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rfc:rfc977

Network Working Group Brian Kantor (U.C. San Diego) Request for Comments: 977 Phil Lapsley (U.C. Berkeley)

                                                         February 1986
                   Network News Transfer Protocol
                                  
              A Proposed Standard for the Stream-Based
                        Transmission of News

Status of This Memo

 NNTP specifies a protocol for the distribution, inquiry, retrieval,
 and posting of news articles using a reliable stream-based
 transmission of news among the ARPA-Internet community.  NNTP is
 designed so that news articles are stored in a central database
 allowing a subscriber to select only those items he wishes to read.
 Indexing, cross-referencing, and expiration of aged messages are also
 provided. This RFC suggests a proposed protocol for the ARPA-Internet
 community, and requests discussion and suggestions for improvements.
 Distribution of this memo is unlimited.

1. Introduction

 For many years, the ARPA-Internet community has supported the
 distribution of bulletins, information, and data in a timely fashion
 to thousands of participants.  We collectively refer to such items of
 information as "news".  Such news provides for the rapid
 dissemination of items of interest such as software bug fixes, new
 product reviews, technical tips, and programming pointers, as well as
 rapid-fire discussions of matters of concern to the working computer
 professional. News is very popular among its readers.
 There are popularly two methods of distributing such news: the
 Internet method of direct mailing, and the USENET news system.

1.1. Internet Mailing Lists

 The Internet community distributes news by the use of mailing lists.
 These are lists of subscriber's mailbox addresses and remailing
 sublists of all intended recipients.  These mailing lists operate by
 remailing a copy of the information to be distributed to each
 subscriber on the mailing list.  Such remailing is inefficient when a
 mailing list grows beyond a dozen or so people, since sending a
 separate copy to each of the subscribers occupies large quantities of
 network bandwidth, CPU resources, and significant amounts of disk
 storage at the destination host.  There is also a significant problem
 in maintenance of the list itself: as subscribers move from one job
 to another; as new subscribers join and old ones leave; and as hosts
 come in and out of service.

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RFC 977 February 1986 Network News Transfer Protocol

1.2. The USENET News System

 Clearly, a worthwhile reduction of the amount of these resources used
 can be achieved if articles are stored in a central database on the
 receiving host instead of in each subscriber's mailbox. The USENET
 news system provides a method of doing just this.  There is a central
 repository of the news articles in one place (customarily a spool
 directory of some sort), and a set of programs that allow a
 subscriber to select those items he wishes to read.  Indexing,
 cross-referencing, and expiration of aged messages are also provided.

1.3. Central Storage of News

 For clusters of hosts connected together by fast local area networks
 (such as Ethernet), it makes even more sense to consolidate news
 distribution onto one (or a very few) hosts, and to allow access to
 these news articles using a server and client model.  Subscribers may
 then request only the articles they wish to see, without having to
 wastefully duplicate the storage of a copy of each item on each host.

1.4. A Central News Server

 A way to achieve these economies is to have a central computer system
 that can provide news service to the other systems on the local area
 network.  Such a server would manage the collection of news articles
 and index files, with each person who desires to read news bulletins
 doing so over the LAN.  For a large cluster of computer systems, the
 savings in total disk space is clearly worthwhile.  Also, this allows
 workstations with limited disk storage space to participate in the
 news without incoming items consuming oppressive amounts of the
 workstation's disk storage.
 We have heard rumors of somewhat successful attempts to provide
 centralized news service using IBIS and other shared or distributed
 file systems.  While it is possible that such a distributed file
 system implementation might work well with a group of similar
 computers running nearly identical operating systems, such a scheme
 is not general enough to offer service to a wide range of client
 systems, especially when many diverse operating systems may be in use
 among a group of clients.  There are few (if any) shared or networked
 file systems that can offer the generality of service that stream
 connections using Internet TCP provide, particularly when a wide
 range of host hardware and operating systems are considered.
 NNTP specifies a protocol for the distribution, inquiry, retrieval,
 and posting of news articles using a reliable stream (such as TCP)
 server-client model. NNTP is designed so that news articles need only

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RFC 977 February 1986 Network News Transfer Protocol

 be stored on one (presumably central) host, and subscribers on other
 hosts attached to the LAN may read news articles using stream
 connections to the news host.
 NNTP is modelled upon the news article specifications in RFC 850,
 which describes the USENET news system.  However, NNTP makes few
 demands upon the structure, content, or storage of news articles, and
 thus we believe it easily can be adapted to other non-USENET news
 systems.
 Typically, the NNTP server runs as a background process on one host,
 and would accept connections from other hosts on the LAN.  This works
 well when there are a number of small computer systems (such as
 workstations, with only one or at most a few users each), and a large
 central server.

1.5. Intermediate News Servers

 For clusters of machines with many users (as might be the case in a
 university or large industrial environment), an intermediate server
 might be used.  This intermediate or "slave" server runs on each
 computer system, and is responsible for mediating news reading
 requests and performing local caching of recently-retrieved news
 articles.
 Typically, a client attempting to obtain news service would first
 attempt to connect to the news service port on the local machine.  If
 this attempt were unsuccessful, indicating a failed server, an
 installation might choose to either deny news access, or to permit
 connection to the central "master" news server.
 For workstations or other small systems, direct connection to the
 master server would probably be the normal manner of operation.
 This specification does not cover the operation of slave NNTP
 servers.  We merely suggest that slave servers are a logical addition
 to NNTP server usage which would enhance operation on large local
 area networks.

1.6. News Distribution

 NNTP has commands which provide a straightforward method of
 exchanging articles between cooperating hosts. Hosts which are well
 connected on a local area or other fast network and who wish to
 actually obtain copies of news articles for local storage might well
 find NNTP to be a more efficient way to distribute news than more
 traditional transfer methods (such as UUCP).

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RFC 977 February 1986 Network News Transfer Protocol

 In the traditional method of distributing news articles, news is
 propagated from host to host by flooding - that is, each host will
 send all its new news articles on to each host that it feeds.  These
 hosts will then in turn send these new articles on to other hosts
 that they feed.  Clearly, sending articles that a host already has
 obtained a copy of from another feed (many hosts that receive news
 are redundantly fed) again is a waste of time and communications
 resources, but for transport mechanisms that are single-transaction
 based rather than interactive (such as UUCP in the UNIX-world <1>),
 distribution time is diminished by sending all articles and having
 the receiving host simply discard the duplicates.  This is an
 especially true when communications sessions are limited to once a
 day.
 Using NNTP, hosts exchanging news articles have an interactive
 mechanism for deciding which articles are to be transmitted.  A host
 desiring new news, or which has new news to send, will typically
 contact one or more of its neighbors using NNTP.  First it will
 inquire if any new news groups have been created on the serving host
 by means of the NEWGROUPS command.  If so, and those are appropriate
 or desired (as established by local site-dependent rules), those new
 newsgroups can be created.
 The client host will then inquire as to which new articles have
 arrived in all or some of the newsgroups that it desires to receive,
 using the NEWNEWS command.  It will receive a list of new articles
 from the server, and can request transmission of those articles that
 it desires and does not already have.
 Finally, the client can advise the server of those new articles which
 the client has recently received.  The server will indicate those
 articles that it has already obtained copies of, and which articles
 should be sent to add to its collection.
 In this manner, only those articles which are not duplicates and
 which are desired are transferred.

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RFC 977 February 1986 Network News Transfer Protocol

2. The NNTP Specification

2.1. Overview

 The news server specified by this document uses a stream connection
 (such as TCP) and SMTP-like commands and responses.  It is designed
 to accept connections from hosts, and to provide a simple interface
 to the news database.
 This server is only an interface between programs and the news
 databases. It does not perform any user interaction or presentation-
 level functions. These "user-friendly" functions are better left to
 the client programs, which have a better understanding of the
 environment in which they are operating.
 When used via Internet TCP, the contact port assigned for this
 service is 119.

2.2. Character Codes

 Commands and replies are composed of characters from the ASCII
 character set.  When the transport service provides an 8-bit byte
 (octet) transmission channel, each 7-bit character is transmitted
 right justified in an octet with the high order bit cleared to zero.

2.3. Commands

 Commands consist of a command word, which in some cases may be
 followed by a parameter.  Commands with parameters must separate the
 parameters from each other and from the command by one or more space
 or tab characters.  Command lines must be complete with all required
 parameters, and may not contain more than one command.
 Commands and command parameters are not case sensitive. That is, a
 command or parameter word may be upper case, lower case, or any
 mixture of upper and lower case.
 Each command line must be terminated by a CR-LF (Carriage Return -
 Line Feed) pair.
 Command lines shall not exceed 512 characters in length, counting all
 characters including spaces, separators, punctuation, and the
 trailing CR-LF (thus there are 510 characters maximum allowed for the
 command and its parameters).  There is no provision for continuation
 command lines.

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RFC 977 February 1986 Network News Transfer Protocol

2.4. Responses

 Responses are of two kinds, textual and status.

2.4.1. Text Responses

 Text is sent only after a numeric status response line has been sent
 that indicates that text will follow.  Text is sent as a series of
 successive lines of textual matter, each terminated with CR-LF pair.
 A single line containing only a period (.) is sent to indicate the
 end of the text (i.e., the server will send a CR-LF pair at the end
 of the last line of text, a period, and another CR-LF pair).
 If the text contained a period as the first character of the text
 line in the original, that first period is doubled.  Therefore, the
 client must examine the first character of each line received, and
 for those beginning with a period, determine either that this is the
 end of the text or whether to collapse the doubled period to a single
 one.
 The intention is that text messages will usually be displayed on the
 user's terminal whereas command/status responses will be interpreted
 by the client program before any possible display is done.

2.4.2. Status Responses

 These are status reports from the server and indicate the response to
 the last command received from the client.
 Status response lines begin with a 3 digit numeric code which is
 sufficient to distinguish all responses.  Some of these may herald
 the subsequent transmission of text.
 The first digit of the response broadly indicates the success,
 failure, or progress of the previous command.
    1xx - Informative message
    2xx - Command ok
    3xx - Command ok so 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.

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RFC 977 February 1986 Network News Transfer Protocol

 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 - Nonstandard (private implementation) extensions
    x9x - Debugging output
 The exact response codes that should be expected from each command
 are detailed in the description of that command.  In addition, below
 is listed a general set of response codes that may be received at any
 time.
 Certain status responses contain parameters such as numbers and
 names. The number and type of such parameters is fixed for each
 response code to simplify interpretation of the response.
 Parameters are separated from the numeric response code and from each
 other by a single space. All numeric parameters are decimal, and may
 have leading zeros. All string parameters begin after the separating
 space, and end before the following separating space or the CR-LF
 pair at the end of the line. (String parameters may not, therefore,
 contain spaces.) All text, if any, in the response which is not a
 parameter of the response must follow and be separated from the last
 parameter by a space.  Also, note that the text following a response
 number may vary in different implementations of the server. The
 3-digit numeric code should be used to determine what response was
 sent.
 Response codes not specified in this standard may be used for any
 installation-specific additional commands also not specified. These
 should be chosen to fit the pattern of x8x specified above.  (Note
 that debugging is provided for explicitly in the x9x response codes.)
 The use of unspecified response codes for standard commands is
 prohibited.
 We have provided a response pattern x9x for debugging.  Since much
 debugging output may be classed as "informative messages", we would
 expect, therefore, that responses 190 through 199 would be used for
 various debugging outputs.  There is no requirement in this
 specification for debugging output, but if such is provided over the
 connected stream, it must use these response codes.  If appropriate
 to a specific implementation, other x9x codes may be used for
 debugging.  (An example might be to use e.g., 290 to acknowledge a
 remote debugging request.)

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RFC 977 February 1986 Network News Transfer Protocol

2.4.3. General Responses

 The following is a list of general response codes that may be sent by
 the NNTP server.  These are not specific to any one command, but may
 be returned as the result of a connection, a failure, or some unusual
 condition.
 In general, 1xx codes may be ignored or displayed as desired;  code
 200 or 201 is sent upon initial connection to the NNTP server
 depending upon posting permission; code 400 will be sent when the
 NNTP server discontinues service (by operator request, for example);
 and 5xx codes indicate that the command could not be performed for
 some unusual reason.
    100 help text
    190
      through
    199 debug output
    200 server ready - posting allowed
    201 server ready - no posting allowed
    400 service discontinued
    500 command not recognized
    501 command syntax error
    502 access restriction or permission denied
    503 program fault - command not performed

3. Command and Response Details

 On the following pages are descriptions of each command recognized by
 the NNTP server and the responses which will be returned by those
 commands.
 Each command is shown in upper case for clarity, although case is
 ignored in the interpretation of commands by the NNTP server.  Any
 parameters are shown in lower case.  A parameter shown in [square
 brackets] is optional.  For example, [GMT] indicates that the
 triglyph GMT may present or omitted.
 Every command described in this section must be implemented by all
 NNTP servers.

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RFC 977 February 1986 Network News Transfer Protocol

 There is no prohibition against additional commands being added;
 however, it is recommended that any such unspecified command begin
 with the letter "X" to avoid conflict with later revisions of this
 specification.
 Implementors are reminded that such additional commands may not
 redefine specified status response codes.  Using additional
 unspecified responses for standard commands is also prohibited.

3.1. The ARTICLE, BODY, HEAD, and STAT commands

 There are two forms to the ARTICLE command (and the related BODY,
 HEAD, and STAT commands), each using a different method of specifying
 which article is to be retrieved.  When the ARTICLE command is
 followed by a message-id in angle brackets ("<" and ">"), the first
 form of the command is used; when a numeric parameter or no parameter
 is supplied, the second form is invoked.
 The text of the article is returned as a textual response, as
 described earlier in this document.
 The HEAD and BODY commands are identical to the ARTICLE command
 except that they respectively return only the header lines or text
 body of the article.
 The STAT command is similar to the ARTICLE command except that no
 text is returned.  When selecting by message number within a group,
 the STAT command serves to set the current article pointer without
 sending text. The returned acknowledgement response will contain the
 message-id, which may be of some value.  Using the STAT command to
 select by message-id is valid but of questionable value, since a
 selection by message-id does NOT alter the "current article pointer".

3.1.1. ARTICLE (selection by message-id)

 ARTICLE <message-id>
 Display the header, a blank line, then the body (text) of the
 specified article.  Message-id is the message id of an article as
 shown in that article's header.  It is anticipated that the client
 will obtain the message-id from a list provided by the NEWNEWS
 command, from references contained within another article, or from
 the message-id provided in the response to some other commands.
 Please note that the internally-maintained "current article pointer"
 is NOT ALTERED by this command. This is both to facilitate the
 presentation of articles that may be referenced within an article

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RFC 977 February 1986 Network News Transfer Protocol

 being read, and because of the semantic difficulties of determining
 the proper sequence and membership of an article which may have been
 posted to more than one newsgroup.

3.1.2. ARTICLE (selection by number)

 ARTICLE [nnn]
 Displays the header, a blank line, then the body (text) of the
 current or specified article.  The optional parameter nnn is the
 numeric id of an article in the current newsgroup and must be chosen
 from the range of articles provided when the newsgroup was selected.
 If it is omitted, the current article is assumed.
 The internally-maintained "current article pointer" is set by this
 command if a valid article number is specified.
 [the following applies to both forms of the article command.] A
 response indicating the current article number, a message-id string,
 and that text is to follow will be returned.
 The message-id string returned is an identification string contained
 within angle brackets ("<" and ">"), which is derived from the header
 of the article itself.  The Message-ID header line (required by
 RFC850) from the article must be used to supply this information. If
 the message-id header line is missing from the article, a single
 digit "0" (zero) should be supplied within the angle brackets.
 Since the message-id field is unique with each article, it may be
 used by a news reading program to skip duplicate displays of articles
 that have been posted more than once, or to more than one newsgroup.

3.1.3. Responses

 220 n <a> article retrieved - head and body follow
         (n = article number, <a> = message-id)
 221 n <a> article retrieved - head follows
 222 n <a> article retrieved - body follows
 223 n <a> article retrieved - request text separately
 412 no newsgroup has been selected
 420 no current article has been selected
 423 no such article number in this group
 430 no such article found

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RFC 977 February 1986 Network News Transfer Protocol

3.2. The GROUP command

3.2.1. GROUP

 GROUP ggg
 The required parameter ggg is the name of the newsgroup to be
 selected (e.g. "net.news").  A list of valid newsgroups may be
 obtained from the LIST command.
 The successful selection response will return the article numbers of
 the first and last articles in the group, and an estimate of the
 number of articles on file in the group.  It is not necessary that
 the estimate be correct, although that is helpful; it must only be
 equal to or larger than the actual number of articles on file.  (Some
 implementations will actually count the number of articles on file.
 Others will just subtract first article number from last to get an
 estimate.)
 When a valid group is selected by means of this command, the
 internally maintained "current article pointer" is set to the first
 article in the group.  If an invalid group is specified, the
 previously selected group and article remain selected.  If an empty
 newsgroup is selected, the "current article pointer" is in an
 indeterminate state and should not be used.
 Note that the name of the newsgroup is not case-dependent.  It must
 otherwise match a newsgroup obtained from the LIST command or an
 error will result.

3.2.2. Responses

 211 n f l s group selected
         (n = estimated number of articles in group,
         f = first article number in the group,
         l = last article number in the group,
         s = name of the group.)
 411 no such news group

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RFC 977 February 1986 Network News Transfer Protocol

3.3. The HELP command

3.3.1. HELP

 HELP
 Provides a short summary of commands that are understood by this
 implementation of the server. The help text will be presented as a
 textual response, terminated by a single period on a line by itself.
 3.3.2.  Responses
 100 help text follows

3.4. The IHAVE command

3.4.1. IHAVE

 IHAVE <messageid>
 The IHAVE command informs the server that the client has an article
 whose id is <messageid>.  If the server desires a copy of that
 article, it will return a response instructing the client to send the
 entire article.  If the server does not want the article (if, for
 example, the server already has a copy of it), a response indicating
 that the article is not wanted will be returned.
 If transmission of the article is requested, the client should send
 the entire article, including header and body, in the manner
 specified for text transmission from the server. A response code
 indicating success or failure of the transferral of the article will
 be returned.
 This function differs from the POST command in that it is intended
 for use in transferring already-posted articles between hosts.
 Normally it will not be used when the client is a personal
 newsreading program.  In particular, this function will invoke the
 server's news posting program with the appropriate settings (flags,
 options, etc) to indicate that the forthcoming article is being
 forwarded from another host.
 The server may, however, elect not to post or forward the article if
 after further examination of the article it deems it inappropriate to
 do so.  The 436 or 437 error codes may be returned as appropriate to
 the situation.
 Reasons for such subsequent rejection of an article may include such

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RFC 977 February 1986 Network News Transfer Protocol

 problems as inappropriate newsgroups or distributions, disk space
 limitations, article lengths, garbled headers, and the like.  These
 are typically restrictions enforced by the server host's news
 software and not necessarily the NNTP server itself.

3.4.2. Responses

 235 article transferred ok
 335 send article to be transferred.  End with <CR-LF>.<CR-LF>
 435 article not wanted - do not send it
 436 transfer failed - try again later
 437 article rejected - do not try again
 An implementation note:
 Because some host news posting software may not be able to decide
 immediately that an article is inappropriate for posting or
 forwarding, it is acceptable to acknowledge the successful transfer
 of the article and to later silently discard it.  Thus it is
 permitted to return the 235 acknowledgement code and later discard
 the received article.  This is not a fully satisfactory solution to
 the problem.  Perhaps some implementations will wish to send mail to
 the author of the article in certain of these cases.

3.5. The LAST command

3.5.1. LAST

 LAST
 The internally maintained "current article pointer" is set to the
 previous article in the current newsgroup.  If already positioned at
 the first article of the newsgroup, an error message is returned and
 the current article remains selected.
 The internally-maintained "current article pointer" is set by this
 command.
 A response indicating the current article number, and a message-id
 string will be returned.  No text is sent in response to this
 command.

3.5.2. Responses

 223 n a article retrieved - request text separately
         (n = article number, a = unique article id)

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RFC 977 February 1986 Network News Transfer Protocol

 412 no newsgroup selected
 420 no current article has been selected
 422 no previous article in this group

3.6. The LIST command

3.6.1. LIST

 LIST
 Returns a list of valid newsgroups and associated information.  Each
 newsgroup is sent as a line of text in the following format:
    group last first p
 where <group> is the name of the newsgroup, <last> is the number of
 the last known article currently in that newsgroup, <first> is the
 number of the first article currently in the newsgroup, and <p> is
 either 'y' or 'n' indicating whether posting to this newsgroup is
 allowed ('y') or prohibited ('n').
 The <first> and <last> fields will always be numeric.  They may have
 leading zeros.  If the <last> field evaluates to less than the
 <first> field, there are no articles currently on file in the
 newsgroup.
 Note that posting may still be prohibited to a client even though the
 LIST command indicates that posting is permitted to a particular
 newsgroup. See the POST command for an explanation of client
 prohibitions.  The posting flag exists for each newsgroup because
 some newsgroups are moderated or are digests, and therefore cannot be
 posted to; that is, articles posted to them must be mailed to a
 moderator who will post them for the submitter.  This is independent
 of the posting permission granted to a client by the NNTP server.
 Please note that an empty list (i.e., the text body returned by this
 command consists only of the terminating period) is a possible valid
 response, and indicates that there are currently no valid newsgroups.

3.6.2. Responses

 215 list of newsgroups follows

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RFC 977 February 1986 Network News Transfer Protocol

3.7. The NEWGROUPS command

3.7.1. NEWGROUPS

 NEWGROUPS date time [GMT] [<distributions>]
 A list of newsgroups created since <date and time> will be listed in
 the same format as the LIST command.
 The date is sent as 6 digits in the format YYMMDD, where YY is the
 last two digits of the year, MM is the two digits of the month (with
 leading zero, if appropriate), and DD is the day of the month (with
 leading zero, if appropriate).  The closest century is assumed as
 part of the year (i.e., 86 specifies 1986, 30 specifies 2030, 99 is
 1999, 00 is 2000).
 Time must also be specified.  It must be as 6 digits HHMMSS with HH
 being hours on the 24-hour clock, MM minutes 00-59, and SS seconds
 00-59.  The time is assumed to be in the server's timezone unless the
 token "GMT" appears, in which case both time and date are evaluated
 at the 0 meridian.
 The optional parameter "distributions" is a list of distribution
 groups, enclosed in angle brackets.  If specified, the distribution
 portion of a new newsgroup (e.g, 'net' in 'net.wombat') will be
 examined for a match with the distribution categories listed, and
 only those new newsgroups which match will be listed.  If more than
 one distribution group is to be listed, they must be separated by
 commas within the angle brackets.
 Please note that an empty list (i.e., the text body returned by this
 command consists only of the terminating period) is a possible valid
 response, and indicates that there are currently no new newsgroups.

3.7.2. Responses

 231 list of new newsgroups follows

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RFC 977 February 1986 Network News Transfer Protocol

3.8. The NEWNEWS command

3.8.1. NEWNEWS

 NEWNEWS newsgroups date time [GMT] [<distribution>]
 A list of message-ids of articles posted or received to the specified
 newsgroup since "date" will be listed. The format of the listing will
 be one message-id per line, as though text were being sent.  A single
 line consisting solely of one period followed by CR-LF will terminate
 the list.
 Date and time are in the same format as the NEWGROUPS command.
 A newsgroup name containing a "*" (an asterisk) may be specified to
 broaden the article search to some or all newsgroups.  The asterisk
 will be extended to match any part of a newsgroup name (e.g.,
 net.micro* will match net.micro.wombat, net.micro.apple, etc). Thus
 if only an asterisk is given as the newsgroup name, all newsgroups
 will be searched for new news.
 (Please note that the asterisk "*" expansion is a general
 replacement; in particular, the specification of e.g., net.*.unix
 should be correctly expanded to embrace names such as net.wombat.unix
 and net.whocares.unix.)
 Conversely, if no asterisk appears in a given newsgroup name, only
 the specified newsgroup will be searched for new articles. Newsgroup
 names must be chosen from those returned in the listing of available
 groups.  Multiple newsgroup names (including a "*") may be specified
 in this command, separated by a comma.  No comma shall appear after
 the last newsgroup in the list.  [Implementors are cautioned to keep
 the 512 character command length limit in mind.]
 The exclamation point ("!") may be used to negate a match. This can
 be used to selectively omit certain newsgroups from an otherwise
 larger list.  For example, a newsgroups specification of
 "net.*,mod.*,!mod.map.*" would specify that all net.<anything> and
 all mod.<anything> EXCEPT mod.map.<anything> newsgroup names would be
 matched.  If used, the exclamation point must appear as the first
 character of the given newsgroup name or pattern.
 The optional parameter "distributions" is a list of distribution
 groups, enclosed in angle brackets.  If specified, the distribution
 portion of an article's newsgroup (e.g, 'net' in 'net.wombat') will
 be examined for a match with the distribution categories listed, and
 only those articles which have at least one newsgroup belonging to

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RFC 977 February 1986 Network News Transfer Protocol

 the list of distributions will be listed.  If more than one
 distribution group is to be supplied, they must be separated by
 commas within the angle brackets.
 The use of the IHAVE, NEWNEWS, and NEWGROUPS commands to distribute
 news is discussed in an earlier part of this document.
 Please note that an empty list (i.e., the text body returned by this
 command consists only of the terminating period) is a possible valid
 response, and indicates that there is currently no new news.

3.8.2. Responses

 230 list of new articles by message-id follows

3.9. The NEXT command

3.9.1. NEXT

 NEXT
 The internally maintained "current article pointer" is advanced to
 the next article in the current newsgroup.  If no more articles
 remain in the current group, an error message is returned and the
 current article remains selected.
 The internally-maintained "current article pointer" is set by this
 command.
 A response indicating the current article number, and the message-id
 string will be returned.  No text is sent in response to this
 command.

3.9.2. Responses

 223 n a article retrieved - request text separately
         (n = article number, a = unique article id)
 412 no newsgroup selected
 420 no current article has been selected
 421 no next article in this group

Kantor & Lapsley [Page 17]

RFC 977 February 1986 Network News Transfer Protocol

3.10. The POST command

3.10.1. POST

 POST
 If posting is allowed, response code 340 is returned to indicate that
 the article to be posted should be sent. Response code 440 indicates
 that posting is prohibited for some installation-dependent reason.
 If posting is permitted, the article should be presented in the
 format specified by RFC850, and should include all required header
 lines. After the article's header and body have been completely sent
 by the client to the server, a further response code will be returned
 to indicate success or failure of the posting attempt.
 The text forming the header and body of the message to be posted
 should be sent by the client using the conventions for text received
 from the news server:  A single period (".") on a line indicates the
 end of the text, with lines starting with a period in the original
 text having that period doubled during transmission.
 No attempt shall be made by the server to filter characters, fold or
 limit lines, or otherwise process incoming text.  It is our intent
 that the server just pass the incoming message to be posted to the
 server installation's news posting software, which is separate from
 this specification.  See RFC850 for more details.
 Since most installations will want the client news program to allow
 the user to prepare his message using some sort of text editor, and
 transmit it to the server for posting only after it is composed, the
 client program should take note of the herald message that greeted it
 when the connection was first established. This message indicates
 whether postings from that client are permitted or not, and can be
 used to caution the user that his access is read-only if that is the
 case. This will prevent the user from wasting a good deal of time
 composing a message only to find posting of the message was denied.
 The method and determination of which clients and hosts may post is
 installation dependent and is not covered by this specification.

3.10.2. Responses

 240 article posted ok
 340 send article to be posted. End with <CR-LF>.<CR-LF>
 440 posting not allowed
 441 posting failed

Kantor & Lapsley [Page 18]

RFC 977 February 1986 Network News Transfer Protocol

 (for reference, one of the following codes will be sent upon initial
 connection; the client program should determine whether posting is
 generally permitted from these:) 200 server ready - posting allowed
 201 server ready - no posting allowed

3.11. The QUIT command

3.11.1. QUIT

 QUIT
 The server process acknowledges the QUIT command and then closes the
 connection to the client.  This is the preferred method for a client
 to indicate 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 should gracefully cease its attempts
 to service the client.

3.11.2. Responses

 205 closing connection - goodbye!

3.12. The SLAVE command

3.12.1. SLAVE

 SLAVE
 Indicates to the server that this client connection is to a slave
 server, rather than a user.
 This command is intended for use in separating connections to single
 users from those to subsidiary ("slave") servers.  It may be used to
 indicate that priority should therefore be given to requests from
 this client, as it is presumably serving more than one person.  It
 might also be used to determine which connections to close when
 system load levels are exceeded, perhaps giving preference to slave
 servers.  The actual use this command is put to is entirely
 implementation dependent, and may vary from one host to another.  In
 NNTP servers which do not give priority to slave servers, this
 command must nonetheless be recognized and acknowledged.

3.12.2. Responses

 202 slave status noted

Kantor & Lapsley [Page 19]

RFC 977 February 1986 Network News Transfer Protocol

4. Sample Conversations

 These are samples of the conversations that might be expected with
 the news server in hypothetical sessions.  The notation C: indicates
 commands sent to the news server from the client program; S: indicate
 responses received from the server by the client.

4.1. Example 1 - relative access with NEXT

 S:      (listens at TCP port 119)
 C:      (requests connection on TCP port 119)
 S:      200 wombatvax news server ready - posting ok
 (client asks for a current newsgroup list)
 C:      LIST
 S:      215 list of newsgroups follows
 S:      net.wombats 00543 00501 y
 S:      net.unix-wizards 10125 10011 y
         (more information here)
 S:      net.idiots 00100 00001 n
 S:      .
 (client selects a newsgroup)
 C:      GROUP net.unix-wizards
 S:      211 104 10011 10125 net.unix-wizards group selected
         (there are 104 articles on file, from 10011 to 10125)
 (client selects an article to read)
 C:      STAT 10110
 S:      223 10110 <23445@sdcsvax.ARPA> article retrieved - statistics
         only (article 10110 selected, its message-id is
         <23445@sdcsvax.ARPA>)
 (client examines the header)
 C:      HEAD
 S:      221 10110 <23445@sdcsvax.ARPA> article retrieved - head
         follows (text of the header appears here)
 S:      .
 (client wants to see the text body of the article)
 C:      BODY
 S:      222 10110 <23445@sdcsvax.ARPA> article retrieved - body
         follows (body text here)
 S:      .
 (client selects next article in group)

Kantor & Lapsley [Page 20]

RFC 977 February 1986 Network News Transfer Protocol

 C:      NEXT
 S:      223 10113 <21495@nudebch.uucp> article retrieved - statistics
         only (article 10113 was next in group)
 (client finishes session)
 C:      QUIT
 S:      205 goodbye.

4.2. Example 2 - absolute article access with ARTICLE

 S:      (listens at TCP port 119)
 C:      (requests connection on TCP port 119)
 S:      201 UCB-VAX netnews server ready -- no posting allowed
 C:      GROUP msgs
 S:      211 103 402 504 msgs Your new group is msgs
         (there are 103 articles, from 402 to 504)
 C:      ARTICLE 401
 S:      423 No such article in this newsgroup
 C:      ARTICLE 402
 S:      220 402 <4105@ucbvax.ARPA> Article retrieved, text follows
 S:      (article header and body follow)
 S:      .
 C:      HEAD 403
 S:      221 403 <3108@mcvax.UUCP> Article retrieved, header follows
 S:      (article header follows)
 S:      .
 C:      QUIT
 S:      205 UCB-VAX news server closing connection.  Goodbye.

4.3. Example 3 - NEWGROUPS command

 S:      (listens at TCP port 119)
 C:      (requests connection on TCP port 119)
 S:      200 Imaginary Institute News Server ready (posting ok)
 (client asks for new newsgroups since April 3, 1985)
 C:      NEWGROUPS 850403 020000
 S:      231 New newsgroups since 03/04/85 02:00:00 follow

Kantor & Lapsley [Page 21]

RFC 977 February 1986 Network News Transfer Protocol

 S:      net.music.gdead
 S:      net.games.sources
 S:      .
 C:      GROUP net.music.gdead
 S:      211 0 1 1 net.music.gdead Newsgroup selected
         (there are no articles in that newsgroup, and
         the first and last article numbers should be ignored)
 C:      QUIT
 S:      205 Imaginary Institute news server ceasing service.  Bye!

4.4. Example 4 - posting a news article

 S:      (listens at TCP port 119)
 C:      (requests connection on TCP port 119)
 S:      200 BANZAIVAX news server ready, posting allowed.
 C:      POST
 S:      340 Continue posting; Period on a line by itself to end
 C:      (transmits news article in RFC850 format)
 C:      .
 S:      240 Article posted successfully.
 C:      QUIT
 S:      205 BANZAIVAX closing connection.  Goodbye.

4.5. Example 5 - interruption due to operator request

 S:      (listens at TCP port 119)
 C:      (requests connection on TCP port 119)
 S:      201 genericvax news server ready, no posting allowed.
         (assume normal conversation for some time, and
         that a newsgroup has been selected)
 C:      NEXT
 S:      223 1013 <5734@mcvax.UUCP> Article retrieved; text separate.
 C:      HEAD
 C:      221 1013 <5734@mcvax.UUCP> Article retrieved; head follows.
 S:      (sends head of article, but halfway through is
         interrupted by an operator request.  The following
         then occurs, without client intervention.)

Kantor & Lapsley [Page 22]

RFC 977 February 1986 Network News Transfer Protocol

 S:      (ends current line with a CR-LF pair)
 S:      .
 S:      400 Connection closed by operator.  Goodbye.
 S:      (closes connection)

4.6. Example 6 - Using the news server to distribute news between

    systems.
 S:      (listens at TCP port 119)
 C:      (requests connection on TCP port 119)
 S:      201 Foobar NNTP server ready (no posting)
 (client asks for new newsgroups since 2 am, May 15, 1985)
 C:      NEWGROUPS 850515 020000
 S:      235 New newsgroups since 850515 follow
 S:      net.fluff
 S:      net.lint
 S:      .
 (client asks for new news articles since 2 am, May 15, 1985)
 C:      NEWNEWS * 850515 020000
 S:      230 New news since 850515 020000 follows
 S:      <1772@foo.UUCP>
 S:      <87623@baz.UUCP>
 S:      <17872@GOLD.CSNET>
 S:      .
 (client asks for article <1772@foo.UUCP>)
 C:      ARTICLE <1772@foo.UUCP>
 S:      220 <1772@foo.UUCP> All of article follows
 S:      (sends entire message)
 S:      .
 (client asks for article <87623@baz.UUCP>
 C:      ARTICLE <87623@baz.UUCP>
 S:      220 <87623@baz.UUCP> All of article follows
 S:      (sends entire message)
 S:      .
 (client asks for article <17872@GOLD.CSNET>
 C:      ARTICLE <17872@GOLD.CSNET>
 S:      220 <17872@GOLD.CSNET> All of article follows
 S:      (sends entire message)
 S:      .

Kantor & Lapsley [Page 23]

RFC 977 February 1986 Network News Transfer Protocol

 (client offers an article it has received recently)
 C:      IHAVE <4105@ucbvax.ARPA>
 S:      435 Already seen that one, where you been?
 (client offers another article)
 C:      IHAVE <4106@ucbvax.ARPA>
 S:      335 News to me!  <CRLF.CRLF> to end.
 C:      (sends article)
 C:      .
 S:      235 Article transferred successfully.  Thanks.
 (or)
 S:      436 Transfer failed.
 (client is all through with the session)
 C:      QUIT
 S:      205 Foobar NNTP server bids you farewell.

4.7. Summary of commands and responses.

 The following are the commands recognized and responses returned by
 the NNTP server.

4.7.1. Commands

 ARTICLE
 BODY
 GROUP
 HEAD
 HELP
 IHAVE
 LAST
 LIST
 NEWGROUPS
 NEWNEWS
 NEXT
 POST
 QUIT
 SLAVE
 STAT

4.7.2. Responses

 100 help text follows
 199 debug output

Kantor & Lapsley [Page 24]

RFC 977 February 1986 Network News Transfer Protocol

 200 server ready - posting allowed
 201 server ready - no posting allowed
 202 slave status noted
 205 closing connection - goodbye!
 211 n f l s group selected
 215 list of newsgroups follows
 220 n <a> article retrieved - head and body follow 221 n <a> article
 retrieved - head follows
 222 n <a> article retrieved - body follows
 223 n <a> article retrieved - request text separately 230 list of new
 articles by message-id follows
 231 list of new newsgroups follows
 235 article transferred ok
 240 article posted ok
 335 send article to be transferred.  End with <CR-LF>.<CR-LF>
 340 send article to be posted. End with <CR-LF>.<CR-LF>
 400 service discontinued
 411 no such news group
 412 no newsgroup has been selected
 420 no current article has been selected
 421 no next article in this group
 422 no previous article in this group
 423 no such article number in this group
 430 no such article found
 435 article not wanted - do not send it
 436 transfer failed - try again later
 437 article rejected - do not try again.
 440 posting not allowed
 441 posting failed
 500 command not recognized
 501 command syntax error
 502 access restriction or permission denied
 503 program fault - command not performed

4.8. A Brief Word about the USENET News System

 In the UNIX world, which traditionally has been linked by 1200 baud
 dial-up telephone lines, the USENET News system has evolved to handle
 central storage, indexing, retrieval, and distribution of news.  With
 the exception of its underlying transport mechanism (UUCP), USENET
 News is an efficient means of providing news and bulletin service to
 subscribers on UNIX and other hosts worldwide.  The USENET News

Kantor & Lapsley [Page 25]

RFC 977 February 1986 Network News Transfer Protocol

 system is discussed in detail in RFC 850.  It runs on most versions
 of UNIX and on many other operating systems, and is customarily
 distributed without charge.
 USENET uses a spooling area on the UNIX host to store news articles,
 one per file. Each article consists of a series of heading text,
 which contain the sender's identification and organizational
 affiliation, timestamps, electronic mail reply paths, subject,
 newsgroup (subject category), and the like.  A complete news article
 is reproduced in its entirety below.  Please consult RFC 850 for more
 details.
    Relay-Version: version B 2.10.3 4.3bsd-beta 6/6/85; site
    sdcsvax.UUCP
    Posting-Version: version B 2.10.1 6/24/83 SMI; site unitek.uucp
    Path:sdcsvax!sdcrdcf!hplabs!qantel!ihnp4!alberta!ubc-vision!unitek
    !honman
    From: honman@unitek.uucp (Man Wong)
    Newsgroups: net.unix-wizards
    Subject: foreground -> background ?
    Message-ID: <167@unitek.uucp>
    Date: 25 Sep 85 23:51:52 GMT
    Date-Received: 29 Sep 85 09:54:48 GMT
    Reply-To: honman@unitek.UUCP (Hon-Man Wong)
    Distribution: net.all
    Organization: Unitek Technologies Corporation
    Lines: 12
    I have a process (C program) which generates a child and waits for
    it to return.  What I would like to do is to be able to run the
    child process interactively for a while before kicking itself into
    the background so I can return to the parent process (while the
    child process is RUNNING in the background).  Can it be done?  And
    if it can, how?
    Please reply by E-mail.  Thanks in advance.
    Hon-Man Wong

Kantor & Lapsley [Page 26]

RFC 977 February 1986 Network News Transfer Protocol

5. References

 [1]  Crocker, D., "Standard for the Format of ARPA Internet Text
      Messages", RFC-822, Department of Electrical Engineering,
      University of Delaware, August, 1982.
 [2]  Horton, M., "Standard for Interchange of USENET Messages",
      RFC-850, USENET Project, June, 1983.
 [3]  Postel, J., "Transmission Control Protocol- DARPA Internet
      Program Protocol Specification", RFC-793, USC/Information
      Sciences Institute, September, 1981.
 [4]  Postel, J., "Simple Mail Transfer Protocol", RFC-821,
      USC/Information Sciences Institute, August, 1982.

6. Acknowledgements

 The authors wish to express their heartfelt thanks to those many
 people who contributed to this specification, and especially to Erik
 Fair and Chuq von Rospach, without whose inspiration this whole thing
 would not have been necessary.

7. Notes

 <1> UNIX is a trademark of Bell Laboratories.

Kantor & Lapsley [Page 27]

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