt to retrieve headers in an article using the NEXT
     command when the current article pointer is pointing at the
     last (using
   no article in the group
          [S] 200 NNTP Service Ready number):

      [C] GROUP misc.test
      [S] 211 1234 3000234 3002322 misc.test
      [C] ARTICLE 3002322 HEAD
      [S] 220 3002322 <411@example.net> retrieved 221 3000234 <45223423@example.com>
      [S] Path: pathost!demo!whitehouse!not-for-mail
      [S] From: ˘Demo User÷ "Demo User" <nobody@example.net>
      [S] Newsgroups: misc.test
      [S] Subject: I am just a test article
      [S] Date: 6 Oct 1998 04:38:40 -0500
      [S] Organization: An Example Net, Uncertain, Texas
      [S] Message-ID: <411@example.net>
      [S] .

   Example of a successful retrieval of the headers in an article by
   message-id:

      [C] HEAD <45223423@example.com>
      [S] 221 0 <45223423@example.com>
      [S] Path: pathost!demo!whitehouse!not-for-mail
      [S] This is From: "Demo User" <nobody@example.net>
      [S] Newsgroups: misc.test
      [S] Subject: I am just a test article. article
      [S] Date: 6 Oct 1998 04:38:40 -0500
      [S] Organization: An Example Net, Uncertain, Texas
      [S] Message-ID: <411@example.net>
      [S] .

   Example of an unsuccessful retrieval of the header of an article by
   message-id:

      [C] NEXT HEAD <i.am.not.there@example.com>
      [S] 421 430 No next Such Article Found

   Example of an unsuccessful retrieval of the header of an article to retrieve by
   number:

      [C] GROUP misc.test
      [S] 211 1234 3000234 3002322 misc.test
      [C] HEAD 300256
      [S] 423 No such article number in this group

   Example of an unsuccessful retrieval the header of an article by
   number because no newsgroup was selected first:

      [Assumes current selected newsgroup is invalid.]
      [C] HEAD 300256
      [S] 412 No newsgroup selected

   Example of an attempt to retrieve the header of an article using the NEXT
     command when the
   current group selected newsgroup is empty
          [S] 200 NNTP Service Ready empty:

      [C] GROUP example.empty.newsgroup
      [S] 211 0 0 0 example.empty.newsgroup
      [C] NEXT HEAD
      [S] 420 No current article selected

  9.2  Retrieval of Articles and Article Sections

     The ARTICLE, BODY, HEAD, and STAT commands are very similar.
     They differ only in the parts of the

7.2.3 BODY

7.2.3.1 Usage

   Syntax
      BODY message-id
      BODY [number]

   Responses

      First form (message-id specified)
         222 0 message-id   Body follows (multiline)
         430                No article found with that are
     presented to the client and in the successful response code.
     The ARTICLE command is described here in full, while the
     other commands are described in terms of the differences.
     An article, as defined by RFC 1036, consists of two parts:
     the message-id

      Second form (optional article headers and the number specified)
         222 n message-id   Body follows (multiline)
         412                No newsgroup selected
         420                Current article body. When responding to
     one of these commands, the server presents the entire number is invalid [1]
         423                No such article
     or appropriate part and does not attempt to alter or
     translate it in any way.

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  9.2.1  ARTICLE

     ARTICLE <message-id>
     ARTICLE [number] this newsgroup

   Parameters
      number     = Requested article number
      n          = Returned article number
      message-id = Article message-id

   [1] The ARTICLE command selects an 420 response can only occur if no article based on the arguments
     and presents the header, a blank line, and the body of that
     article. number has been
      specified.

7.2.3.2 Description

   The BODY command has two forms.

     In the first form, a message-id is specified (including the
     angle brackets), and the server presents the article with
     that message-id in its headers. In this case, behaves identically to the server MUST
     NOT alter ARTICLE command except
   that, if the "current article pointer". This is both to
     facilitate exists, the presentation response code is 222 instead of articles that may be
     referenced within another article being read, 220
   and because of only the semantic difficulties of determining body is presented (the blank line separating the proper sequence headers
   and membership body MUST NOT be included).

7.2.3.3 Examples

   Example of a successful retrieval of an article that may have been crossposted
     to more than one newsgroup.

     In the second form, an article number may be specified. If
     so, and if there is body of an article with that number in the
     currently selected group, the server MUST set the current (using no
   article pointer to that number.

     Then, whether or not number):

      [C] GROUP misc.test
      [S] 211 1234 3000234 3002322 misc.test
      [C] BODY
      [S] 222 3000234 <45223423@example.com>
      [S] This is just a number was specified, test article.
      [S] .

   Example of a successful retrieval of the body of an article
     indicated by the current article pointer
   message-id:

      [C] BODY <45223423@example.com>
      [S] 222 0 <45223423@example.com>
      [S] This is presented to the
     client.

     Note that just a previously valid article number MAY become
     invalid if test article.
      [S] .

   Example of an unsuccessful retrieval of the body of an article has been removed. A previously invalid
     article number MAY become valid if by
   message-id:

      [C] BODY <i.am.not.there@example.com>
      [S] 430 No Such Article Found

   Example of an unsuccessful retrieval of the article has been
     reinstated, but such body of an article number MUST be no less than
     the reported low water mark for that group.

     The server MUST NOT change the currently selected by
   number:

      [C] GROUP misc.test
      [S] 211 1234 3000234 3002322 misc.test
      [C] BODY 300256
      [S] 423 No such article number in this group as a
     result

   Example of an unsuccessful retrieval of this command. The server MUST NOT change the
     current selected article except when body of an article by
   number
     argument because no newsgroup was provided and selected first:

      [Assumes current selected newsgroup is invalid.]
      [C] BODY 300256
      [S] 412 No newsgroup selected

   Example of an attempt to retrieve the article exists; in particular,
     it MUST NOT change it following body of an unsuccessful response.
  9.2.1.1 article when the
   current selected newsgroup is empty:

      [C] GROUP example.empty.newsgroup
      [S] 211 0 0 0 example.empty.newsgroup
      [C] BODY
      [S] 420 No current article selected

7.2.4 STAT

7.2.4.1 Usage

   Syntax
      STAT message-id
      STAT [number]
   Responses

      First form (message-id specified):

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            220 specified)
         223 0 a message-id   Article follows (multi-line response, a =
                     message-id) exists
         430                No article found with that message-id
            502      Program error, function not performed

      Second form (optional article number specified):

            220 specified)
         223 n a message-id   Article follows (multi-line response, n =
                     article number, a = message-id) exists
         412                No newsgroup selected
         420      No current                Current article selected number is invalid [1]
         423                No such article in this newsgroup
            502      Program error, function not performed

   Parameters
      number     = Requested article number
      n          = Returned article number
      message-id = Article message-id

   [1] The 420 response can only occurs occur if no article number has been
      specified.

     In the 220 response, the first parameter is 0 for the first
     form and the article number (within the current group) for
     the second form.

7.2.4.2 Description

   The second parameter is the message-id of
     the article (within angle brackets). This is taken from STAT command behaves identically to the
     message-id header line of ARTICLE command except
   that, if the article (required by RFC 1036).
     If there is no such line, the message-id "<0>" MUST be used
     instead (without the double quotes).

     Since the message-id field is unique for each article, it may
     be used by a client exists, it is NOT presented to skip duplicate displays the client and
   the response code is 223 instead of articles 220.  Note that have been posted more than once, or the response is
   NOT multi-line.

   This command allows the client to more than one
     newsgroup.

     The determine whether an article headers
   exists, and body are returned as a multi-line
     response following in the initial response line.
  9.2.1.2 second form what its message-id is, without having
   to process an arbitrary amount of text.

7.2.4.3 Examples

   Example of a successful retrieval of STAT on an existing article (using no article number)
          [S] 200 NNTP Service Ready number):

      [C] GROUP misc.test
      [S] 211 1234 3000234 3002322 misc.test
      [C] ARTICLE STAT
      [S] 220 223 3000234 <45223423@example.com>

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          [S] Path: pathost!demo!somewhere!not-for-mail
          [S] From: ˘Demo User÷ <nobody@example.com>
          [S] Newsgroups: misc.test
          [S] Subject: I am just a test article
          [S] Date: 6 Oct 1998 04:38:40 -0500
          [S] Organization: An Example Com, San Jose, CA
          [S] Message-ID: <45223423@example.com>
          [S]
          [S] This is just a test article.
          [S] .

   Example of a successful retrieval STAT of an existing article by message-id
          [S] 200 NNTP Service Ready message-id:

      [C] ARTICLE STAT <45223423@example.com>
      [S] 220 223 0 <45223423@example.com>
          [S] Path: pathost!demo!somewhere!not-for-mail
          [S] From: ˘Demo User÷ <nobody@example.com>
          [S] Newsgroups: misc.test
          [S] Subject: I am just a test article
          [S] Date: 6 Oct 1998 04:38:40 -0500
          [S] Organization: An Example Com, San Jose, CA
          [S] Message-ID: <45223423@example.com>
          [S]
          [S] This is just a test article.
          [S] .

   Example of an unsuccessful retrieval STAT of an article not on the server by
     message-id
          [S] 200 NNTP Service Ready message-id:

      [C] ARTICLE STAT <i.am.not.there@example.com>
      [S] 430 No Such Article Found

   Example of an unsuccessful retrieval STAT of an article not in the server by number
          [S] 200 NNTP Service Ready number:

      [C] GROUP misc.test
      [S] 211 1234 3000234 3002322 news.groups misc.test
      [C] ARTICLE STAT 300256
      [S] 423 No such article number in this group

   Example of an unsuccessful retrieval STAT of an article by number
     because when no newsgroup was
   selected first
          [S] 200 NNTP Service Ready first:

      [Assumes current selected newsgroup is invalid.]
      [C] ARTICLE STAT 300256
      [S] 412 No newsgroup selected

   Example of an attempt to retrieve STAT of an article when the current
     group selected newsgroup is empty

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          [S] 200 NNTP Service Ready
   empty:

      [C] GROUP example.empty.newsgroup
      [S] 211 0 0 0 example.empty.newsgroup
      [C] ARTICLE STAT
      [S] 420 No current article selected
     Example

7.3 Article posting

   Article posting is done in one of two modes: individual article
   posting from news reading clients using POST, and article transfer
   from other news servers using IHAVE.

7.3.1 POST

7.3.1.1 Usage

   This command MUST NOT be pipelined.

   Syntax
      POST

   Responses

      Initial responses
         340   Send article to be posted
         440   Posting not permitted
      Subsequent responses
         240   Article received OK
         441   Posting failed

7.3.1.2 Description

   If posting is allowed, a failure due 340 response MUST be returned to indicate
   that the service being unavailable
          [S] 200 NNTP Service Ready
          [C] ARTICLE <i.am.a.test.article@example.com>
          [S] 502 Service unavailable

  9.2.2  HEAD

     HEAD <message-id>
     HEAD [number] article to be posted should be sent.  If posting is
   prohibited for some installation-dependent reason, a 440 response
   MUST be returned.

   If posting is permitted, the article MUST be presented to the server
   by the client in the format specified by RFC 1036 (or by any of its
   successors or extensions).  The HEAD command behaves identically text forming the header and body of
   the message to be posted MUST be sent by the client in the format
   defined above (Section 3) for multi-line responses (except that there
   is no initial line containing a response code).  Thus a single dot
   (".") on a line indicates the end of the text, and lines starting
   with a dot in the original text have that dot doubled during
   transmission.

   Following the presentation of the termination sequence by the client,
   the server MUST return a response indicating success or failure of
   the article transfer.  Note that response codes 340 and 440 are used
   in direct response to the ARTICLE command
     except POST command.  Others are returned
   following the sending of the article.

   A response of 240 SHOULD indicate that, if barring unforseen server
   errors, the posted article exists, only will be made available on the headers are
     presented (the blank line separating server and/
   or transferred to other servers as appropriate.  In other words,
   articles not wanted by the headers and body
     MUST NOT server SHOULD be included).
  9.2.2.1  Responses

     First form (message-id specified):

            221 0 a  Article follows (multi-line response, rejected with a =
                     message-id)
            430 411
   response and not accepted and silently discarded.

   No article found with attempt shall be made by the server to filter characters, fold or
   limit lines, or otherwise process incoming text.  The intent is that message-id
            502      Program error, function
   the server just passes the incoming message to be posted to the
   server installation's news posting software, which is not performed

     Second form (optional article number specified):

            221 n a  Article follows (multi-line response, n =
                     article number, a = message-id)
            412      No newsgroup selected
            420      No current article selected
            423      No such article in defined by
   this newsgroup
            502      Program error, function not performed

     Except document.

   The client SHOULD NOT assume that only the headers are included in article has been successfully
   transferred unless it receives an affirmative response from the response,
   server.  If the 221 response behaves identically to session is interrupted before the 220 response of is
   received, it is possible that an affirmative response was sent but
   has been lost.  Therefore, in any subsequent session the ARTICLE command.

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  9.2.2.2 client
   SHOULD use the same message-id in the article when resending it or
   check whether the article was successfully posted before resending it
   to ensure that the resend will not result in a duplicate article.

7.3.1.3 Examples

   Example of a successful retrieval of the headers in an
     article (using no article number)
          [S] 200 NNTP Service Ready posting:

      [C] GROUP misc.test POST
      [S] 211 1234 3000234 3002322 misc.test 340 Input article; end with <CR-LF>.<CR-LF>
      [C] HEAD
          [S] 221 3000234 <45223423@example.com>
          [S] Path: pathost!demo!somewhere!not-for-mail
          [S] From: ˘Demo User÷ <nobody@example.com>
          [S] "Demo User" <nobody@example.net>
      [C] Newsgroups: misc.test
          [S]
      [C] Subject: I am just a test article
          [S] Date: 6 Oct 1998 04:38:40 -0500
          [S]
      [C] Organization: An Example Com, San Jose, CA
          [S] Message-ID: <45223423@example.com>
          [S] Net
      [C]
      [C] This is just a test article.
      [C] .
      [S] 240 Article received OK

   Example of a successful retrieval of the headers in an
     article by message-id
          [S] 200 NNTP Service Ready unsuccessful posting:

      [C] HEAD <45223423@example.com>
          [S] 221 0 <45223423@example.com>
          [S] Path: pathost!demo!somewhere!not-for-mail POST
      [S] 340 Input article; end with <CR-LF>.<CR-LF>
      [C] From: ˘Demo User÷ <nobody@example.com>
          [S] "Demo User" <nobody@example.net>
      [C] Newsgroups: misc.test
          [S]
      [C] Subject: I am just a test article
          [S] Date: 6 Oct 1998 04:38:40 -0500
          [S]
      [C] Organization: An Example Com, San Jose, CA
          [S] Message-ID: <45223423@example.com>
          [S] .
     Example of an unsuccessful retrieval of the header of an
     article by message-id
          [S] 200 NNTP Service Ready
          [C] HEAD <i.am.not.there@example.com>
          [S] 430 No Such Article Found
     Example of an unsuccessful retrieval of the header of an
     article by number
          [S] 200 NNTP Service Ready Net
      [C] GROUP misc.test
          [S] 211 1234 3000234 3002322 misc.test
      [C] HEAD 300256
          [S] 423 No such article number in this group

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     Example of an unsuccessful retrieval the header of an article
     by number because no newsgroup was selected first
          [S] 200 NNTP Service Ready This is just a test article.
      [C] HEAD 300256
          [S] 412 No newsgroup selected .
      [S] 441 Posting failed

   Example of an attempt to retrieve the header of an article post when the current group selected posting is empty
          [S] 200 NNTP Service Ready
          [C] GROUP example.empty.newsgroup
          [S] 211 0 0 0 example.empty.newsgroup not allowed:

      [C] HEAD
          [S] 420 No current article selected
     Example of a failure due to the service being unavailable MODE READER
      [S] 200 201 NNTP Service Ready Ready, posting prohibited
      [C] HEAD <i.am.a.test.article@example.com> POST
      [S] 502 Service unavailable

  9.2.3  BODY

     BODY <message-id>
     BODY [number]
     The BODY command behaves identically to the ARTICLE 440 Posting not permitted

7.3.2 IHAVE

7.3.2.1 Usage

   This command
     except that, if the article exists, only the body is
     presented (the blank line separating the headers and body MUST NOT be included).
  9.2.3.1 pipelined.

   Syntax
      IHAVE message-id

   Responses

     First form (message-id specified):

            222 0 a
      Initial responses
         335   Send article to be transferred
         435   Article follows (multi-line response, a not wanted
         436   Transfer not possible; try again later

      Subsequent responses
         235   Article transferred OK
         436   Transfer failed; try again later
         437   Transfer rejected; do not retry

   Parameters
      message-id =
                     message-id)
            430      No Article message-id

7.3.2.2 Description

   The IHAVE command informs the server that the client has an article found
   with the specified message-id.  If the server desires a copy of that message-id
            502      Program error, function not performed

     Second form (optional
   article number specified):

            222 n a  Article follows (multi-line response, n = 335 response MUST be returned, instructing the client to
   send the entire article.  If the server does not want the article number,
   (if, for example, the server already has a = message-id)
            412      No newsgroup selected
            420      No current article selected
            423      No such article in this newsgroup

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            502      Program error, function not performed

     Except copy of it), a 435
   response MUST be returned, indicating that only the body article is included in the response, not wanted.
   Finally, if the
     222 response behaves identically to article isn't wanted immediately but the 220 response of client
   should retry later if possible (if, for example, another client is in
   the
     ARTICLE command.
  9.2.3.2  Examples

     Example of a successful retrieval process of sending the body of an article
     (using no same article number)
          [S] 200 NNTP Service Ready
          [C] GROUP misc.test
          [S] 211 1234 3000234 3002322 misc.test
          [C] BODY
          [S] 222 3000234 <45223423@example.com>
          [S] This is just a test article.
          [S] .
     Example of to the server), a successful retrieval 436
   response MUST be returned.

   If transmission of the body of an article
     by message-id
          [S] 200 NNTP Service Ready
          [C] BODY <45223423@example.com>
          [S] 222 0 <45223423@example.com>
          [S] This is just a test article.
          [S] .
     Example of an unsuccessful retrieval of requested, the body of an
     article by message-id
          [S] 200 NNTP Service Ready
          [C] BODY <i.am.not.there@example.com>
          [S] 430 No Such Article Found
     Example of an unsuccessful retrieval of client MUST send the body of an
     article by number
          [S] 200 NNTP Service Ready
          [C] GROUP misc.test
          [S] 211 1234 3000234 3002322 misc.test
          [C] BODY 300256
          [S] 423 No such article number
   entire article, including header and body, in this group
     Example of an unsuccessful retrieval of the body of an
     article by number because format defined
   above (Section 3) for multi-line responses (except that there is no newsgroup was selected first
          [S] 200 NNTP Service Ready
          [C] BODY 300256
          [S] 412 No newsgroup selected

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     Example of an attempt to retrieve
   initial line containing a response code).  Thus a single dot (".") on
   a line indicates the body end of an article when the current group selected is empty
          [S] 200 NNTP Service Ready
          [C] GROUP example.empty.newsgroup
          [S] 211 0 0 0 example.empty.newsgroup
          [C] BODY
          [S] 420 No current article selected
     Example of text, and lines starting with a failure due to dot
   in the service being unavailable
          [S] 200 NNTP Service Ready
          [C] BODY <i.am.a.test.article@example.com>
          [S] 502 Service unavailable

  9.2.4  STAT

     STAT <message-id>
     STAT [number] original text have that dot doubled during transmission.  The STAT command behaves identically to
   server MUST return either a 235 response, indicating that the ARTICLE command
     except that, if article
   was successfully transferred, a 436 response, indicating that the
   transfer failed but should be tried again later, or a 437 response,
   indicating that the article exists, was rejected.

   This function differs from the POST command in that it is intended
   for use in transferring already-posted articles between hosts.  It
   SHOULD NOT presented to be used when the client.

     This client is a personal news reading
   program, since this command allows indicates that the client to determine whether an forthcoming article exists,
   has already been posted at another site and in is being forwarded from
   another host.  However, the second form what its message-id
     is, without having to process an arbitrary amount of text.
  9.2.4.1  Responses

     First form (message-id specified):

            223 0 a  Article exists (a = message-id)
            430      No article found with that message-id
            502      Program error, function server MAY elect not performed

     Second form (optional to post or forward
   the article number specified):

            223 n a  Article exists (n = if after further examination of the article number, a =
                     message-id)
            412      No newsgroup selected
            420      No current it deems it
   inappropriate to do so.  Reasons for such subsequent rejection of an
   article selected
            423      No may include such problems as inappropriate newsgroups or
   distributions, disc space limitations, article in this newsgroup
            502      Program error, function not performed

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     The parameters of lengths, garbled
   headers, and the 223 response like.  These are identical to those typically restrictions enforced by
   the server host's news software and not necessarily the NNTP server
   itself.

   The client SHOULD NOT assume that would have the article has been given in a 220 successfully
   transferred unless it receives an affirmative response to the
     equivalent ARTICLE command. However, from the
   server.  A lack of response (such as a dropped network connection or
   a network timeout) SHOULD be treated the same as a 436 response.

   Because some news server software may not be able immediately to
   determine whether or not an article is NOT
     multi-line.
  9.2.4.2 suitable for posting or
   forwarding, an NNTP server MAY acknowledge the successful transfer of
   the article (with a 235 response) but later silently discard it.

7.3.2.3 Examples

   Example of STAT on successfully sending an existing article (using no article
     number)
          [S] 200 NNTP Service Ready to another site:

      [C] GROUP misc.test IHAVE <i.am.an.article.you.will.want@example.com>
      [S] 211 1234 3000234 3002322 335 Send it; end with <CR-LF>.<CR-LF>
      [C] Path: pathost!demo!somewhere!not-for-mail
      [C] From: "Demo User" <nobody@example.com>
      [C] Newsgroups: misc.test
      [C] STAT
          [S] 223 3000234 <45223423@example.com>
     Example of Subject: I am just a STAT of an existing test article by message-id
          [S] 200 NNTP Service Ready
      [C] STAT <45223423@example.com>
          [S] 223 0 <45223423@example.com> Date: 6 Oct 1998 04:38:40 -0500
      [C] Organization: An Example of an STAT of an article not on the server by
     message-id
          [S] 200 NNTP Service Ready Com, San Jose, CA
      [C] STAT <i.am.not.there@example.com> Message-ID: <i.am.a.test.article@example.com>
      [C]
      [C] This is just a test article.
      [C] .
      [S] 430 No Such 235 Article Found transferred OK

   Example of STAT of sending an article not in the server by number
          [S] 200 NNTP Service Ready to another site that rejects it:

      [C] GROUP misc.test IHAVE <i.am.an.article.you.will.want@example.com>
      [S] 211 1234 3000234 3002322 335 Send it; end with <CR-LF>.<CR-LF>
      [C] Path: pathost!demo!somewhere!not-for-mail
      [C] From: "Demo User" <nobody@example.com>
      [C] Newsgroups: misc.test
      [C] STAT 300256
          [S] 423 No such Subject: I am just a test article number in this group
      [C] Date: 6 Oct 1998 04:38:40 -0500
      [C] Organization: An Example of STAT of an article by number when no newsgroup was
     selected first
          [S] 200 NNTP Service Ready Com, San Jose, CA
      [C] STAT 300256 Message-ID: <i.am.a.test.article@example.com>
      [C]
      [C] This is just a test article.
      [C] .
      [S] 412 No newsgroup selected 437 Article rejected; don't send again
   Example of STAT of sending an article when to another site where the current group selected
     is empty
          [S] 200 NNTP Service Ready transfer
   fails:

      [C] GROUP example.empty.newsgroup IHAVE <i.am.an.article.you.will.want@example.com>
      [S] 211 0 0 0 example.empty.newsgroup 335 Send it; end with <CR-LF>.<CR-LF>
      [C] STAT
          [S] 420 No current Path: pathost!demo!somewhere!not-for-mail
      [C] From: "Demo User" <nobody@example.com>
      [C] Newsgroups: misc.test
      [C] Subject: I am just a test article selected
      [C] Date: 6 Oct 1998 04:38:40 -0500
      [C] Organization: An Example of a failure due to the service being unavailable

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          [S] 200 NNTP Service Ready Com, San Jose, CA
      [C] STAT Message-ID: <i.am.a.test.article@example.com>
          [S] 502 Service unavailable

  9.3  Article Posting

     Article posting is done in one of two modes: individual
     article posting from news reading clients and article
     transfer from other news servers.

  9.3.1  POST

     POST
     If posting
      [C]
      [C] This is allowed, response code 340 MUST be returned just a test article.
      [C] .
      [S] 436 Transfer failed

   Example of sending an article to
     indicate a site that the already has it:

      [C] IHAVE <i.am.an.article.you.have@example.com>
      [S] 435 Duplicate

   Example of sending an article to be posted should be sent.
     Response code 440 MUST be sent if a site that posting is prohibited
     for some installation-dependent reason.

     If posting is permitted, requests the article MUST be presented to the
     server by the client in the format specified by RFC 1036 (or
     by
   tried again later:

      [C] IHAVE <i.am.an.article.you.defer@example.com>
      [S] 436 Retry later

8. Information commands

   This section lists other commands that may be used at any of its successors or extensions). The text forming time
   between the
     header and body beginning of the message to be posted MUST be sent by
     the client in the format defined above (section 0) for multi-
     line responses (except that there is no initial line
     containing a response code).  Thus a single period (".") on a
     line indicates the end of the text, session and lines starting with a
     period in the original text have that period doubled during
     transmission.

     Following the presentation of the termination sequence by the
     client, the server MUST return a response code indicating
     success or failure of its termination.  Using these
   commands does not alter any state information, but the article transfer. Note that response codes 340
   generated from their use may provide useful information to clients.

   All servers MUST implement these commands.

8.1 DATE

8.1.1 Usage

   Syntax
      DATE

   Responses
      111 yyyymmddhhmmss   server date and 440 are used in direct response time

   Parameters
      yyyymmddHHmmss = Current UTC date and time on server

8.1.2 Description

   This command exists to help clients find out the
     POST command. Others are returned following the sending of current Coordinated
   Universal Time [9] from the article.

     No attempt shall server's perspective.  This command MUST
   NOT be made by the server used as a substitute for NTP [10], but to filter characters,
     fold or limit lines, or otherwise process incoming text. The
     intent is provide information
   that the server just passes the incoming message to might be posted to useful when using the server installation's news posting software,
     which is not defined by this memo.

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     The client NEWNEWS command (see Section
   8.4).  A system providing NNTP service SHOULD NOT assume that the article has been
     successfully transferred unless it receives an affirmative
     response from implement NTP for the server.  Since, however,
   purposes of keeping the affirmative system clock as accurate as possible.

   The server MUST return a 111 response may have been sent and lost, specifying the client SHOULD use date and time on
   the same message-id server in the article when resending it or check
     whether the article was successfully posted before resending
     it to ensure that the resend will not result in a duplicate
     article. form yyyymmddhhmmss.  This command date and time is not streamable.
  9.3.1.1  Responses

            240 Article received ok
            340 Send article to be posted
            440 Posting not permitted
            441 Posting failed

  9.3.1.2 in
   Coordinated Universal Time.

8.1.3 Examples

     Example of a successful posting
          [S] 200 NNTP Service Ready

      [C] POST DATE
      [S] 340 Input article. End with <CR-LF>.<CR-LF>
          [C] From: ˘Demo User÷ <nobody@example.net>
          [C] Newsgroups: misc.test
          [C] Subject: I am just 111 19990623135624

8.2 HELP

8.2.1 Usage
   Syntax
      HELP

   Responses
      100   Help text follows (multiline)

8.2.2 Description

   This command provides a short summary of commands that are understood
   by this implementation of the server.  The help text will be
   presented as a test article
          [C] Organization: An Example Net
          [C]
          [C] multiline response following the 100 response code.

   This text is just not guaranteed to be in any particular format and MUST
   NOT be used by clients as a test article. replacement for the LIST EXTENSIONS
   command described in Section 6.1

8.2.3 Examples

      [C] .
          [S] 240 Article received ok
     Example of an unsuccessful posting HELP
      [S] 200 NNTP Service Ready
          [C] POST 100 Help text follows
      [S] 340 Input article. End with <CR-LF>.<CR-LF>
          [C] From: ˘Demo User÷ <nobody@example.net>
          [C] Newsgroups: misc.test
          [C] Subject: I am just a test article
          [C] Organization: An Example Net
          [C]

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          [C] This is just a test article.
          [C] . some help text.  There is no specific
      [S] 441 Posting failed
     Example of an attempt to post when posting formatting requirement for this test, though
      [S] it is not allowed customary for it to list the valid commands
      [S] 201 NNTP Service Ready, read-only
          [C] POST and give a brief definition of what they do
      [S] 440 Posting not permitted

  9.3.2  IHAVE

     IHAVE <message-id> .

8.3 NEWGROUPS

8.3.1 Usage

   Syntax
      NEWGROUPS date time [GMT]

   Responses
      231   List of new newsgroups follows (multiline)

   Parameters
      date = Date in yymmdd or yyyymmdd format
      time = Time in hhmmss format

8.3.2 Description

   This command returns a list of newsgroups created on the server since
   the specified date and time.  The IHAVE results are in the same format as
   the LIST ACTIVE command informs (see Section 8.6.1).

   OUTSTANDING ISSUE

      Does the output include high/low/status or not? If so, the
      examples are wrong.  If not, the above text is wrong.

   The date is specified as 6 or 8 digits in the server that format [xx]yymmdd,
   where xx is the client has an
     article whose id first two digits of the year (19-99), yy is <message-id>.  If the server desires a
     copy last
   two digits of that article, it MUST return response code 335
     instructing the client to send year (00-99), mm is the entire article.  If month (01-12), and dd is
   the
     server does not want day of the article (if, for example, month (01-31).  If the server
     already has a copy first two digits of it), response code 435 indicating that the article is year
   are not wanted MUST be returned.  Finally, if specified, the
     article isn't wanted immediately but year is to be taken from the client should retry
     later current century
   if possible (if, for example, another client yy is in the
     process of sending the same article smaller than or equal to the server), response
     code 436 MUST be returned.

     If transmission of current year, otherwise the article
   year is requested, the client MUST
     send from the entire article, including header and body, previous century.

   The time is specified as 6 digits in the format defined above (section 4) for multi-line responses
     (except that there hhmmss, where hh is no initial line containing a response
     code). Thus a single period (".") on a line indicates the end
     of
   the text, and lines starting with a period hours in the original
     text have that period doubled during transmission. The server
     MUST return either response code 235, indicating that 24-hour clock (00-23), mm is the
     article was successfully transferred, response code 436,
     indicating that minutes (00-59),
   and ss is the transfer failed but should be tried again
     later, or response code 437, indicating seconds (00-60, to allow for leap seconds).  The token
   "GMT" specifies that the article was
     rejected.

     This function differs from date and time are given in Coordinated
   Universal Time; if it is omitted then the POST command date and time are specified
   in the server's local timezone.  Note that it there is
     intended for use no way using the
   protocol specified in transferring already-posted articles
     between hosts. It SHOULD NOT be used when this document to establish the client server's local
   timezone.

   Note that an empty list is a
     personal news reading program, since this command possible valid response and indicates
   that there are no new newsgroups since that date-time.

   Clients SHOULD make all queries using Coordinated Universal Time
   (i.e.  by including the forthcoming article has already been "GMT" parameter) when possible.

8.3.3 Examples

   Example where there are new groups:

      [C] NEWGROUPS 19990624 000000 GMT
      [S] 231 list of new newsgroups follows
      [S] alt.rfc-writers.recovery
      [S] tx.natives.recovery
      [S] .

   Example where there are no new groups:

      [C] NEWGROUPS 19990624 000000 GMT
      [S] 231 list of new newsgroups follows
      [S] .

8.4 NEWNEWS

8.4.1 Usage

   Syntax
      NEWNEWS wildmat date time [GMT]

   Responses
      230   List of new articles follows (multiline)

   Parameters
      wildmat = Newsgroups of interest
      date    = Date in yymmdd or yyyymmdd format
      time    = Time in hhmmss format

8.4.2 Description

   This command returns a list of message-ids of articles posted at
     another site and is being forwarded from another host.

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     However, the server MAY elect not to post or forward
   received on the
     article if after further examination of server, in the article it deems
     it inappropriate to do so. Reasons for such subsequent
     rejection of an article may include such problems as
     inappropriate newsgroups or distributions, disk space
     limitations, article lengths, garbled headers, and whose names match the like.
     These are typically restrictions enforced by
   wildmat, since the server
     host's news software specified date and not necessarily time.  One message-id is sent
   on each line; the NNTP server
     itself.

     The client SHOULD NOT assume that order of the article has been
     successfully transferred unless it receives an affirmative response has no specific significance
   and may vary from response to response in the server. same session.  A lack of response (such
   message-id MAY appear more than once; if it does so, it has the same
   meaning as a
     dropped network connection or a network timeout) SHOULD be
     treated if it appeared only once.

   Date and time are in the same format as a 436 error response.

     Because some news server software may not be able immediately
     to determine whether or not the NEWGROUPS command (see
   Section 8.3).

   Note that an article empty list is suitable for
     posting or forwarding, an NNTP server MAY acknowledge a possible valid response and indicates
   that there is currently no new news in the
     successful transfer of relevant groups.

   Clients SHOULD make all queries in Coordinated Universal Time (i.e.
   by using the article (with a 235 response) but
     later silently discard it.
  9.3.2.1  Responses

            235 Article transferred ok
            335 Send article to be transferred
            435 Article not wanted, please donĂt send it.
            436 Transfer failed, try again later.
            437 Article rejected, please donĂt sent it again.

  9.3.2.2  Examples

     Example of successfully sending an article to another site
          [S] 200 NNTP Service Ready
          [C] IHAVE <i.am.an.article.you.will.want@example.com>
          [S] 335 Send it. End with <CR-LF>.<CR-LF>
          [C] Path: pathost!demo!somewhere!not-for-mail
          [C] From: ˘Demo User÷ <nobody@example.com>
          [C] Newsgroups: misc.test
          [C] Subject: I am just a test article
          [C] Date: 6 Oct 1998 04:38:40 -0500

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          [C] Organization: An "GMT" parameter) when possible.

8.4.3 Examples

   Example Com, San Jose, CA
          [C] Message-ID: <i.am.a.test.article@example.com>
          [C]
          [C] This is just a test article. where there are new articles:

      [C] . NEWNEWS news.*,sci.* 19990624 000000 GMT
      [S] 235 Article transferred ok
     Example 230 list of sending an article to another site that rejects it new articles by message-id follows
      [S] 200 NNTP Service Ready
          [C] IHAVE <i.am.an.article.you.will.want@example.com> <i.am.a.new.article@example.com>
      [S] 335 Send it. End with <CR-LF>.<CR-LF>
          [C] Path: pathost!demo!somewhere!not-for-mail
          [C] From: ˘Demo User÷ <nobody@example.com>
          [C] Newsgroups: misc.test
          [C] Subject: I am just a test article
          [C] Date: 6 Oct 1998 04:38:40 -0500
          [C] Organization: An <i.am.another.new.article@example.com>
      [S] .

   Example Com, San Jose, CA
          [C] Message-ID: <i.am.a.test.article@example.com>
          [C]
          [C] This is just a test article. where there are no new articles:

      [C] . NEWNEWS alt.* 19990624 000000 GMT
      [S] 437 Article rejected. Don't send again
     Example 230 list of sending an new articles by message-id follows
      [S] .

8.5 Time

   As described in Section 7, each article to another site where has an arrival timestamp.
   Each newsgroup also has a creation timestamp.  These timestamps are
   used by the
     transfer fails
          [S] 200 NNTP Service Ready
          [C] IHAVE <i.am.an.article.you.will.want@example.com>
          [S] 335 Send it. End with <CR-LF>.<CR-LF>
          [C] Path: pathost!demo!somewhere!not-for-mail
          [C] From: ˘Demo User÷ <nobody@example.com>
          [C] Newsgroups: misc.test
          [C] Subject: I am just NEWNEWS and NEWGROUP commands to construct their
   reponses.

   The DATE command MUST return a test timestamp from the same clock as is
   used for determining article
          [C] Date: 6 Oct 1998 04:38:40 -0500
          [C] Organization: An Example Com, San Jose, CA
          [C] Message-ID: <i.am.a.test.article@example.com>
          [C]
          [C] arrival and group creation times.  This is just a test article.
          [C] .
          [S] 436 Transfer failed
     Example
   clock SHOULD be monotonic, and adjustments SHOULD be made by running
   it fast or slow compared to "real" time rather than by making sudden
   jumps.

   Clients can ensure that they do not have gaps in lists of sending an article to articles or
   groups by using the DATE command in the following manner:

   First session:
      Issue DATE command and record result
      Issue NEWNEWS command using a site previously chosen timestamp

   Subsequent sessions:
      Issue DATE command and hold result in temporary storage
      Issue NEWNEWS command using timestamp saved from previous session
      Overwrite saved timestamp with that already has currently in temporary storage

   In order to allow for minor errors, clients MAY want to adjust the
   timestamp back by two or three minutes before using it in NEWNEWS.

8.5.1 Examples

   First session:

      [C] DATE
      [S] 200 NNTP Service Ready 111 20010203112233
      [C] IHAVE <i.am.an.article.you.have@example.com> NEWNEWS local.chat 20001231 235959 GMT
      [S] 435 Duplicate

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     Example of sending an article to a site that requests 230 list follows
      [S] <article.1@local.service>
      [S] <article.2@local.service>
      [S] <article.3@local.service>
      [S] .

   Second session (the client has subtracted 3 minutes from the
     article be tried again later
   timestamp returned previously):

      [C] DATE
      [S] 200 NNTP Service Ready 111 20010204003344
      [C] IHAVE <i.am.an.article.you.defer@example.com> NEWNEWS local.chat 20010203 111933 GMT
      [S] 436 Retry later

  9.4 230 list follows
      [S] <article.3@local.service>
      [S] <article.4@local.service>
      [S] <article.5@local.service>
      [S] .

   Note how <article.3@local.service> arrived in the 3 minute gap and so
   is listed in both responses.

8.6 The LIST Keyword

  9.4.1 commands

8.6.1 LIST ACTIVE

8.6.1.1 Usage

   Syntax
      LIST [ACTIVE [wildmat]] ACTIVE [wildmat]

   Responses
      215   Information follows (multiline)

   Parameters
      wildmat = groups of interest

8.6.1.2 Description

   The response to the LIST keyword ACTIVE command with no parameters returns a list of valid
   newsgroups and associated information.  Each newsgroup is sent as a
   line of text in the following format:

   group first last status
     where <group>

   where:

   "group" is the name of the newsgroup, <last> newsgroup;

   "first" is the
     number of current low water mark for the last known article currently in that newsgroup,
     <first> group;

   "last" is the number of the first article currently in current high water mark for the
     newsgroup, and <status> indicates group;

   "status" is the current status of the group on this server. Typically, the <status> will consist of
     the US-ASCII character 'y' where server; typically
      this is one of:

      "y" posting is permitted, 'n'
     where permitted

      "n" posting is not permitted and 'm' where
      "m" postings will be forwarded to the newsgroup moderator by the news server.

      Other status strings may exist.  The definition of these other
      values and the circumstances under which they are returned is
     covered in other specifications. are returned is
      covered in other specifications.

      OUTSTANDING ISSUE

         Is the order "group first last status" or "group last first
         status"? The examples match the description above, but they
         don't match the news server I have tested.

   Each field in the line is separated from its neighboring fields by
   one or more US-ASCII spaces.

   The <first> "first" and <last> "last" fields will always be numeric.  They
     may have leading zeros. The <first> field corresponds to the
     "reported low water mark" and the <last> field corresponds correspond to the "reported high and low water mark"
   marks described in the GROUP command (see Section 9.1.1.1). 7.1.1).

   The status of a newsgroup only indicates how posts to that newsgroup
   are processed.  It does not indicate if the current client is
   permitted to post.  That is indicated by the status
     code returned as part of the greeting.
     Please note that an empty list (i.e., the text body returned
     by this command consists only of the terminating period) is a

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     possible valid response, and indicates that there are
     currently no valid newsgroups.

     If the optional wildmat parameter is specified, the list is
     limited to only the groups that match the pattern.
  9.4.1.1  Responses
            215 Information Follows (multi-line response)

  9.4.1.2  Examples

     Example of LIST returning a list of newsgroups
          [S] 200 NNTP Service Ready
          [C] LIST
          [S] 215 list of newsgroups follows
          [S] misc.test 3000234 3002322 y
          [S] alt.fc-writers.recovery 1 4 y
          [S] tx.natives.recovery 56 89 y
          [S] .
     Example of LIST returning no newsgroups
          [S] 200 NNTP Service Ready
          [C] LIST
          [S] 215 list of newsgroups follows
          [S] .

  9.4.2  LIST ACTIVE.TIMES

     LIST ACTIVE.TIMES [wildmat]
     The active.times file is maintained by some news transport
     systems to contain information about who created a particular
     newsgroup and when. The format of this file includes three
     fields separated from each other by one or more US-ASCII
     space characters. The first field is the name of the
     newsgroup. The second is the time when this group was created
     on this news server measured in seconds since the start of
     January 1, 1970.  The third is indicated by the email address status code returned as
   part of the
     entity greeting.  Note that created the newsgroup and must be a mailbox as
     defined in RFC 28228. When executed, the information is
     displayed following the 215 response. When display an empty list is
     completed, the server will send a period on a line by itself.
     If the information is not available, the server will return

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     the 503 error response. If the server does not recognize the
     command, it SHOULD return the 501 error response. possible valid
   response, and indicates that there are currently no valid newsgroups.

   If the optional wildmat parameter is specified, the list is limited
   to only the groups that whose names match the pattern.
  9.4.2.1  Responses

            215 Information Follows (multi-line response)
            501 Syntax error
            503 Program error, function not performed
  9.4.2.2 wildmat.  If no wildmat is
   specified, the keyword ACTIVE MAY be omitted without altering the
   effect of the command.

8.6.1.3 Examples

   Example of LIST ACTIVE.TIMES ACTIVE returning a list of newsgroups
          [S] 200 NNTP Service Ready newsgroups:

      [C] LIST ACTIVE.TIMES ACTIVE
      [S] 215 information list of newsgroups follows
      [S] misc.test 930445408 <creatme@isc.org> 3000234 3002322 y
      [S] alt.rfc-writers.recovery 930562309 <m@example.com> alt.fc-writers.recovery 1 4 y
      [S] tx.natives.recovery 930678923 <sob@academ.com> 56 89 y
      [S] .

   Example of LIST ACTIVE.TIMES returning an error (The server
     software is not configured to maintain this information, but
     does recognize ACTIVE omitting the command as valid.)
          [S] 200 NNTP Service Ready second keyword and returning no
   newsgroups:

      [C] LIST ACTIVE.TIMES
      [S] 503 program error, function not performed 215 list of newsgroups follows
      [S] .

   Example of LIST ACTIVE.TIMES sent to ACTIVE with a server that does not
     recognize this argument (e.g. The software does not maintain
     this information.)
          [S] 200 NNTP Service Ready wildmat:

      [C] LIST ACTIVE.TIMES ACTIVE *.recovery
      [S] 501 Syntax Error

  9.4.3 215 list of newsgroups follows
      [S] alt.fc-writers.recovery 1 4 y
      [S] tx.natives.recovery 56 89 y
      [S] .

8.6.2 LIST DISTRIBUTIONS ACTIVE.TIMES

8.6.2.1 Usage

   This command is optional.

   Syntax
      LIST DISTRIBUTIONS ACTIVE.TIMES [wildmat]

   Responses
      215   Information follows (multiline)
      503   Facility not available

   Parameters
      wildmat = groups of interest

8.6.2.2 Description

   The distributions active.times file is maintained by some news transport systems to
   contain information about valid values for the
     Distribution: line in who created a news article header particular newsgroup and about what
     the values mean.
   when.  Each line contains two fields, the value and

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     a short explanation on the meaning of the value. The first
     field is this file consists of three fields separated from the second field
   each other by one or more US-
     ASCII spaces. When executed, the information US-ASCII space characters.  The first field
   is displayed
     following the 215 response. When display name of the newsgroup.  The second is completed, the
     server will send a period time when this group
   was created on this news server, measured in seconds since the start
   of January 1, 1970.  The third is the email address of the entity
   that created the newsgroup, and must be a line by itself. mailbox as defined in RFC
   2822 [7].

   If the information is not available, it is returned as a multi-line
   response following the server will return 215 response code.  If the information is not
   available, a 503
     error response. response MUST be returned.  If the server does not
   recognize this
     command, it SHOULD return the command, a 501 error response.
  9.4.3.1  Responses

            215 Information Follows (multi-line response)
            501 Syntax error
            503 Program error, function not performed

  9.4.3.2 response MUST be returned.

   If the optional wildmat parameter is specified, the list is limited
   to only the groups whose names match the wildmat (and therefore may
   be empty).

8.6.2.3 Examples

   Example of LIST DISTRIBUTIONS ACTIVE.TIMES returning a list of newsgroups
          [S] 200 NNTP Service Ready newsgroups:

      [C] LIST DISTRIBUTIONS ACTIVE.TIMES
      [S] 215 information follows
      [S] usa United States of America misc.test 930445408 <creatme@isc.org>
      [S] na North America alt.rfc-writers.recovery 930562309 <m@example.com>
      [S] world All over the World tx.natives.recovery 930678923 <sob@academ.com>
      [S] .

   Example of LIST DISTRIBUTIONS ACTIVE.TIMES returning an error (e.g. The
     server software where the command is
   recognised but the software does not configured to maintain this
     information, but does recognize the command as valid.)
          [S] 200 NNTP Service Ready information:

      [C] LIST DISTRIBUTIONS ACTIVE.TIMES
      [S] 503 program error, function not performed

   Example of LIST DISTRIBUTIONS ACTIVE.TIMES sent to a server that does not recognize the command (e.g. The server does not maintain
   this
     information regardless of configuration.)
          [S] 200 NNTP Service Ready command:

      [C] LIST DISTRIBUTIONS ACTIVE.TIMES
      [S] 501 Syntax Error

  9.4.4

8.6.3 LIST DISTRIB.PATS DISTRIBUTIONS

8.6.3.1 Usage

   This command is optional.

   Syntax
      LIST DISTRIB.PATS

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   Responses
      215   Information follows (multiline)
      503   Facility not available

8.6.3.2 Description

   The distrib.pats distributions file is maintained by some news transport systems
   to allow clients to choose a value contain information about valid values for the Distribution: line
   in the header of a news article being
     posted. The information returned consists header and about what the values mean.  Each line
   of lines, in no
     particular order, each this file consists of which contains three two fields separated from each other by colons. These fields are a weight, a wildmat
     (which may be a simple group name), and a Distribution:
     value, in that order. one
   or more US-ASCII space characters.  The client MAY use this information to select first field is a Distribution: value based on the name of a newsgroup. To do so, it should
     determine and
   the lines whose second field matches the newsgroup
     name, select that line with the highest weight (with 0 being
     the lowest), and use is a short explanation of the Distribution: field from meaning of that line.
     When executed, value.

   If the information is displayed available, it is returned as a multi-line
   response following the 215
     response.  When display is completed, the server will send a
     period on a line by itself. response code.  If the information is not
   available, the server will return the a 503 error response. response MUST be returned.  If
     this command is not recognized, the server SHOULD return the
     501 error response.
  9.4.4.1  Responses

            215 Information Follows (multi-line response)
            501 Syntax error
            503 Program error, function does not performed

  9.4.4.2
   recognize the command, a 501 response MUST be returned.

8.6.3.3 Examples

   Example of LIST DISTRIB.PATS DISTRIBUTIONS returning a list of newsgroups
          [S] 200 NNTP Service Ready distributions:

      [C] LIST DISTRIB.PATS DISTRIBUTIONS
      [S] 215 information follows
      [S] 10:local.*:local usa United States of America
      [S] na North America
      [S] world All over the World
      [S] .

   Example of LIST DISTRIB.PATS DISTRIBUTIONS returning an error (e.g. The
     server software where the command is
   recognised but the software does not configured to maintain this
     information, but does recognize the command as valid.)
          [S] 200 NNTP Service Ready information:

      [C] LIST DISTRIB.PATS DISTRIBUTIONS
      [S] 503 program error, function not performed

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   Example of LIST DISTRIB.PATS DISTRIBUTIONS sent to a server that does not
   recognize the command (e.g. The software does not maintain this information regardless of configuration.)
          [S] 200 NNTP Service Ready command:

      [C] LIST DISTRIB.PATS DISTRIBUTIONS
      [S] 501 Syntax Error

  9.4.5

8.6.4 LIST NEWSGROUPS DISTRIB.PATS

8.6.4.1 Usage

   This command is optional.

   Syntax
      LIST NEWSGROUPS [wildmat] DISTRIB.PATS

   Responses
      215   Information follows (multiline)
      503   Facility not available

8.6.4.2 Description

   The newsgroups distrib.pats file is maintained by some news transport systems to contain
   choose a value for the name Distribution: line in the header of a news
   article being posted.  Each line of this file consists of three
   fields separated from each newsgroup that other by a US-ASCII colon.  The first
   field is active
     on a weight, the server second field is a wildmat (which may be a
   simple group name), and the third field is a short description about value for the purpose
   Distribution: header.

   The client MAY use this information to select a Distribution: value
   based on the name of
     each a newsgroup. Each line in  To do so, it should determine the file contains two fields,
   lines whose second field matches the newsgroup name name, select from
   among them the line with the highest weight (with 0 being the
   lowest), and a short explanation of use the purpose value of
     that newsgroup. The first field is separated from the second third field by one or more US-ASCII spaces. When executed, to construct the
   Distribution: header.

   If the information is displayed available, it is returned as a multi-line
   response following the 215 response. When
     display is completed, the server will send a period on a line
     by itself. response code.  If the information is not
   available, the server
     will return the a 503 response. response MUST be returned.  If the server does not
   recognize the command it should return command, a 501 response. If the
     optional wildmat parameter is specified, the list is limited
     to only those groups that match the wildmat (no matching is
     done on the group descriptions). If nothing is matched an
     empty list is returned, not an error.
  9.4.5.1  Responses

            215 Information Follows (multi-line response)
            501 Syntax error
            503 Program error, function not performed

  9.4.5.2 response MUST be returned.

8.6.4.3 Examples

   Example of LIST NEWSGROUPS DISTRIB.PATS returning a list of newsgroups
          [S] 200 NNTP Service Ready newsgroups:

      [C] LIST NEWSGROUPS DISTRIB.PATS
      [S] 215 information follows
      [S] misc.test General Usenet testing 10:local.*:local
      [S] alt.rfc-writers.recovery RFC Writers Recovery

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      [S] tx.natives.recovery Texas Natives Recovery 20:local.here.*:thissite
      [S] .

   Example of LIST NEWSGROUPS DISTRIB.PATS returning an error (e.g. The
     server software recognizes where the command as valid, is
   recognised but the
     information is software does not available.)
          [S] 200 NNTP Service Ready maintain this information:

      [C] LIST NEWSGROUPS DISTRIB.PATS
      [S] 503 program error, function not performed

  9.5  Standard extensions

     Each

   Example of the following sections describes an extension that LIST DISTRIB.PATS sent to a server MAY provide. If the server provides the extension, it
     MUST include the appropriate extension label in the response
     to LIST EXTENSIONS. If it that does not provide it, it MUST NOT
     include the appropriate extension label. The descriptions of
     facilities in each section are written as if the extension is
     provided. If it is not provided, the entire section should be
     ignored.

  9.5.1  LISTGROUP extension

     This extension provides one command and has the extension
     label LISTGROUP.
  9.5.1.1  The LISTGROUP Command

     LISTGROUP [ggg]
     The LISTGROUP command is used to get a listing recognize
   this command:

      [C] LIST DISTRIB.PATS
      [S] 501 Syntax Error

8.6.5 LIST NEWSGROUPS

8.6.5.1 Usage

   This command is optional.

   Syntax
      LIST NEWSGROUPS [wildmat]

   Responses
      215   Information follows (multiline)
      503   Facility not available
   Parameters
      wildmat = groups of all the
     article numbers in a particular newsgroup. interest

8.6.5.2 Description

   The optional parameter ggg newsgroups file is maintained by some news transport systems to
   contain the name of the each newsgroup to be
     selected (e.g. "news.software.misc").  A list of valid
     newsgroups may be obtained from the LIST command. If no group
     is specified, the current group that is used as available on the default
     argument.

     The successful selection response will be server
   and a list of the
     article numbers in short description about the group followed by a period on a line
     by itself. The list starts on purpose of the next group.  Each line following the 211
     response code.

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     When a valid group is selected by means of
   this command, the
     internally maintained "current article pointer" MUST be set
     to the file consists of two fields separated from each other by one or
   more US-ASCII space characters.  The first article in the group and field is the name of the current
   newsgroup MUST be set to and the selected newsgroup name. If an
     invalid group second is specified, a short description of the previously selected group and
     article remain selected.  If group.  Note
   that an empty newsgroup list is selected,
     the "current article pointer" may be in an indeterminate
     state and should not be used.

     The LISTGROUP keyword MAY be used by a client as a
     replacement for the GROUP command in establishing a possible valid
     "current article pointer." After a successful response is
     received, any other command may be used response, and indicates that depends on
     having the "current article pointer" be valid.
   there are currently no valid newsgroups.

   If a group name the information is specified and that group available, it is not available
     on that server, returned as a multi-line
   response following the server 215 response code.  If the information is not
   available, a 503 response MUST respond with be returned.  If the 411 error
     code.

     A server that does not implement this command SHOULD return
   recognize the command, a
     500 error response.
  9.5.1.1.1  Responses

            211 List of article numbers follow (multi-line
                response)
            411 No such group
            412 No newsgroup currently selected
            500 Command not recognized

  9.5.1.1.2 501 response MUST be returned.

   If the optional wildmat parameter is specified, the list is limited
   to only the groups whose names match the wildmat.

8.6.5.3 Examples

   Example of LISTGROUP on an empty group:
          [S] 200 NNTP Service Ready
          [C] LISTGROUP example.empty.newsgroup
          [S] 211 LIST NEWSGROUPS returning a list of article numbers follows
          [S] .
     Example of LISTGROUP on a valid current group:
          [S] 200 NNTP Service Ready
          [C] GROUP misc.test
          [S] 211 2000 3000234 3002322 misc.test selected

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      [C] LISTGROUP LIST NEWSGROUPS
      [S] 211 list 215 information follows
      [S] 3000234
          [S] 3000237
          [S] 3000238 misc.test General Usenet testing
      [S] 3000239 alt.rfc-writers.recovery RFC Writers Recovery
      [S] 3002322 tx.natives.recovery Texas Natives Recovery
      [S] .

   Example of LISTGROUP failing because no group LIST NEWSGROUPS returning an error where the command is
   recognised but the software does not maintain this information:

      [C] LIST NEWSGROUPS
      [S] 503 program error, function not performed

   Example of LIST NEWSGROUPS sent to a server that does not recognize
   this command:

      [C] LIST NEWSGROUPS
      [S] 501 Syntax error

9. The CONCLUSION step

9.1 QUIT

9.1.1 Usage

   Syntax
      QUIT

   Responses
      205   Connection closing

9.1.2 Description

   The server process MUST acknowledge the QUIT command and then close
   the connection to the client.  This is the preferred method for a
   client to indicate that it has been
     selected:
          [S] 200 finished all its transactions with the
   NNTP Service Ready
          [C] LISTGROUP
          [S] 412 no current group
          [C] GROUP example.is.sob.bradner.or.barber
          [S] 411 no such group server.

   If a client simply disconnects (or the connection times out or some
   other fault occurs), the server MUST gracefully cease its attempts to
   service the client, disconnecting from its end if necessary.

9.1.3 Examples

      [C] LISTGROUP QUIT
      [S] 412 no current group

  9.5.2  The OVER Extension 205 closing connection
      [Server closes connection.]

10. Framework for NNTP extensions

   Although NNTP is widely and robustly deployed, some parts of the
   Internet community might wish to extend the NNTP service.  This
   document defines a means whereby an extended NNTP client can query
   the server to determine the service extensions that it supports.

   It must be emphasized that any extension provides two commands, OVER to the NNTP service should
   not be considered lightly.  NNTP's strength comes primarily from its
   simplicity.  Experience with many protocols has shown that:

      Protocols with few options tend towards ubiquity, whilst protocols
      with many options tend towards obscurity.

   This means that each and LIST
  OVERVIEW.FMT. The label every extension, regardless of its benefits,
   must be carefully scrutinized with respect to its implementation,
   deployment, and interoperability costs.  In many cases, the cost of
   extending the NNTP service will likely outweigh the benefit.

   Given this environment, the framework for extensions described in
   this extension is OVER.
  9.5.2.1  LIST OVERVIEW.FMT

     LIST OVERVIEW.FMT document consists of:

   o  a mechanism for clients to determine a server's available
      extensions

   o  a registry of NNTP service extensions

   The overview.fmt file LIST EXTENSIONS command is maintained by some news transport
     systems to contain the order described in which header information this document (see
   Section 6.1) and is
     stored in the overview databases mechanism for each newsgroup.  When
     executed, news article header fields clients to use to determine
   what extensions are displayed one line
     at available.

   The IANA shall maintain a time in the order in registry of NNTP service extensions.

   An extension is identified by a unique extension-label, which they are stored in is a
   string of 1 to 12 uppercase letters.  The extension-label will often
   be the
     overview database[9] following name of a new command that the 215 response.  When
     display extension adds.  However this
   is completed, the server will send not a period on requirement: an extension might not add any new commands or
   keywords.

   An extension is either a line
     by itself. If private extension or else it is included in
   the information IANA registry and is not available, defined in an RFC.  Such RFCs either must be
   on the server
     will return standards-track or must define an IESG-approved experimental
   protocol.

   The definition of an extension must include:

   o  a descriptive name for the 503 response.

     If extension
   o  the header has extension-label (which is returned by LIST EXTENSIONS to
      indicate to the word "full" (without quotes) after client that the
     colon, server supports this particular
      extension)

   o  the header's name is prepended to its field syntax, values, and meanings of any parameters following the
      extension-label in the output returned by the server.

     This is command is part of LIST EXTENSIONS

   o  any new NNTP commands associated with the optional OVER extension which
     includes

   o  the OVER command defined in section . If syntax and possible values of parameters associated with the
      new NNTP commands

   o  any new parameters the OVER

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     implemented. If that case, associates with any other
      pre-existing NNTP commands

   o  how support for the server MUST return a 501 error
     response when this command is presented by extension affects the client.

  9.5.2.1.1  Responses

            215 Information follows (multi-line response)
            501 Syntax Error
            503 Program error, function not performed

  9.5.2.1.2  Examples

     Example behavior of LIST OVERVIEW.FMT returning a list of newsgroups
          [S] 200 server and
      NNTP Service Ready
          [C] LIST OVERVIEW.FMT
          [S] 215 Order of fields client

   o  any increase in overview database.
          [S] Subject:
          [S] From:
          [S] Date:
          [S] Message-ID:
          [S] .
     Example the maximum length of LIST OVERVIEW.FMT returning an error
          [S] 200 NNTP Service Ready
          [C] LIST OVERVIEW.FMT
          [S] 503 program error, function not performed
  9.5.2.2  OVER

  OVER [range]
     The OVER command returns specific header information for commands over the
     article(s) value
      specified from the current selected group. The
     information returned in this document

   o  a specific statement about the response to effect on pipelining this command can be
     used by clients to follow discussion threads.
     The optional range argument extension
      may be any have (if any)

   The extension-label of the following:
     *  an article number
     *  an article number followed by a dash to indicate all
        following
     *  an article number followed by a dash followed by another
        article number

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     If no argument is specified, then information from the
     current article is displayed. Successful responses start private extensions MUST begin with
     a 224 response followed by the overview information for all
     matched messages. Once "X".  The
   extension-label of registered extensions MUST NOT begin with "X".

   A server MUST NOT provide any extension, whether or not listed in the
   output from LIST EXTENSIONS, unless it is complete, either a period is
     sent on registered
   extension or a line private extension.

   Except where stated otherwise, the commands in this document are
   understood (even if not supported) by itself. A newsgroup must have been selected
     earlier, else a 412 error response is returned. If no
     articles all servers and are not
   described in the range specified, list of features returned by the LIST EXTENSIONS
   command.

   A server returns MAY provide additional keywords - either for new commands or
   new variants of existing commands - as part of a 420
     error response. private extension.
   These new keywords MUST begin with "X".

   A 502 server MUST NOT send different response will be returned if the client
     only has permission codes to transfer articles. A 500 basic NNTP
   commands documented here or commands documented in registered
   extensions in response
     SHOULD be returned by servers that do not implement this
     command.

     The output consists to the availability or use of one line per article, sorted in
     numerical order a private
   extension.

10.1 Initial IANA registry

    The IANA's initial registry of article number. Each line NNTP service extensions consists of a
     number of fields separated by an US-ASCII TAB character. The
     first 8 fields MUST be the following, in order: article
     number, subject, author, date, message-ID, references, byte
     count, line count.

     The article number field should contain the
   these entries:

     Extension                   Label        Added behavior
     Specific article number
     (within the group). The line count and byte count are
     calculated by the server based on the actual size and number
     of lines numbers    LISTGROUP    Defined in this document
     Overview support            OVER         Defined in this document
     Header pattern matching     HDR          Defined in the article. The content of the rest this document

10.2 Standard extensions

   Each of the
     fields is formed by taking following sections describes an extension that a server
   MAY provide.  If the original header content (such
     as server provides the raw subject line from extension, it MUST include
   the article), removing all US-
     ASCII CRLF pairs, and then replacing each remaining US-ASCII
     NUL, TAB, CR, or LF character with a single US-ASCII space.
     The content of any subsequent field is given by appropriate extension label in the response to the LIST OVERVIEW.FMT command.  A field may be empty (in
     which case there will be two adjacent US-ASCII tabs, and a
     sequence of trailing US-ASCII tabs may be omitted).
     The server SHOULD not produce output for articles that no
     longer exist.
  9.5.2.2.1  Responses

            224 Overview information follows (multi-line
                response)
            412 No newsgroup currently selected
            420 No article(s) selected
            500 Command EXTENSIONS.
   If it does not recognized
            502 Program error, functions no performed

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  9.5.2.2.2  Examples

     Example of a successful retrieval provide it, it MUST NOT include the appropriate
   extension label.  The descriptions of overview information for
     an article (using no article number)
          [S] 200 NNTP Service Ready
          [C] GROUP misc.test
          [S] 211 1234 3000234 3002322 misc.test
          [C] OVER
          [S] 224 Overview information follows
              300234|I am just a test article|÷Demo User÷
               <nobody@example.com>|6 Oct 1998 04:38:40 -0500|
               <45223423@example.com>|<45454@example.net>|1234|
               17|Xref: news.example.com misc.test:3000363
          [S] .
     [Please note that facilities in each section are
   written as if the line that begins with 300234 extension is all one
     line that has been wrapped for readability. A vertical bar
     has been inserted to show where provided.  If it is not provided, the US-ASCII TAB
   entire section should
     actually be.]
     Example of be ignored.

   If the server provides an unsuccessful retrieval extension, it MUST implement all of overview information
     on an article by number
          [S] 200 NNTP Service Ready
          [C] GROUP misc.test
          [S] 211 1234 3000234 3002322 misc.test
          [C] OVER 300256
          [S] 420 No such article the
   commands in this group
     Example the specification of the extension except for those
   marked as optional.  If it does not provide an unsuccessful retrieval of overview information
     by number because no newsgroup was selected first
          [S] 200 NNTP Service Ready
          [C] OVER
          [S] 412 No newsgroup selected
     Example extension, it MUST NOT
   implement any of an attempt to retrieve an article when the current
     group selected is empty
          [S] 200 NNTP Service Ready
          [C] GROUP example.empty.newsgroup
          [S] 211 0 0 0 example.empty.newsgroup
          [C] OVER
          [S] 420 No current article selected

  9.5.3 commands in the specification of that extension.

10.3 The HDR Extension

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   This extension provides one new command, HDR. The label for
     this extension is HDR
  9.5.3.1  HDR

     HDR header range|<message-id>
     The HDR command is used to retrieve specific headers from
     specific articles in and has the currently extension label
   LISTGROUP.

10.3.1 LISTGROUP

10.3.1.1 Usage

   Syntax
      LISTGROUP [ggg]

   Responses
      211   Article numbers follow (multiline)
      411   No such newsgroup
      412   No newsgroup selected group.

     The required header parameter is the [1]

   Parameters
      ggg = name of a header line
     (e.g.  "subject") in a newsgroup article. See RFC-1036 for a
     list of valid header lines.
   [1] The required range argument may
     be any of the following:
     *  an article number
     *  an article number followed by a dash 412 response can only occur if no group has been specified.

10.3.1.2 Description

   The LISTGROUP command is used to indicate all
        following
     *  an article number followed by get a dash followed by another listing of all the article number.

     The required message-id argument indicates
   numbers in a specific
     article. particular newsgroup.

   The range and message-id arguments are mutually
     exclusive.

     A successful response consists optional parameter ggg is the name of a 221 code followed by the
     output newsgroup to be
   selected (e.g.  "news.software.misc").  A list of valid newsgroups
   may be obtained from the LIST ACTIVE command. The output consists of one line for
     each article where  If no group is
   specified, the relevant header current selected newsgroup is used.

   OUTSTANDING ISSUE

      On at least some servers the 211 response line exists. is the same as with
      GROUP.  Should this be a requirement?

   The line
     consists list of the article number, numbers is returned as a US-ASCII space, multi-line response
   following the 211 response code.  It contains one number per line, is
   in numerical order, and then lists precisely those articles that exist in
   the contents group.

   When a valid group is selected by means of this command, the header (without current
   selected newsgroup MUST be set to that group and the header name). A valid
     response includes current article
   number MUST be set to the first article in the group.  If an empty list (indicating that there were
     no matches). Once
   newsgroup is selected, the output current article pointer is complete, a period made invalid.
   If an invalid group is sent on
     a line specified, the current selected newsgroup and
   current article number MUST NOT be changed.

   The LISTGROUP command MAY be used by itself. If a client as a replacement for
   the optional argument is GROUP command in establishing a message-id valid current selected newsgroup
   and no such current article exists, number.

   If the group specified is not available on the server, a 430 error 411 response shall
   MUST be returned. A 502 response shall be returned if  If no group is specified and the client only
     has permission to transfer articles. A 500 current selected
   newsgroup is invalid, a 412 response SHOULD MUST be
     issued by all servers that do not recognize this command.
  9.5.3.1.1  Responses

            221  Header follows (multi-line response)
            412  No newsgroup selected
            430  No such article
            500  Command not recognized

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            502  Program error, function not performed

  9.5.3.1.2 returned.

10.3.1.3 Examples

   Example of a successful retrieval of subject lines from a
     range of articles
          [S] 200 NNTP Service Ready LISTGROUP on an empty group:

      [C] GROUP misc.test LISTGROUP example.empty.newsgroup
      [S] 211 1234 3000234 3002322 misc.test
          [C] HDR Subject 3000234-300238
          [S] 221 Header Follows
          [S] 3000234 I am just a test article
          [S] 3000237 Re: I am just a test list of article
          [S] 3000238 Ditto numbers follows
      [S] .

   Example of LISTGROUP on a successful retrieval of header from an article
     by message-id
          [S] 200 NNTP Service Ready valid current selected newsgroup:

      [C] GROUP misc.test
      [S] 211 1234 2000 3000234 3002322 misc.test selected
      [C] HDR subject <i.am.a.test.article@example.com> LISTGROUP
      [S] 221 Header information 211 list follows
      [S] 3000345 I am just a test article
          [S] .
     Example of an unsuccessful retrieval of a header from an
     article by message-id
          [S] 200 NNTP Service Ready
          [C] HDR subject <i.am.not.there@example.com> 3000234
      [S] 430 No Such Article Found
     Example of an unsuccessful retrieval of headers from articles
     by number because no newsgroup was selected first 3000237
      [S] 200 NNTP Service Ready
          [C] HDR subject 300256- 3000238
      [S] 412 No newsgroup selected
     Example of an unsuccessful retrieval of headers from articles
     by message-id because no newsgroup was selected first 3000239
      [S] 200 NNTP Service Ready
          [C] HDR subject <i.am.a.test.article@example.com> 3002322
      [S] 412 No newsgroup selected .

   Example of retrieving header information when the current LISTGROUP failing because no group has been selected:

      [Assumes current selected newsgroup is empty

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      [C] LISTGROUP
      [S] 200 NNTP Service Ready 412 no current group
      [C] GROUP example.empty.newsgroup example.is.sob.bradner.or.barber
      [S] 211 0 0 0 example.empty.newsgroup 411 no such group
      [C] HDR subject 0- LISTGROUP
      [S] 221 Headers follow
              .
     Example 412 no current group

10.4 Article metadata

   The OVER and HDR extensions refer to the concept of "article
   metadata".  This is data about articles that does not occur within
   the article itself.  Each metadata item has a failure due to restrictions configured into name which MUST begin
   with a colon.  Note that a historical feature of the LIST
   OVERVIEW.FMT command means that metadata names SHOULD NOT end with
   ":full".

   When generating a metadata item, the server
          [S] 200 NNTP Service Ready
          [C] GROUP news.group
          [S] 211 1234 3000234 3002322 misc.test
          [C] HDR Subject 3000234-300238
          [S] 502 Service Unavailable

  10 MUST compute it for
   itself and MUST NOT trust any related value provided in the article.
   (In particular, a Lines: or Bytes: header in the article MUST NOT be
   assumed to specify the correct number of lines or bytes in the
   article.)

   This specification defines two metadata items: ":bytes" and ":lines".
   Implementations and other extensions may define other metadata items.

10.4.1 The CONCLUSION Step

  10.1  QUIT

     QUIT :bytes metadata item

   The server process :bytes metadata item for an article is a decimal integer.  It
   MUST equal the number of octets in the entire article - headers,
   body, and separating blank line - except that the US-ASCII CRLF at
   the end of each line MAY (but SHOULD NOT) be counted as a single
   octet.

   OUTSTANDING ISSUE

      Should this be called ":octets" instead? Or should it be a count
      of UTF characters rather than octets?

10.4.2 The :lines metadata item

   The :lines metadata item for an article is a decimal integer.  It
   MUST acknowledge equal the QUIT command and then
     close number of lines in the connection to article body (excluding the client.  This
   blank line separating headers and body); equivalently, it is two less
   than the preferred
     method for a client to indicate number of US-ASCII CRLF pairs that it has finished all its
     transactions with the NNTP server.

     If a client simply disconnects (or the connection times out
     or some other fault occurs), the server MUST gracefully cease
     its attempts to service the client, disconnecting from its
     end if necessary.

  10.1.1  Responses

            250 Connection closing

  10.1.2  Example

          [S] 200 NNTP Service Ready
          [C] QUIT
          [S] 205 closing connection
             [Server closes connection.]

  11  Other Keywords

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     There are other keywords BODY command would
   return for that may be used at any time between
     the beginning of a session and its termination.  Using these
     keywords does not alter any state information, but article (the extra two are those following the
   response generated from code and the use of these keywords may provide
     useful information to clients that use them.

  11.1  DATE

     DATE termination octet).

10.5 The OVER extension

   This command exists extension provides two commands, OVER and LIST OVERVIEW.FMT.
   The label for this extension is OVER.

   The OVER extension provides access to help clients find out the current
     Coordinated Universal Time[10] overview database [8],
   which is a database of header lines extracted from incoming articles.
   Only certain headers are included in the server's perspective.
     This database.  The database also
   includes some article metadata.

   The information stored in the database may change over time.  The
   LIST OVERVIEW.FMT command MUST NOT be used as a substitute for NTP[11],
     but to provide describes the information that might would be useful when using
     the NEWNEWS command (see section 11.4). A system providing
     NNTP service SHOULD implement NTP
   stored for an article arriving at the purposes of keeping
     the system clock as accurate same time as possible.

     This the command was
   executed.

10.5.1 OVER

10.5.1.1 Usage

   Syntax
      OVER [range]

   Responses
      224   Overview information follows (multiline)
      412   No newsgroup selected
      420   Current article number is invalid
      423   No articles in that range

   Parameters
      range = Article(s) to return information for

10.5.1.2 Description

   The OVER command returns a one-line response code the contents of 111 followed
     by the date headers and time on the server metadata in
   the form
     YYYYMMDDhhmmss. This date and time is presented in
     Coordinated Universal Time.

  11.1.1  Response

            111 YYYYMMDDhhmmss Current date and time on server
                               presented in Coordinated
                               Universal Time

  11.1.2  Example

          [S] 200 NNTP Service Ready
          [C] DATE
          [S] 111 19990623135624

  11.2  The HELP Command

     HELP
     This command provides a short summary of commands that are
     understood by this implementation of database for the server. article(s) specified from the current selected
   newsgroup.

   The help
     text will optional range argument may be presented as a textual response terminated any of the following:

   o  an article number

   o  an article number followed by a
     single period on dash to indicate all following

   o  an article number followed by a line dash followed by itself.

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     This text another article
      number

   If no argument is not guaranteed to specified, then the current article number is used.

   If the information is available, it is returned as a multi-line
   response following the 224 response code.  If the current selected
   newsgroup is invalid, a 412 response MUST be returned.  If there are
   no articles in the range specified, a 423 response MUST be in returned.
   If OVER is sent without any particular format arguments and SHALL NOT be used by clients as a replacement for the
     LIST EXTENSIONS command described in section 8.1.

  11.2.1  Responses

            100 Help text follows (multi-line response)

  11.2.2  Example

          [S] 200 NNTP Service Ready
          [C] HELP
          [S] 100 Help text follows
          [S] This is some help text. There current article number
   is no specific
          [S] formatting requirement for invalid, a 420 response MUST be returned.  If the client does not
   have permission to access the overview database, a 502 response MUST
   be returned.

   OUTSTANDING ISSUE

      Should this test, though
          [S] it be 502 ("not permitted") or 503 ("there is customary for it to list no overview
      database")? In which case, why provide the valid commands
          [S] and give command?

   For a brief definition successful response, the output consists of what they do
          [S] .

  11.3  NEWGROUPS

     NEWGROUPS date time [GMT]
     A list one line per
   article, sorted in numerical order of newsgroups created since <date article number.  Each line
   consists of a number of fields separated by an US-ASCII TAB
   character.  A field may be empty (in which case there will be two
   adjacent US-ASCII TABs), and time> a sequence of trailing US-ASCII TABs may
   be omitted.

   The first 8 fields MUST be
     listed the following, in order:

      article number
      "Subject" header
      "From" header
      "Date" header
      "Message-ID" header
      "References" header
      :bytes metadata item
      :lines metadata item
   Any subsequent fields are the same format as contents of the LIST command.

     The date is sent as 6 or 8 digits other headers and
   metadata held in the format [XX]YYMMDD,
     where XX database.

   For the five mandatory headers, the content of each field MUST be
   based on the original header with the header name and following colon
   and space removed.  If the article does not contain that header, or
   if there is nothing following the first two digits of colon and space, the year, YY is field MUST be
   empty.  For the last two digits mandatory metadata items, the content of the year, MM is
   field MUST be just the two digits of value, with no other text.

   For all subsequent fields that contain headers, the month
     (with leading zero, if appropriate), and DD is content MUST be
   based on the day of entire header including the
     month (with leading zero, if appropriate). If name.  For all subsequent
   fields that contain metadata, the first two
     digits field consists of the year are not specified, metadata
   name, a single US-ASCII space, and then the year is to be taken
     from value.

   For all fields, the current century if YY value is smaller than processed by first removing all US-ASCII
   CRLF pairs and then replacing each remaining US-ASCII NUL, TAB, CR,
   or equal to LF character with a single US-ASCII space (for example, CR LF LF
   TAB will become two spaces).  If there is no such header in the current year, otherwise
   article, or no such metadata item, or no header or item stored in the year is from
   database for that article, the previous
     century.

     Time must also be specified.  It must corresponding field MUST be as 6 digits HHMMSS
     with HH being hours in empty.

   The server SHOULD NOT produce output for articles that no longer
   exist.

10.5.1.3 Examples

   In the 24-hour clock 00-23, MM minutes
     00-59, first two examples, US-ASCII tab has been replaced by vertical
   bar and SS seconds 00-60, which allows some lines have been folded for readability.

   Example of a successful retrieval of overview information for an
   article (using no article number):

      [C] GROUP misc.test
      [S] 211 1234 3000234 3002322 misc.test
      [C] OVER
      [S] 224 Overview information follows
      [S] 300234|I am just a test article|"Demo User"
      <nobody@example.com>|6 Oct 1998 04:38:40 -0500|
      <45223423@example.com>|<45454@example.net>|1234|
      17|Xref: news.example.com misc.test:3000363
      [S] .

   Example of a successful retrieval of overview information for leap seconds.
     The token "GMT" specifies that a range
   of articles:

      [C] GROUP misc.test
      [S] 211 1234 3000234 3002322 misc.test
      [C] OVER 3000234-3000240
      [S] 224 Overview information follows
      [S] 300234|I am just a test article|"Demo User"
      <nobody@example.com>|6 Oct 1998 04:38:40 -0500|
      <45223423@example.com>|<45454@example.net>|1234|
      17|Xref: news.example.com misc.test:3000363
      [S] 3000235|Another test article|nobody@nowhere.to
      (Demo User)|6 Oct 1998 04:38:45 -0500|<45223425@to.to>||
      4818|37||Distribution: fi
      [S] 3000238|Re: I am just a test article|somebody@elsewhere.to|
      7 Oct 1998 11:38:40 +1200|<kfwer3v@elsewhere.to>|
      <45223423@to.to>|9234|51
      [S] .

   Note the date missing "References" and time are given Xref headers in
     Coordinated Universal Time. If the token "GMT" is omitted
     then second line,
   the date and time are specified missing trailing field(s) in the server's local
     timezone. Note first and last lines, and that
   there is no way using the protocol

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     specified in this memo to establish the server's local
     timezone.

     Note are only results for those articles that still exist.

   Example of an empty list (i.e., the text body returned by this
     command consists only unsuccessful retrieval of the terminating period) is a
     possible valid response, and indicates that there are
     currently no new newsgroups.

     Clients SHOULD make all queries using Coordinated Universal
     Time (i.e. overview information on an
   article by including the ˘GMT÷ parameter) when possible.

  11.3.1  Responses

            231 List of new newsgroups follows (multi-line
                response)

  11.3.2  Examples

     Example where there are new groups number:

      [C] GROUP misc.test
      [S] 200 NNTP Service Ready 211 1234 3000234 3002322 misc.test
      [C] NEWGROUPS 19990624 000000 GMT OVER 300256
      [S] 231 list 420 No such article in this group

   Example of new newsgroups follows
          [S] alt.rfc-writers.recovery
          [S] tx.natives.recovery an unsuccessful retrieval of overview information by
   number because no newsgroup was selected first:

      [Assumes current selected newsgroup is invalid.]
      [C] OVER
      [S] . 412 No newsgroup selected

   Example where there are no new groups of an attempt to retrieve information when the current
   selected newsgroup is empty:

      [C] GROUP example.empty.newsgroup
      [S] 200 NNTP Service Ready 211 0 0 0 example.empty.newsgroup
      [C] NEWGROUPS 19990624 000000 GMT OVER
      [S] 231 list of new newsgroups 420 No current article selected

10.5.2 LIST OVERVIEW.FMT

10.5.2.1 Usage
   Syntax
      LIST OVERVIEW.FMT

   Responses
      215   Information follows
          [S] .

  11.4  NEWNEWS

     NEWNEWS wildmat date time [GMT]
     A list of message-ids of articles posted or received on (multiline)
      503   Facility not available

10.5.2.2 Description

   OUTSTANDING ISSUE

      Should this be optional even when the
     server to OVER extension is provided?
      If so, is there a point in the list 503 response?

   The LIST OVERVIEW.FMT command returns a description of newsgroups that match the wildmat since
     "date" will be listed. fields in
   the database.  The format of fields MUST be listed in the listing order that they will
   be one
     message-id per line, as though text were being sent. The
     order of returned by the response has no specific significance and OVER command for a newly-received article (the
   information stored for articles may
     vary from response to change over time).

   If the information is available, it is returned as a multi-line
   response in following the same session. 215 response code.  If a
     message-id appears more than once it has the same meaning as

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     if it appears only once. A single information is not
   available, a 503 response MUST be returned.  The information contains
   one line consisting solely per field in the order they are returned by the OVER
   command; he first 7 lines MUST be exactly:

       Subject:
       From:
       Date:
       Message-ID:
       References:
       :bytes
       :lines

    except that, for compatibility with existing implementations, the
   last two lines MAY instead be:

       Bytes:
       Lines:

    even though they refer to metadata, not headers.

   All subsequent lines MUST consist of
     one period either a header name followed by CR-LF will terminate
   ":full", or the list.

     Date and time name of a piece of metadata.

   There are no leading or trailing spaces in the same format as the NEWGROUPS
     command. output.

   Note that an empty list (i.e., the text body returned by this
     command consists only 7 fixed lines describe the 2nd to 8th fields of the terminating period)
   OVER output.  The "full" suffix is a
     possible valid response, and indicates reminder that there is
     currently no new news.

     Clients SHOULD make all queries the corresponding
   fields include the header name.

   This command MAY generate different results if used more than once in Coordinated Universal Time
     (i.e. by
   a session.

10.5.2.3 Examples

   Example of LIST OVERVIEW.FMT output corresponding to the example OVER
   output above, using the preferred format:

      [C] LIST OVERVIEW.FMT
      [S] 215 Order of fields in overview database.
      [S] Subject:
      [S] From:
      [S] Date:
      [S] Message-ID:
      [S] References:
      [S] :bytes
      [S] :lines
      [S] Xref:full
      [S] Distribution:full
      [S] .

   Example of LIST OVERVIEW.FMT output corresponding to the example OVER
   output above, using the ˘GMT÷ parameter) when possible.

  11.4.1  Responses

       230 List alternative format:

      [C] LIST OVERVIEW.FMT
      [S] 215 Order of fields in overview database.
      [S] Subject:
      [S] From:
      [S] Date:
      [S] Message-ID:
      [S] References:
      [S] Bytes:
      [S] Lines:
      [S] Xref:full
      [S] Distribution:full
      [S] .

   Example of LIST OVERVIEW.FMT returning an error:

      [C] LIST OVERVIEW.FMT
      [S] 503 overview.fmt not available

10.6 The HDR extension

   This extension provides one new command: HDR.  The label for this
   extension is HDR.

10.6.1 HDR

10.6.1.1 Usage

   Syntax
      HDR header range
      HDR header message-id
      HDR header

   Responses

      First form (range specified)
         225   Headers follow (multiline)
         412   No newsgroup selected
         423   No articles in that range

      Second form (message-id specified)
         225   Headers follow (multiline)
         430   No article with that message-id

      Third form (current article number used)
         225   Headers follow (multiline)
         412   No newsgroup selected
         420   Current article number is invalid

   Parameters
      header     = name of header, without the colon
      range      = number(s) of new articles by
      message-id follows (may be a
            multi-line response)

  11.4.2  Examples

     Example where there are new articles
          [S] 200 NNTP Service Ready
          [C] NEWNEWS news.*,sci.* 19990624 000000 GMT
          [S] 230 list of new articles by = message-id follows
          [S] <i.am.a.new.article@example.com>
          [S] <i.am.another.new.article@example.com>

     Example where there are no new articles
          [S] 200 NNTP Service Ready
          [C] NEWNEWS alt.* 19990624 000000 GMT
          [S] 230 list of new article

10.6.1.2 Description

   The HDR command retrieves specific headers from an article or
   specified range of articles in the current selected newsgroup, or
   from an article specified by message-id follows
          [S] .

  12  Framework for NNTP Extensions

     Although NNTP is widely and robustly deployed, some parts of message-id.  It can also return certain
   metadata about the Internet community might wish to extend article or articles.

   The required header parameter is the NNTP service.
     This memo defines name of a means whereby header (e.g.
   "subject") in an extended NNTP client may
     query the server to determine the service extensions that it
     supports.

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     It must be emphasized that any extension to article, or the NNTP service
     should not be considered lightly. NNTP's strength comes
     primarily from its simplicity.  Experience with many
     protocols has shown that:

     Protocols with few options tend towards ubiquity, whilst
     protocols with many options tend towards obscurity.

     This means that each name of a metadata item, and is
   case-insensitive.  See RFC 1036 [6] for a list of valid header lines.
   Names of metadata items always include a colon.  Except where stated
   otherwise, metadata items are treated as if they were header values,
   and every extension, regardless of its
     benefits, must references to headers in this description apply equally to
   metadata items.

   OUTSTANDING ISSUE

      Should this be carefully scrutinized with respect changed to its
     implementation, deployment, and interoperability costs. In
     many cases, require the cost name to *begin* with a
      colon?

   The range parameter may be any of extending the NNTP service will
     likely outweigh following:

   o  an article number

   o  an article number followed by a dash to indicate all following

   o  an article number followed by a dash followed by another article
      number

   The message-id argument indicates a specific article.  As shown by
   the benefit.

     Given this environment, syntax, the framework for range and message-id arguments are mutually
   exclusive; if neither are specified, the extensions
     described in this memo consists of:
     * current article number is
   used.

   If the information is available, it is returned as a mechanism multi-line
   response following the 225 response code and contains one line for clients to determine a server's available
        extensions
     *  a registry of NNTP service extensions
   each article where the relevant header line exists.  The LIST EXTENSIONS command is described in section 8.1 line
   consists of
     this memo the article number, a US-ASCII space, and then the
   contents of the header (without the header name or the colon and
   space that follow it) or metadata item.  If the article is specified
   by message-id rather than by article range, the mechanism for clients to use to
     determine what extensions article number is
   given as "0".

   Header contents are available for client use.

     The IANA shall maintain modified as follows: all US-ASCII CRLF pairs are
   removed, and then each remaining US-ASCII NUL, TAB, CR, or LF
   character is replaced with a registry of NNTP service
     extensions.

     An extension single US-ASCII space.  (Note that this
   is identified the same transformation as is performed by a unique extension-label, which the OVER extension.)

   The header content is in all cases taken from the article.  This
   means that, for example, a string request for the header "Lines" returns the
   contents of 1 to 12 uppercase letters. The extension-label
     will often be the name "Lines" header of a new command that the extension
     adds. However this is not a requirement: an extension might specified articles, if any, not add any new commands or keywords.

     An extension is either a private extension
   the line count metadata or else it is
     included in any other server-generated value.  If the IANA registry and is defined
   header occurs in an RFC. Such
     RFCs either must be on the standards-track or must define an
     IESG-approved experimental protocol.

     The definition of an extension must include:
     * a descriptive name for given article multiple times, only the extension

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     * value of
   the extension-label (which first occurrence is returned by LIST EXTENSIONS
        to indicate to HDR.

   If the client requested header is not present in the article or if it is
   present but empty, a line for that article is included in the server supports this
        particular extension)
     * output
   but the syntax, values, and meanings header content portion of the line is empty (the space after
   the article number MAY be retained or omitted).  If any parameters
        following article
   number in the extension-label provided range does not exist in the output of LIST
        EXTENSIONS
     *  any new NNTP keywords associated with group, no line for
   that article number is included in the extension
     * output.

   If the optional argument is a message-id and no such article exists,
   a 430 response MUST be returned.  If the syntax optional argument is not a
   message-id and possible values of parameters associated
        with the new NNTP keywords
     *  any new parameters current selected newsgroup is invalid, a 412
   response MUST be returned.  If the extension associates optional argument is an article
   number or number range and no article with any other
        pre-existing NNTP keywords
     *  how support for that number or in that
   number range exists in the extension affects current selected newsgroup, a 423 response
   MUST be returned.  If HDR is sent without any arguments and the behavior of
   current article number is invalid, a 420 response MUST be returned.
   A server MAY only allow HDR commands for a limited set of headers and NNTP client
     *  any increase
   metadata items (such as those present in the maximum length overview database).  If
   so, it MUST respond with a 503 response to attempts to request other
   headers, rather than returning erroneous results such as a successful
   empty response.

10.6.1.3 Examples

   Example of commands over the
        value specified in this memo
     * a specific statement about the effect on streaming this
        extension may have (if any)

     The extension-label successful retrieval of subject lines from a range of
   articles (3000235 has no Subject header, and 3000236 is missing):

      [C] GROUP misc.test
      [S] 211 1234 3000234 3002322 misc.test
      [C] HDR Subject 3000234-300238
      [S] 225 Headers follow
      [S] 3000234 I am just a test article
      [S] 3000235
      [S] 3000237 Re: I am just a test article
      [S] 3000238 Ditto
      [S] .

   Example of a successful retrieval of line counts from a range of
   articles:

      [C] GROUP misc.test
      [S] 211 1234 3000234 3002322 misc.test
      [C] HDR :lines 3000234-300238
      [S] 225 Headers follow
      [S] 3000234 42
      [S] 3000235 5
      [S] 3000237 11
      [S] 3000238 2378
      [S] .

   Example of private extensions MUST begin with
     "X". The extension-label a successful retrieval of registered extensions MUST NOT
     begin with "X".

     Any keyword values presented in the NNTP response that do not
     begin with "X" MUST correspond to subject line from an article
   by message-id:

      [C] GROUP misc.test
      [S] 211 1234 3000234 3002322 misc.test
      [C] HDR subject <i.am.a.test.article@example.com>
      [S] 225 Header information follows
      [S] 0 I am just a standard, standards-
     track, or IESG-approved experimental NNTP service extension
     registered with IANA.  A conforming server MUST NOT offer non
     "X" prefixed keyword values that are not described in test article
      [S] .

   Example of a
     registered extension.

     Except where stated otherwise, successful retrieval of the commands in this memo are
     understood (even if not supported) by all servers and are not
     described in subject line from the list
   current article:

      [C] GROUP misc.test
      [S] 211 1234 3000234 3002322 misc.test
      [C] HDR subject
      [S] 225 Header information follows
      [S] 3000234 I am just a test article
      [S] .

   Example of features returned by the LIST
     EXTENSIONS command.

     A server MAY provide additional keywords - either new
     commands or new parameters to existing commands - as part an unsuccessful retrieval of a private extension. These new keywords MUST begin with "X".

     A server MUST NOT send different response codes to basic NNTP
     commands documented here or commands documented in registered
     extensions in response to the availability or use header from an article by
   message-id:

      [C] HDR subject <i.am.not.there@example.com>
      [S] 430 No Such Article Found

   Example of a
     private extension.

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  12.1  Initial IANA Registry

     The IANA's initial registry an unsuccessful retrieval of headers from articles by
   number because no newsgroup was selected first:

      [Assumes current selected newsgroup is invalid.]
      [C] HDR subject 300256-
      [S] 412 No newsgroup selected

   Example of NNTP service extensions
     consists an unsuccessful retrieval of these entries:
    Service Extension   NNTP Extension Label    Added Behavior
    Overview Support           OVER         Defined in this memo
    Specific Article
                              LISTGROUP       Defined in this memo
         Numbers
     Header Pattern headers because the current
   selected newsgroup is empty:

      [C] GROUP example.empty.newsgroup
      [S] 211 0 0 0 example.empty.newsgroup
      [C] HDR          Defined subject 1-
      [S] 423 No articles in this memo
        Matching

  13 that range

   Example of an unsuccessful retrieval of headers because the server
   does not allow HDR commands for that header:

      [C] GROUP misc.test
      [S] 211 1234 3000234 3002322 misc.test
      [C] HDR Content-Type 3000234-300238
      [S] 503 HDR not permitted on Content-Type

11. Augmented BNF Syntax for NNTP Commands

   This syntax defines the non-terminal "command". The non-
     terminal "parameter" is used for command parameters whose
     syntax is specified elsewhere. The syntax is in alphabetical
     order. "command-line".  Note that ABNF
   strings are case insensitive.

        article-command

     command-line = "ARTICLE" [1*WSP (msg-id / article-
              number)] *WSP CRLF
        article-number = 1*16DIGIT
        argument = parameter ; excluding sequence ".."
        body-command = "BODY" [1*WSP (msg-id / article-number)]
              *WSP CRLF command EOL
     command = article-command /
           body-command /
           date-command /
           group-command /
           hdr-command /
           head-command /
           help-command /
           ihave-command /
           last-command /
           list-active-command /
           list-active-times-command /
           list-distrib-pats-command /
           list-distributions-command /
           list-extensions-command /
           list-newsgroups-command /
           list-overview-fmt-command /
              list-command /
           listgroup-command /
           mode-reader-command /

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           newgroups-command /
           newnews-command /
           next-command /
           over-command /
              hdr-command /
           post-command /
           quit-command /
           stat-command
        CR /
           x-command
     article-command = %x0D
        CRLF "ARTICLE" [article-ref]
     body-command = CR LF "BODY" [article-ref]
     date-command = "DATE" *WSP CRLF
        date = 6*8DIGIT
        DIGIT = %x30-39
     group-command = "GROUP" 1*WSP wildmat *WSP CRLF WS newsgroup-name
     hdr-command = "HDR" 1*WSP header 1*WSP (range / msg-id)
              *WSP CRLF WS header-meta-name [range-ref]
     head-command = "HEAD" [1*WSP (msg-id / article-number)]
              *WSP CRLF
        header = parameter [article-ref]
     help-command = "HELP" *WSP CRLF
        HT = %x09
     ihave-command = "IHAVE" 1*WSP msg-id *WSP CRLF WS message-id
     last-command = "LAST" *WSP CRLF
        LF
     list-active-command = %x0A "LIST" [WS "ACTIVE" [WS wildmat]]
     list-active-times-command = "LIST" 1*WSP WS "ACTIVE.TIMES"
              [1*WSP [WS wildmat] *WSP CRLF
        list-command = "LIST" [1*WSP "ACTIVE" [1*WSP wildmat]]
              *WSP CRLF
     list-distrib-pats-command = "LIST" 1*WSP WS "DISTRIB.PATS"
              *WSP CRLF
     list-distributions-command = "LIST" 1*WSP WS "DISTRIBUTIONS"
              *WSP CRLF
     list-extensions-command = "LIST" 1*WSP WS "EXTENSIONS" *WSP
              CRLF
     list-newsgroups-command = "LIST" 1*WSP WS "NEWSGROUPS" [1*WSP [WS wildmat] *WSP CRLF
     list-overview-fmt-command = "LIST" 1*WSP WS "OVERVIEW.FMT"
              *WSP CRLF
     listgroup-command = "LISTGROUP" [1*WSP wildmat] *WSP CRLF [WS newsgroup-name]
     mode-reader-command = "MODE" 1*WSP WS "READER" *WSP CRLF
        msg-id = <defined in section 9.1 of this memo>

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     newgroups-command = "NEWGROUPS" 1*WSP date 1*WSP time
              1*WSP "GMT"] *WSP CRLF WS date-time
     newnews-command = "NEWNEWS" 1*WSP WS wildmat 1*WSP date
           1*WSP time [1*WSP "GMT÷]*WSP CRLF WS date-time
     next-command = "NEXT" *WSP CRLF
     over-command = "OVER" [1*WSP [WS range] *WSP CRLF
        parameter = 1*(%x21-FF) ; generic command parameter
     post-command = "POST" *WSP CRLF
        quit-command = "QUIT" *WSP CRLF
        range = article-number ["-" [article-number]]
        SP
     quit-command = %x20 "QUIT"
     stat-command = "STAT" [1*WSP (msg-id [article-ref]
     x-command = x-command-name *(WS x-argument)
         ; Each extension command is specified fully elsewhere
     article-ref = WS (article-number / article-number)]
              *WSP CRLF
        time message-id)
     article-number = 1*16DIGIT
     date = [2DIGIT] 6DIGIT
        UTF-8-non-ascii
     date-time = UTF8-2 date WS time [WS "GMT"]
     header-meta-name = header-name / UTF8-3 metadata-name
     header-name = 1*header-name-char
     header-name-char = %x21-39 / UTF8-4 %x3B-7E ; exclude SP and :
     message-id = "<" 1*248message-id-char ">"
       ; subject to requirements in
   Section 7
   >
     message-id-char = %x21-3B / UTF8-5 %x3C /
              UTF8-6
        UTF8-1 %x3E-7E ; exclude SP < >
     metadata-name = %x80-BF
        UTF8-2 ":" 1*header-name-char
     newsgroup-name = %xC0-DF UTF8-1
        UTF8-3 1*wildmat-exact
     range = %xE0-EF 2UTF8-1
        UTF8-4 article-number ["-" [article-number]]
     range-ref = %xF0-F7 3UTF8-1
        UTF8-5 WS (range / message-id)
     time = %xF8-FB 4UTF8-1
        UTF8-6 6DIGIT
     x-command-name = %xFC-FD 5UTF8-1 3*12%x21-7E
     x-argument = 1*(%x21-7E / UTF-8-non-ascii)
     wildmat = wildmat-pattern *("," ["!"] wildmat-pattern)
     wildmat-pattern = 1*wildmat-item
     wildmat-item = wildmat-exact / wildmat-wild
     wildmat-exact = %x21-29 / %x2B / %x2D-3E / %x40-5A / %x5E-
              7F /UTF-8-non-ascii %x5E-7E /
          UTF-8-non-ascii  ; exclude * , ? [ \ ]
     wildmat-wild = "*" / "?"
        WSP
     CR = SP %x0D
     CRLF = CR LF
     DIGIT = %x30-39
     EOL = *(SP / HT) CRLF
     HT

  14 = %x09
     LF = %x0A
     SP = %x20
     UTF-8-non-ascii = UTF8-2 / UTF8-3 / UTF8-4 / UTF8-5 / UTF8-6
     UTF8-1 = %x80-BF
     UTF8-2 = %xC2-DF UTF8-1
     UTF8-3 = %xE0 %A0-BF UTF8-1 / %xE1-EC 2UTF8-1 /
              %xED %80-9F UTF8-1 / %xEE-EF 2UTF8-1
     UTF8-4 = %xF0 %90-BF 2UTF8-1 / %xF1-F7 3UTF8-1
     UTF8-5 = %xF8 %88-BF 3UTF8-1 / %xF9-FB 4UTF8-1
     UTF8-6 = %xFC %84-BF 4UTF8-1 / %xFD    5UTF8-1
     WS = 1*(SP / HT)

12. Security Considerations

   This section is meant meant to inform application developers, information
   providers, and users of the security limitations in NNTP as described
   by this document.  The discussion does not include definitive
   solutions to the problems revealed, though it does make some
   suggestions for reducing security risks.

12.1 Personal and Proprietary Information

   NNTP, because it was created to distribute network news articles,
   will forward whatever information is stored in those articles.
   Specification of that information is outside this scope of this
   document, but it is likely that some personal and/or proprietary
   information is available in some of those articles.  It is very
   important that designers and implementers provide informative
   warnings to users so personal and/or proprietary information in
   material that is added automatically to articles (e.g.  in headers)
   is not disclosed inadvertently.  Additionally, effective and easily
   understood mechanisms to inform application developers, manage the distribution of news articles
   SHOULD be provided to NNTP Server administrators, so that they are
   able to report with confidence the likely spread of any particular
   set of news articles.

12.2 Abuse of Server Log Information

   A server is in the position to save session data about a user's
   requests that might identify their reading patterns or subjects of
   interest.  This information providers, is clearly confidential in nature and users its
   handling can be constrained by law in certain countries.  People
   using the NNTP protocol to provide data are responsible for ensuring
   that such material is not distributed without the permission of any
   individuals that are identifiable by the published results.

12.3 Weak Authentication and Access Control

   There is no user-based or token-based authentication in the basic
   NNTP specification.  Access is normally controlled by server
   configuration files.  Those files specify access by using domain
   names or IP addresses.  However, this specification does permit the
   creation of extensions to the NNTP protocol itself for such purposes.
   While including such mechanisms is optional, doing so is strongly
   encouraged.

   Other mechanisms are also available.  For example, a proxy server
   could be put in place that requires authentication before connecting
   via the proxy to the NNTP server.

12.4 DNS Spoofing

   Many existing NNTP implementations authorize incoming connections by
   checking the IP address of that connection against the IP addresses
   obtained via DNS lookups of lists of domain names given in local
   configuration files.  Servers that use this type of authentication,
   and clients that find a server by doing a DNS lookup of the server
   name, rely very heavily on the Domain Name Service, and are thus
   generally prone to security limitations
     in NNTP as described by this memo. The discussion does not
     include definitive solutions attacks based on the deliberate
   misassociation of IP addresses and DNS names.  Clients and servers
   need to be cautious in assuming the problems revealed, though
     it does make some suggestions continuing validity of an IP
   number/DNS name association.

   In particular, NNTP clients and servers SHOULD rely on their name
   resolver for reducing security risks.

  14.1  Personal confirmation of an IP number/DNS name association,
   rather than caching the result of previous host name lookups.  Many
   platforms already can cache host name lookups locally when
   appropriate, and Proprietary Information

     NNTP, because it was created they SHOULD be configured to distribute network news
     articles, will forward whatever information do so.  It is stored in

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     those articles. Specification of that proper
   for these lookups to be cached, however, only when the TTL (Time To
   Live) information is outside
     this scope of this memo, but reported by the name server makes it is likely that some personal
     and/or proprietary
   the cached information is available in some will remain useful.

   If NNTP clients or servers cache the results of those
     articles. It host name lookups in
   order to achieve a performance improvement, they MUST observe the TTL
   information reported by DNS.  If NNTP clients or servers do not
   observe this rule, they could be spoofed when a previously accessed
   server's IP address changes.  As network renumbering is very important that designers and
     implementers provide informative warnings expected to users so
     personal and/or proprietary information is not disclosed
     inadvertently. Additionally, effective
   become increasingly common, the possibility of this form of attack
   will grow.  Observing this requirement thus reduces this potential
   security vulnerability.

   This requirement also improves the load-balancing behavior of clients
   for replicated servers using the same DNS name and easily understood
     mechanisms to manage reduces the distribution
   likelihood of news articles must
     be provided to NNTP Server administrators, so a user's experiencing failure in accessing sites that they are
     able
   use that strategy.

12.5 UTF-8 issues

   The UTF-8 specification [2] permits only certain sequences of octets
   and designates others as either malformed or "illegal".  The Unicode
   standard identifies a number of security issues related to report with confidence what information is illegal
   sequences and is not
     being forwarded in news articles passing though forbids their
     servers.

  14.2  Abuse generation by conforming implementations.

   Implementations of this specification MUST NOT generate malformed or
   illegal sequences and SHOULD detect them and take some appropriate
   action.  This could include:

   o  replacing such sequences by a "guessed" valid sequence (based on
      properties of Server Log Information

     A server is in the position to save session data about UTF-8 encoding);

   o  replacing such sequences by the sequence %xEF.BF.BD, which encodes
      the "replacement character";

   o  closing the connection;

   o  generating a
     user's requests that might identify their reading patterns or
     subjects 501 response code.

13. Acknowledgments

   The author acknowledges the original authors of interest. This information is clearly
     confidential NNTP as documented in nature
   RFC 977: Brian Kantor and its handling can be constrained by
     law in certain countries. People using Phil Lapsey.

   The author gratefully acknowledges the work of the NNTP protocol committee
   chaired by Eliot Lear.  The organization of this document was
   influenced by the last available draft from this working group.  A
   special thanks to
     provide data are responsible Eliot for ensuring that such material
     is not distributed without generously providing the permission of any individuals original
   machine-readable sources for that are identifiable by document.

   The author gratefully acknowledges the published results.

  14.3  Weak Authentication and Access Control

     There is no user-based or token-based authentication work of Marshall Rose & John
   G.  Meyers in RFC 1939 and the
     basic NNTP specification. Access work of the DRUMS working group,
   specifically RFC 1869, which is normally controlled by
     server configuration files. Those files specify access by
     using domain names or IP addresses. However, this memo does
     permit the creation basis of extensions to the NNTP protocol itself
     for such purposes. While including such mechanisms is
     optional, doing so is strongly encouraged.

     Other mechanisms are also available. For example, a proxy
     server could be put extensions
   mechanism detailed in place this document.

   OUTSTANDING ISSUE

      Why RFC 1939?

   The author gratefully acknowledges the authors of RFC 2616 for
   providing specific and relevant examples of security issues that requires authentication
     before connecting via
   should be considered for HTTP.  Since many of the proxy to same considerations
   exist for NNTP, those examples that are relevant have been included
   here with some minor rewrites.

   The author gratefully acknowledges the NNTP server.

  14.4  DNS Spoofing

     Many existing NNTP implementations authorize incoming
     connections comments and additional
   information provided by checking the IP address following individuals in preparing one or
   more of that connection

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     against the IP addresses obtained via DNS lookups of lists progenitors of
     domain names given in local configuration files.  Servers
     that use this type document:

      Russ Allbery <rra@stanford.edu>
      Wayne Davison <davison@armory.com>
      Chris Lewis <clewis@bnr.ca>
      Tom Limoncelli <tal@mars.superlink.net>
      Eric Schnoebelen <eric@egsner.cirr.com>
      Rich Salz <rsalz@osf.org>

   This work was motivated by the work of authentication, various news reader authors
   and clients that find a news server by doing a DNS lookup authors, which includes those listed below:

   Rick Adams
      Original author of the server name, rely very
     heavily on the Domain Name Service, and are thus generally
     prone NNTP extensions to security attacks based on the deliberate
     misassociation of IP addresses and DNS names. Clients RN news reader and
     servers need to be cautious in assuming the continuing
     validity
      last maintainer of an IP number/DNS name association.

     In particular, NNTP clients and servers SHOULD rely on their
     name resolver for confirmation Bnews

   Stan Barber
      Original author of an IP number/DNS name
     association, rather than caching the result of previous host
     name lookups. Many platforms already can cache host name
     lookups locally when appropriate, and they SHOULD be
     configured to do so. It is proper for these lookups NNTP extensions to be
     cached, however, only when the TTL (Time To Live) information
     reported by the name server makes it likely news readers that
      are part of Bnews
   Geoff Collyer
      Original author of the cached
     information will remain useful.

     If NNTP clients or servers cache OVERVIEW database proposal and one of the results
      original authors of CNEWS

   Dan Curry
      Original author of host name
     lookups in order to achieve a performance improvement, they
     MUST observe the TTL information reported by DNS.
     If NNTP clients or servers do not observe this rule, they
     could be spoofed when a previously accessed server's IP
     address changes. As network renumbering is expected xvnews news reader

   Wayne Davison
      Author of the first threading extensions to become
     increasingly common, the possibility RN news reader
      (commonly called TRN)

   Geoff Huston
      Original author of this form ANU NEWS

   Phil Lapsey
      Original author of attack
     will grow. Observing this requirement thus reduces this
     potential security vulnerability.

     This requirement also improves the load-balancing behavior of
     clients UNIX reference implementation for replicated servers using NNTP

   Iain Lea
      Original maintainer of the same DNS name and
     reduces TIN news reader

   Chris Lewis
      First known implementer of the likelihood AUTHINFO GENERIC extension

   Rich Salz
      Original author of a user's experiencing failure in
     accessing sites that use that strategy.

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  15 INN

   Henry Spencer
      One of the original authors of CNEWS

   Kim Storm
      Original author of the NN news reader

   Finally, the present author gratefully acknowledges the vast amount
   of work put into previous drafts by the previous author:

      Stan Barber <sob@academ.com>

Normative References

     1

   [1]   Kantor, B B. and P. Lapsley, "Network News Transfer Protocol",
        RFC-977, U.C. San Diego and U.C. Berkeley, February,
         RFC 977, February 1986.
     2

   [2]   Yergeau, F., "UTF-8, a transformation format of ISO 10646", RFC
         2279, Alis Technologies, January, January 1998.
     3 Coded

   [3]   American National Standards Institute, "Coded Character Set-7-bit Set -
         7-bit American Standard Code for Information Interchange, Interchange", ANSI x3.4-1986.
     4
         X3.4, 1986.

   [4]   Bradner, Scott, "Keywords S., "Key words for use in RFCs to Indicate Requirement
         Levels", RFC-2119, Harvard University, March, BCP 14, RFC 2119, March 1997.
     5 Salz, Rich, Manual Page for wildmat(3) from the INN 1.4
        distribution, UUNET Technologies, Revision 1.10, April,
        1992.
     6

   [5]   Crocker, D. and P. Overell, P., "Augmented BNF for Syntax
         Specifications: ABNF", RFC-2234, Internet Mail Consortium
        and Demon Internet, Ltd., November, RFC 2234, November 1997.
     7

   [6]   Horton, M. and R. Adams, R., "Standard for the Interchange interchange of USENET
         messages", RFC 1036, AT&T Bell Laboratories and The
        Center for Seismic Studies, December, December 1987.
     8

   [7]   Resnick, P., Editor, "Internet Message Format", RFC 2822,
        QUALCOMM Incorporated, April 2001.
     9

   [8]   Robertson, Rob, R., "FAQ: Overview database / NOV General
         Information",
        ftp://ftp.uu.net/networking/news/nntp/inn/faq-nov.Z,
        January, January 1995.
     10

   [9]   International Telecommunications Union-Radio, "Glossary", Union - Radio, "Glossary,
         ITU-R Recommendation TF.686-1", ITU-R Recommendation TF.686-1, October,
         October 1997.
     11

   [10]  Mills, David L., D., "Network Time Protocol (Version 3), 3) Specification, Implementation and Analysis", RFC-1305,
        University of Delaware,
         Implementation", RFC 1305, March 1992.

  16  Notes

     UNIX is a registered trademark of the X/Open Company Ltd.

  17  Acknowledgments

     The author acknowledges

Informative References

   [11]  Salz, R., "Manual Page for wildmat(3) from the original authors of NNTP as
     documented in RFC 977: Brian Kantor INN 1.4
         distribution, Revision 1.10", April 1992.

   [12]  Rose, M., "Writing I-Ds and Phil Lapsey.

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         1999.

Author's Address

   Clive D.W. Feather
  Expires: July 31, 2003
   Thus plc
                                                       January 2003

     The author gratefully acknowledges the work of the NNTP
     committee chaired by Eliot Lear.
   322 Regents Park Road
   London  N3 2QQ
   GB

   Phone: +44 20 8371 1138
   Fax:   +44 870 051 9937
   URI:   http://www.davros.org/

Intellectual Property Statement

   The organization of this
     memo was influenced by the last available draft from this
     working group. A special thanks to Eliot for generously
     providing IETF takes no position regarding the original machine-readable sources for validity or scope of any
   intellectual property or other rights that
     document.

     The author gratefully acknowledges might be claimed to
   pertain to the work implementation or use of the Marshall
     Rose & John G. Meyers technology described in RFC 1939 and the work of
   this document or the DRUMS
     working group, specifically RFC 1869, extent to which is the basis of any license under such rights
   might or might not be available; neither does it represent that it
   has made any effort to identify any such rights.  Information on the NNTP extensions mechanism detailed
   IETF's procedures with respect to rights in this memo.

     The author gratefully acknowledges the authors standards-track and
   standards-related documentation can be found in BCP-11.  Copies of RFC 2616
   claims of rights made available for providing specific publication and relevant examples any assurances of security
     issues that should
   licenses to be considered for HTTP. Since many of made available, or the
     same considerations exist result of an attempt made to
   obtain a general license or permission for NNTP, those examples that are
     relevant have been included here with some minor rewrites.

     The author gratefully acknowledges the comments and
     additional information provided use of such
   proprietary rights by the following individuals
     in preparing one implementors or more of the progenitors users of this memo:
        Russ Allbery <rra@stanford.edu>
        Wayne Davison <davison@armory.com>
        Chris Lewis <clewis@bnr.ca>
        Tom Limoncelli <tal@mars.superlink.net>
        Eric Schnoebelen <eric@egsner.cirr.com>
        Rich Salz <rsalz@osf.org>

     This work was motivated by specification can
   be obtained from the work of various news reader
     authors and news server authors, IETF Secretariat.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights which includes those listed
     below:
        Rick Adams-Original author of may cover technology that may be required to practice
   this standard.  Please address the NNTP extensions information to the
              RN news reader IETF Executive
   Director.

Full Copyright Statement

   Copyright (C) The Internet Society (2003).  All Rights Reserved.

   This document and last maintainer of Bnews
        Stan Barber-Original author translations of the NNTP extensions it may be copied and furnished to the
              news readers
   others, and derivative works that are part of Bnews.
        Geoff Collyer-Original author of the OVERVIEW database
              proposal comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and one of the original authors of CNEWS
        Dan Curry-Original author distributed, in whole or in part, without restriction of any
   kind, provided that the xvnews news reader
        Wayne Davison-Author of above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the first threading extensions copyright notice or references to the RN news reader (commonly called TRN).
        Geoff Huston-Original author of ANU NEWS
        Phil Lapsey-Original author of the UNIX reference
              implementation Internet Society or other
   Internet organizations, except as needed for NNTP
        Iain Lea-Original maintainer of the TIN news reader
        Chris Lewis-First known implementer purpose of
   developing Internet standards in which case the AUTHINFO
              GENERIC extension
        Rich Salz-Original author of INN
        Henry Spencer-One of procedures for
   copyrights defined in the original authors of CNEWS
        Kim Storm-Original author of Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the NN news reader

  Feather                                                [Page 67] Internet Society or its successors or assignees.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET DRAFT                                         C. Feather
  Expires: July 31, 2003                                   Thus plc
                                                       January 2003

     The present author gratefully acknowledges SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

   Funding for the vast amount of
     work put into previous drafts RFC Editor function is currently provided by the original author:
        Stan Barber <sob@academ.com>

  18  Author's Address

  Clive Feather
  Thus plc
  322 Regents Park Road
  London
  N3  2QQ
  United Kingdom

  Email: clive@demon.net
     or: clive@davros.org
  Tel: +44 20 8371 1138

  This memo expires July 31, 2003.
   Internet Society.