Movatterモバイル変換

Network Working Group                      Brian Kantor (U.C. San Diego)Request for Comments: 977                   Phil Lapsley (U.C. Berkeley)                                                           February 1986Network News Transfer Protocol                A Proposed Standard for the Stream-Based                          Transmission of NewsStatus 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.Kantor & Lapsley                                                [Page 1]

RFC 977                                                    February 1986Network News Transfer Protocol1.2.  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 onlyKantor & Lapsley                                                [Page 2]

RFC 977                                                    February 1986Network 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 inRFC 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).Kantor & Lapsley                                                [Page 3]

RFC 977                                                    February 1986Network 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.Kantor & Lapsley                                                [Page 4]

RFC 977                                                    February 1986Network News Transfer Protocol2.  The NNTP Specification2.1.  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.Kantor & Lapsley                                                [Page 5]

RFC 977                                                    February 1986Network News Transfer Protocol2.4.  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.Kantor & Lapsley                                                [Page 6]

RFC 977                                                    February 1986Network 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.)Kantor & Lapsley                                                [Page 7]

RFC 977                                                    February 1986Network News Transfer Protocol2.4.3.  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 performed3.  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.Kantor & Lapsley                                                [Page 8]

RFC 977                                                    February 1986Network 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 articleKantor & Lapsley                                                [Page 9]

RFC 977                                                    February 1986Network 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 byRFC850) 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 foundKantor & Lapsley                                               [Page 10]

RFC 977                                                    February 1986Network News Transfer Protocol3.2.  The GROUP command3.2.1.  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 groupKantor & Lapsley                                               [Page 11]

RFC 977                                                    February 1986Network News Transfer Protocol3.3.  The HELP command3.3.1.  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 follows3.4.  The IHAVE command3.4.1.  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 suchKantor & Lapsley                                               [Page 12]

RFC 977                                                    February 1986Network 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 command3.5.1.  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)Kantor & Lapsley                                               [Page 13]

RFC 977                                                    February 1986Network News Transfer Protocol   412 no newsgroup selected   420 no current article has been selected   422 no previous article in this group3.6.  The LIST command3.6.1.  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 followsKantor & Lapsley                                               [Page 14]

RFC 977                                                    February 1986Network News Transfer Protocol3.7.  The NEWGROUPS command3.7.1.  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 followsKantor & Lapsley                                               [Page 15]

RFC 977                                                    February 1986Network News Transfer Protocol3.8.  The NEWNEWS command3.8.1.  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 toKantor & Lapsley                                               [Page 16]

RFC 977                                                    February 1986Network 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 follows3.9.  The NEXT command3.9.1.  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 groupKantor & Lapsley                                               [Page 17]

RFC 977                                                    February 1986Network News Transfer Protocol3.10.  The POST command3.10.1.  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 byRFC850, 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.  SeeRFC850 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 failedKantor & Lapsley                                               [Page 18]

RFC 977                                                    February 1986Network 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 allowed3.11.  The QUIT command3.11.1.  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 command3.12.1.  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 notedKantor & Lapsley                                               [Page 19]

RFC 977                                                    February 1986Network News Transfer Protocol4.  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 1986Network 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 followKantor & Lapsley                                               [Page 21]

RFC 977                                                    February 1986Network 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 inRFC850 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 1986Network 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 1986Network 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   STAT4.7.2.  Responses   100 help text follows   199 debug outputKantor & Lapsley                                               [Page 24]

RFC 977                                                    February 1986Network 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 performed4.8.  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 NewsKantor & Lapsley                                               [Page 25]

RFC 977                                                    February 1986Network News Transfer Protocol   system is discussed in detail inRFC 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 consultRFC 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 WongKantor & Lapsley                                               [Page 26]

RFC 977                                                    February 1986Network News Transfer Protocol5.  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]