1 SESSION LAYER PROTOCOL FOR CITADEL/UX
2 (c) 1995-2002 by Art Cancro et. al. All Rights Reserved
8 This is an attempt to document the session layer protocol used by the
9 Citadel/UX system, beginning with version 4.00, which is the first version
10 to implement a client/server paradigm. It is intended as a resource for
11 programmers who intend to develop their own Citadel clients, but it may have
15 IMPORTANT NOTE TO DEVELOPERS!
16 -----------------------------
18 Anyone who wants to add commands or other functionality to this protocol,
19 *please* get in touch so that these efforts can be coordinated. New
20 commands added by other developers can be added to this document, so we
21 don't end up with new server commands from multiple developers which have
22 the same name but perform different functions. If you don't coordinate new
23 developments ahead of time, please at least send in an e-mail documenting
24 what you did, so that your new commands can be added to this document.
26 The coordinator of the Citadel/UX project is Art Cancro
27 <ajc@uncensored.citadel.org>.
30 CONNECTING TO A SERVER
31 ----------------------
33 The protocols used below the session layer are beyond the scope of this
34 document, but we will briefly cover the methodology employed by Citadel/UX.
36 Citadel/UX offers Citadel BBS service using TCP/IP. It does so via a
37 multithreaded server listening on a TCP port. Older (4.xx) versions employed
38 an inetd-based server.
40 The port number officially assigned to Citadel by the IANA is 504/tcp. Since
41 our session layer assumes a clean, reliable, sequenced connection, the use
42 of UDP would render the server unstable and unusable, so we stick with TCP.
45 GENERAL INFORMATION ABOUT THE SERVER
46 ------------------------------------
48 The server is connection-oriented and stateful: each client requires its own
49 connection to a server process, and when a command is sent, the client must
50 read the response, and then transfer data or change modes if necessary.
52 The session layer is very much like other Internet protocols such as SMTP
53 or NNTP. A client program sends one-line commands to the server, and the
54 server responds with a three-digit numeric result code followed by a message
55 describing what happened. This cycle continues until the end of the
58 Unlike protocols such as FTP, all data transfers occur in-band. This means
59 that the same connection that is used for exchange of client/server
60 messages, will also be used to transfer data back and forth. (FTP opens a
61 separate connection for data transfers.) This keeps protocol administration
62 straightforward, as it can traverse firewalls without any special protocol
63 support on the firewall except for opening the port number.
69 The server will respond to all commands with a 3-digit result code, which
70 will be the first three characters on the line. The rest of the line may
71 contain a human-readable string explaining what happened. (Some client
72 software will display some of these strings to the user.)
74 The first digit is the most important. The following codes are defined for
75 this position: ERROR, OK, MORE_DATA, LISTING_FOLLOWS, and SEND_LISTING.
77 The second and third digits may provide a reason as to why a command
78 succeeded or failed. See ipcdef.h for the available codes.
80 ERROR means the command did not complete.
81 OK means the command executed successfully.
82 MORE_DATA means the command executed partially. Usually this means that
83 another command needs to be executed to complete the operation. For example,
84 sending the USER command to log in a user usually results in a MORE_DATA
85 result code, because the client needs to execute a PASS command to send the
86 password and complete the login.
87 LISTING_FOLLOWS means that after the server response, the server will
88 output a listing of some sort. The client *must* read the listing, whether
89 it wants to or not. The end of the listing is signified by the string
90 "000" on a line by itself.
91 SEND_LISTING is the opposite of LISTING_FOLLOWS. It means that the client
92 should begin sending a listing of some sort. The client *must* send something,
93 even if it is an empty listing. Again, the listing ends with "000" on a line
95 BINARY_FOLLOWS and SEND_BINARY mean that the client must immediately send
96 or receive a block of binary data. The first parameter will always be the
98 ASYNC_MESSAGE_FOLLOWS means that an asynchronous, or unsolicited, message
99 follows. The next line will be one of the above codes, and if a data transfer
100 is involved it must be handled immediately. Note that the client will not
101 receive this type of response unless it indicates to the server that it is
102 capable of handling them; see the writeup of the ASYN command later in this
108 Zero or more parameters may be passed to a command. When more than one
109 parameter is passed to a command, they should be separated by the "|"
112 In this example, we're using the "SETU" command and passing three
113 parameters: 80, 24, and 260.
115 When the server spits out data that has parameters, if more than one
116 parameter is returned, they will be separated by the "|" symbol like
119 In this example, we just executed the "GETU" command, and it returned us
120 an OK result code (the '2' in the 200) and three parameters: 80, 24, and
127 This is a listing of all the commands that a Citadel/UX server can execute.
132 This command does nothing. It takes no arguments and always returns
133 OK. It is intended primarily for testing and development, but it might also
134 be used as a "keep alive" command to prevent the server from timing out, if
135 it's running over a transport that needs this type of thing.
138 ECHO (ECHO something)
140 This command also does nothing. It simply returns OK followed by whatever
146 Terminate the server connection. This command takes no arguments. It
147 returns OK and closes the connection immediately.
152 Log out the user without closing the server connection. It always returns
153 OK even if no user is logged in.
156 USER (send USER name)
158 The first step in logging in a user. This command takes one argument: the
159 name of the user to be logged in. If the user exists, a MORE_DATA return
160 code will be sent, which means the client should execute PASS as the next
161 command. If the user does not exist, ERROR is returned.
166 The second step in logging in a user. This command takes one argument: the
167 password for the user we are attempting to log in. If the password doesn't
168 match the correct password for the user we specified for the USER command,
169 or if a USER command has not been executed yet, ERROR is returned. If the
170 password is correct, OK is returned and the user is now logged in... and
171 most of the other server commands can now be executed. Along with OK, the
172 following parameters are returned:
174 0 - The user's name (in case the client wants the right upper/lower casing)
175 1 - The user's current access level
178 4 - Various flags (see citadel.h)
180 6 - Time of last call (UNIX timestamp)
183 NEWU (create NEW User account)
185 This command creates a new user account AND LOGS IT IN. The argument to
186 this command will be the name of the account. No case conversion is done
187 on the name. Note that the new account is installed with a default
188 configuration, and no password, so the client should immediately prompt the
189 user for a password and install it with the SETP command as soon as this
190 command completes. This command returns OK if the account was created and
191 logged in, or ERROR if another user already exists with this name. If OK,
192 it will also return the same parameters that PASS returns.
194 Please note that the NEWU command should only be used for self-service user account
195 creation. For administratively creating user accounts, please use the CREU command.
198 SETP (SET new Password)
200 This command sets a new password for the currently logged in user. The
201 argument to this command will be the new password. The command always
202 returns OK, unless the client is not logged in, in which case it will return
206 CREU (CREate new User account)
208 This command creates a new user account AND DOES NOT LOG IT IN. The argument to
209 this command will be the name of the account. No case conversion is done
210 on the name. Note that the new account is installed with a default
211 configuration, and no password. This command returns OK if the account was created,
212 or ERROR if another user already exists with this name.
214 Please note that CREU is intended to be used for activities in which a system
215 administrator is creating user accounts. For self-service user account creation,
216 use the NEWU command.
220 LKRN (List Known Rooms with New messages)
222 List known rooms with new messages. If the client is not logged in, ERROR
223 is returned. Otherwise, LISTING_FOLLOWS is returned, followed by the room
224 listing. Each line in the listing contains the full name of a room, followed
225 by the '|' symbol, and then a number that may contain the following bits:
228 #define QR_PERMANENT 1 /* Room does not purge */
229 #define QR_PRIVATE 4 /* Set for any type of private room */
230 #define QR_PASSWORDED 8 /* Set if there's a password too */
231 #define QR_GUESSNAME 16 /* Set if it's a guessname room */
232 #define QR_DIRECTORY 32 /* Directory room */
233 #define QR_UPLOAD 64 /* Allowed to upload */
234 #define QR_DOWNLOAD 128 /* Allowed to download */
235 #define QR_VISDIR 256 /* Visible directory */
236 #define QR_ANONONLY 512 /* Anonymous-Only room */
237 #define QR_ANON2 1024 /* Anonymous-Option room */
238 #define QR_NETWORK 2048 /* Shared network room */
239 #define QR_PREFONLY 4096 /* Preferred status needed to enter */
240 #define QR_READONLY 8192 /* Aide status required to post */
243 Other bits may be defined in the future. The listing terminates, as with
244 all listings, with "000" on a line by itself.
246 Starting with version 4.01 and above, floors are supported. The first
247 argument to LKRN should be the number of the floor to list rooms from. Only
248 rooms from this floor will be listed. If no arguments are passed to LKRN, or
249 if the floor number requested is (-1), rooms on all floors will be listed.
251 The third field displayed on each line is the number of the floor the room
252 is on. The LFLR command should be used to associate floor numbers with
255 The fourth field displayed on each line is a "room listing order." Unless
256 there is a compelling reason not to, clients should sort any received room
257 listings by this value.
261 LKRO (List Known Rooms with Old [no new] messages)
263 This follows the same usage and format as LKRN.
266 LZRM (List Zapped RooMs)
268 This follows the same usage and format as LKRN and LKRO.
271 LKRA (List All Known Rooms)
273 Same format. Lists all known rooms, with or without new messages.
276 LRMS (List all accessible RooMS)
278 Again, same format. This command lists all accessible rooms, known and
279 forgotten, with and without new messages. It does not, however, list
280 inaccessible private rooms.
283 GETU (GET User configuration)
285 This command retrieves the screen dimensions and user options for the
286 currently logged in account. ERROR will be returned if no user is logged
287 in, of course. Otherwise, OK will be returned, followed by four parameters.
288 The first parameter is the user's screen width, the second parameter is the
289 user's screen height, and the third parameter is a bag of bits with the
292 #define US_LASTOLD 16 /* Print last old message with new */
293 #define US_EXPERT 32 /* Experienced user */
294 #define US_UNLISTED 64 /* Unlisted userlog entry */
295 #define US_NOPROMPT 128 /* Don't prompt after each message */
296 #define US_DISAPPEAR 512 /* Use "disappearing msg prompts" */
297 #define US_PAGINATOR 2048 /* Pause after each screen of text */
299 There are other bits, too, but they can't be changed by the user (see below).
302 SETU (SET User configuration)
304 This command does the opposite of SETU: it takes the screen dimensions and
305 user options (which were probably obtained with a GETU command, and perhaps
306 modified by the user) and writes them to the user account. This command
307 should be passed three parameters: the screen width, the screen height, and
308 the option bits (see above).
310 Note that there exist bits here which are not listed in this document. Some
311 are flags that can only be set by Aides or the system administrator. SETU
312 will ignore attempts to toggle these bits. There also may be more user
313 settable bits added at a later date. To maintain later downward compatibility,
314 the following procedure is suggested:
316 1. Execute GETU to read the current flags
317 2. Toggle the bits that we know we can toggle
318 3. Execute SETU to write the flags
320 If we are passed a bit whose meaning we don't know, it's best to leave it
321 alone, and pass it right back to the server. That way we can use an old
322 client on a server that uses an unknown bit without accidentally clearing
323 it every time we set the user's configuration.
328 This command is used to goto a new room. When the user first logs in (login
329 is completed after execution of the PASS command) this command is
330 automatically and silently executed to take the user to the first room in the
331 system (usually called the Lobby).
333 This command can be passed one or two parameters. The first parameter is,
334 of course, the name of the room. Although it is not case sensitive, the
335 full name of the room must be used. Wildcard matching or unique string
336 matching of room names should be the responsibility of the client.
338 Note that the reserved room name "_BASEROOM_" can be passed to the server
339 to cause the goto command to take the user to the first room in the system,
340 traditionally known as the Lobby>. As long as a user is logged in, a
341 GOTO command to _BASEROOM_ is guaranteed to succeed. This is useful to
342 allow client software to return to the base room when it doesn't know
345 There are also two additional reserved room names:
346 "_MAIL_" translates to the system's designated room for e-mail messages.
347 "_BITBUCKET_" goes to whatever room has been chosen for messages
350 The second (and optional) parameter is a password, if one is required for
351 access to the room. This allows for all types of rooms to be accessed via
352 this command: for public rooms, invitation-only rooms to which the user
353 has access, and preferred users only rooms to which the user has access, the
354 room will appear in a room listing. For guess-name rooms, this command
355 will work transparently, adding the room to the user's known room list when
356 it completes. For passworded rooms, access will be denied if the password
357 is not supplied or is incorrect, or the command will complete successfully
358 if the password is correct.
360 The third (and also) optional parameter is a "transient" flag. Normally,
361 when a user enters a private and/or zapped room, the room is added to the
362 user's known rooms list. If the transient flag is set to non-zero, this is
363 called a "transient goto" which causes the user to enter the room without
364 adding the room to the known rooms list.
366 The possible result codes are:
368 OK - The command completed successfully. User is now in the room.
369 (See the list of returned parameters below)
371 ERROR - The command did not complete successfully. Check the second and
372 third positions of the result code to find out what happened:
374 NOT_LOGGED_IN - Of course you can't go there. You didn't log in.
375 PASSWORD_REQUIRED - Either a password was not supplied, or the supplied
376 password was incorrect.
377 NO_SUCH_ROOM - The requested room does not exist.
379 The typical procedure for entering a passworded room would be:
381 1. Execute a GOTO command without supplying any password.
382 2. ERROR+PASSWORD_REQUIRED will be returned. The client now knows that
383 the room is passworded, and prompts the user for a password.
384 3. Execute a GOTO command, supplying both the room name and the password.
385 4. If OK is returned, the command is complete. If, however,
386 ERROR+PASSWORD_REQUIRED is still returned, tell the user that the supplied
387 password was incorrect. The user remains in the room he/she was previously
390 When the command succeeds, these parameters are returned:
391 0. The name of the room
392 1. Number of unread messages in this room
393 2. Total number of messages in this room
394 3. Info flag: set to nonzero if the user needs to read this room's info
395 file (see RINF command below)
396 4. Various flags associated with this room. (See LKRN cmd above)
397 5. The highest message number present in this room
398 6. The highest message number the user has read in this room
399 7. Boolean flag: 1 if this is a Mail> room, 0 otherwise.
400 8. Aide flag: 1 if the user is either the Room Aide for this room, *or* is
401 a regular Aide (this makes access checks easy).
402 9. The number of new Mail messages the user has (useful for alerting the
403 user to the arrival of new mail during a session)
404 10. The floor number this room resides on
405 11. The current "view" for this room (see views.txt for more info)
408 MSGS (get pointers to MeSsaGeS in this room)
410 This command obtains a listing of all the messages in the current room
411 which the client may request. This command may be passed a single parameter:
412 either "all", "old", or "new" to request all messages, only old messages, or
413 new messages. Or it may be passed two parameters: "last" plus a number, in
414 which case that many message pointers will be returned, or "first" plus a
415 number, for the corresponding effect. If no parameters are specified, "all"
418 In Citadel/UX 5.00 and above, the client may also specify "gt" plus a number,
419 to list all messages in the current room with a message number greater than
422 The third argument, valid only in Citadel/UX 5.60 and above, may be either
423 0 or 1. If it is 1, this command behaves differently: before a listing is
424 returned, the client must transmit a list of fields to search for. The field
425 headers are listed below in the writeup for the "MSG0" command.
427 This command can return three possible results. An ERROR code may be returned
428 if no user is currently logged in or if something else went wrong. Otherwise,
429 LISTING_FOLLOWS will be returned, and the listing will consist of zero or
430 more message numbers, one per line. The listing ends, as always, with the
431 string "000" alone on a line by itself. The listed message numbers can be used
432 to request messages from the system. If "search mode" is being used, the
433 server will return START_CHAT_MODE, and the client is expected to transmit
434 the search criteria, and then read the message list.
436 Since this is somewhat complex, here are some examples:
438 Example 1: Read all new messages
441 Server: 100 Message list...
447 Example 2: Read the last five messages
450 Server: 100 Message list...
458 Example 3: Read all messages written by "IGnatius T Foobar"
461 Server: 800 Send template then receive message list
462 Client: from|IGnatius T Foobar
476 Note that in "search mode" the client may specify any number of search
477 criteria. These criteria are applied with an AND logic.
481 MSG0 (read MeSsaGe, mode 0)
483 This is a command used to read the text of a message. "Mode 0" implies that
484 other MSG commands (MSG1, MSG2, etc.) will probably be added later on to read
485 messages in more robust formats. This command should be passed two arguments.
486 The first is the message number of the message being requested. In server
487 version 4.04 and above, the second argument may be set to either 0 to read the
488 entire message, or 1 to read the headers only.
490 The server should, of course, make sure that the client actually has access
491 to the message being requested before honoring this request. Citadel/UX does
492 so by checking the message number against the contents of the current room. If
493 it's not there, the request is denied.
495 If the request is denied, an ERROR code will be returned. Otherwise, the
496 LISTING_FOLLOWS code will be returned, followed by the contents of the message.
497 The following fields may be sent:
499 type= Formatting type. The currently defined types are:
500 0 = "traditional" Citadel formatting. This means that newlines should be
501 treated as spaces UNLESS the first character on the next line is a space. In
502 other words, only indented lines should generate a newline on the user's screen
503 when the message is being displayed. This allows a message to be formatted to
504 the reader's screen width. It also allows the use of proportional fonts.
505 1 = a simple fixed-format message. The message should be displayed to
506 the user's screen as is, preferably in a fixed-width font that will fit 80
508 4 = MIME format message. The message text is expected to contain a header
509 with the "Content-type:" directive (and possibly others).
511 msgn= The message ID of this message on the system it originated on.
512 path= An e-mailable path back to the user who wrote the message.
514 time= The date and time of the message, in Unix format (the number of
515 seconds since midnight on January 1, 1970, GMT).
517 from= The name of the author of the message.
518 rcpt= If the message is a private e-mail, this is the recipient.
519 room= The name of the room the message originated in.
520 node= The short node name of the system this message originated on.
521 hnod= The long node name of the system this message originated on.
522 zaps= The id/node of a message which this one zaps (supersedes).
524 text Note that there is no "=" after the word "text". This string
525 signifies that the message text begins on the next line.
528 WHOK (WHO Knows room)
530 This command is available only to Aides. ERROR+HIGHER_ACCESS_REQUIRED will
531 be returned if the user is not an Aide. Otherwise, it returns
532 LISTING_FOLLOWS and then lists, one user per line, every user who has
533 access to the current room.
536 INFO (get server INFO)
538 This command will *always* return LISTING_FOLLOWS and then print out a
539 listing of zero or more strings. Client software should be written to expect
540 anywhere from a null listing to an infinite number of lines, to allow later
541 backward compatibility. The current implementation defines the following
542 parts of the listing:
544 Line 1 - Your unique session ID on the server
545 Line 2 - The node name of the server BBS
546 Line 3 - Human-readable node name of the server BBS
547 Line 4 - The fully-qualified domain name (FQDN) of the server
548 Line 5 - The name of the server software, i.e. "Citadel/UX 4.00"
549 Line 6 - (The revision level of the server code) * 100
550 Line 7 - The geographical location of the BBS (city and state if in the US)
551 Line 8 - The name of the system administrator
552 Line 9 - A number identifying the server type (see below)
553 Line 10 - The text of the system's paginator prompt
554 Line 11 - Floor Flag. 1 if the system supports floors, 0 otherwise.
555 Line 12 - Paging level. 0 if the system only supports inline paging,
556 1 if the system supports "extended" paging (check-only and
557 multiline modes). See the SEXP command for further information.
558 Line 13 - The "nonce" for this session, for support of APOP-style
559 authentication. If this field is present, clients may authenticate
561 Line 14 - Set to nonzero if this server supports the QNOP command.
563 *** NOTE! *** The "server type" code is intended to promote global
564 compatibility in a scenario in which developers have added proprietary
565 features to their servers or clients. We are attempting to avoid a future
566 situation in which users need to keep different client software around for
567 each BBS they use. *Please*, if you are a developer and plan to add
568 proprietary features:
570 -> Your client programs should still be able to utilize servers other than
572 -> Clients other than your own should still be able to utilize your server,
573 even if your proprietary extensions aren't supported.
574 -> Please contact Art Cancro <ajc@uncensored.citadel.org> and obtain a unique
575 server type code, which can be assigned to your server program.
576 -> If you document what you did in detail, perhaps it can be added to a
577 future release of the Citadel/UX program, so everyone can enjoy it. Better
578 yet, just work with the Citadel development team on the main source tree.
580 If everyone follows this scheme, we can avoid a chaotic situation with lots
581 of confusion about which client program works with which server, etc. Client
582 software can simply check the server type (and perhaps the revision level)
583 to determine ahead of time what commands may be utilized.
585 Please refer to "developers.txt" for information on what codes belong to whom.
589 RDIR (Read room DIRectory)
591 Use this command to read the directory of a directory room. ERROR+NOT_HERE
592 will be returned if the room has no directory, or some other error; ERROR +
593 HIGHER_ACCESS_REQUIRED will be returned if the room's directory is not
594 visible and the user does not have Aide or Room Aide privileges; otherwise
595 LISTING_FOLLOWS will be returned, followed by the room's directory. Each
596 line of the directory listing will contain three fields: a filename, the
597 length of the file, and a description.
599 The server message contained on the same line with LISTING_FOLLOWS will
600 contain the name of the system and the name of the directory, such as:
601 uncensored.citadel.org|/usr/bbs/files/my_room_directory
604 SLRP (Set Last-message-Read Pointer)
606 This command marks all messages in the current room as read (seen) up to and
607 including the specified number. Its sole parameter
608 is the number of the last message that has been read. This allows the pointer
609 to be set at any arbitrary point in the room. Optionally, the parameter
610 "highest" may be used instead of a message number, to set the pointer to the
611 number of the highest message in the room, effectively marking all messages
612 in the room as having been read (ala the Citadel <G>oto command).
614 The command will return OK if the pointer was set, or ERROR if something
615 went wrong. If OK is returned, it will be followed by a single argument
616 containing the message number the last-read-pointer was set to.
619 INVT (INViTe a user to a room)
621 This command may only be executed by Aides, or by the room aide for the
622 current room. It is used primarily to add users to invitation-only rooms,
623 but it may also be used in other types of private rooms as well. Its sole
624 parameter is the name of the user to invite.
626 The command will return OK if the operation succeeded, or ERROR if it did
627 not. ERROR+HIGHER_ACCESS_REQUIRED may also be returned if the operation
628 would have been possible if the user had higher access, and ERROR+NOT_HERE
629 may be returned if the room is not a private room.
632 KICK (KICK a user out of a room)
634 This is the opposite of INVT: it is used to kick a user out of a private
635 room. It can also be used to kick a user out of a public room, but the
636 effect will only be the same as if the user <Z>apped the room - a non-stupid
637 user can simply un-zap the room to get back in.
640 GETR (GET Room attributes)
642 This command is used for editing the various attributes associated with a
643 room. A typical "edit room" command would work like this:
644 1. Use the GETR command to get the current attributes
645 2. Change some of them around
646 3. Use SETR (see below) to save the changes
647 4. Possibly also change the room aide using the GETA and SETA commands
649 GETR takes no arguments. It will only return OK if the SETR command will
650 also return OK. This allows client software to tell the user that he/she
651 can't edit the room *before* going through the trouble of actually doing the
652 editing. Possible return codes are:
654 ERROR+NOT_LOGGED_IN - No user is logged in.
655 ERROR+HIGHER_ACCESS_REQUIRED - Not enough access. Typically, only aides
656 and the room aide associated with the current room, can access this command.
657 ERROR+NOT_HERE - Lobby>, Mail>, and Aide> cannot be edited.
658 OK - Command succeeded. Parameters are returned.
660 If OK is returned, the following parameters will be returned as well:
662 0. The name of the room
663 1. The room's password (if it's a passworded room)
664 2. The name of the room's directory (if it's a directory room)
665 3. Various flags (bits) associated with the room (see LKRN cmd above)
666 4. The floor number on which the room resides
667 5. The room listing order
668 6. The default view for the room (see views.txt)
671 SETR (SET Room attributes)
673 This command sets various attributes associated with the current room. It
674 should be passed the following arguments:
676 0. The name of the room
677 1. The room's password (if it's a passworded room)
678 2. The name of the room's directory (if it's a directory room)
679 3. Various flags (bits) associated with the room (see LKRN cmd above)
680 4. "Bump" flag (see below)
681 5. The floor number on which the room should reside
682 6. The room listing order
683 7. The default view for the room (see views.txt)
685 *Important: You should always use GETR to retrieve the current attributes of
686 the room, then change what you want to change, and then use SETR to write it
687 all back. This is particularly important with respect to the flags: if a
688 particular bit is set, and you don't know what it means, LEAVE IT ALONE and
689 only toggle the bits you want to toggle. This will allow for upward
692 If the room is a private room, you have the option of causing all users who
693 currently have access, to forget the room. If you want to do this, set the
694 "bump" flag to 1, otherwise set it to 0.
699 This command is used to get the name of the Room Aide for the current room.
700 It will return ERROR+NOT_LOGGED_IN if no user is logged in, ERROR if there
701 is no current room, or OK if the command succeeded. Along with OK there will
702 be returned one parameter: the name of the Room Aide.
707 The opposite of GETA, used to set the Room Aide for the current room. One
708 parameter should be passed, which is the name of the user who is to be the
709 new Room Aide. Under Citadel/UX, this command may only be executed by Aides
710 and by the *current* Room Aide for the room. Return codes possible are:
711 ERROR+NOT_LOGGED_IN (Not logged in.)
712 ERROR+HIGHER_ACCESS_REQUIRED (Higher access required.)
713 ERROR+NOT_HERE (No current room, or room cannot be edited.
714 Under Citadel/UX, the Lobby> Mail> and Aide> rooms are non-editable.)
715 OK (Command succeeded.)
718 ENT0 (ENTer message, mode 0)
720 This command is used to enter messages into the system. It accepts four
723 0 - Post flag. This should be set to 1 to post a message. If it is
724 set to 0, the server only returns OK or ERROR (plus any flags describing
725 the error) without reading in a message. Client software should, in fact,
726 perform this operation at the beginning of an "enter message" command
727 *before* starting up its editor, so the user does not end up typing a message
728 in vain that will not be permitted to be saved. If it is set to 2, the
729 server will accept an "apparent" post name if the user is privileged enough.
730 This post name is arg 4.
731 1 - Recipient. This argument is utilized only for private mail messages.
732 It is ignored for public messages. It contains, of course, the name of the
733 recipient of the message.
734 2 - Anonymous flag. This argument is ignored unless the room allows
735 anonymous messages. In such rooms, this flag may be set to 1 to flag a
736 message as anonymous, otherwise 0 for a normal message.
737 3 - Format type. Any valid Citadel/UX format type may be used (this will
738 typically be 0; see the MSG0 command above).
739 4 - Post name. When postflag is 2, this is the name you are posting as.
740 This is an Aide only command.
742 Possible result codes:
743 OK - The request is valid. (Client did not set the "post" flag, so the
744 server will not read in message text.) If the message is an e-mail with
745 a recipient, the text that follows the OK code will contain the exact name
746 to which mail is being sent. The client can display this to the user. The
747 implication here is that the name that the server returns will contain the
748 correct upper and lower case characters. In addition, if the recipient is
749 having his/her mail forwarded, the forwarding address will be returned.
750 SEND_LISTING - The request is valid. The client should now transmit
751 the text of the message (ending with a 000 on a line by itself, as usual).
752 ERROR - Miscellaneous error. (Explanation probably follows.)
753 ERROR + NOT_LOGGED_IN - Not logged in.
754 ERROR + HIGHER_ACCESS_REQUIRED - Higher access is required. An
755 explanation follows, worded in a form that can be displayed to the user.
756 ERROR + NO_SUCH_USER - The specified recipient does not exist.
759 RINF (read Room INFormation file)
761 Each room has associated with it a text file containing a description of
762 the room, perhaps containing its intended purpose or other important
763 information. The info file for the Lobby> (the system's base room) is
764 often used as a repository for system bulletins and the like.
766 This command, which accepts no arguments, is simply used to read the info
767 file for the current room. It will return LISTING_FOLLOWS followed by
768 the text of the message (always in format type 0) if the request can be
769 honored, or ERROR if no info file exists for the current room (which is
770 often the case). Other error description codes may accompany this result.
772 When should this command be used? This is, of course, up to the discretion
773 of client software authors, but in Citadel it is executed in two situations:
774 the first time the user ever enters a room; and whenever the contents of the
775 file change. The latter can be determined from the result of a GOTO command,
776 which will tell the client whether the file needs to be read (see GOTO above).
779 DELE (DELEte a message)
781 Delete a message from the current room. The one argument that should be
782 passed to this command is the message number of the message to be deleted.
783 The return value will be OK if the message was deleted, or an ERROR code.
784 If the delete is successful, the message's reference count is decremented, and
785 if the reference count reaches zero, the message is removed from the message
789 MOVE (MOVE or copy a message to a different room)
791 Move a message to a different room. The two arguments that should be passed
792 to this command are the message number of the message to be deleted, and the
793 name of the target room. If the operation succeeds, the message will be
794 deleted from the current room and moved to the target room. An ERROR code
795 usually means that either the user does not have permission to perform this
796 operation, or that the target room does not exist.
798 In Citadel/UX 5.55 and above, a third argument may be specified: 0 or 1 to
799 designate whether the message should be moved (0) or copied (1) to the target
800 room. In the case of a "copy" operation, the message's reference count is
801 incremented, and a pointer to the message will exist in both the source *and*
802 target rooms. In the case of a "move" operation, the message pointer is
803 deleted from the source room and the reference count remains the same.
806 KILL (KILL current room)
808 This command deletes the current room. It accepts a single argument, which
809 should be nonzero to actually delete the room, or zero to merely check
810 whether the room can be deleted.
812 Once the room is deleted, the current room is undefined. It is suggested
813 that client software immediately GOTO another room (usually _BASEROOM_)
814 after this command completes.
816 Possible return codes:
818 OK - room has been deleted (or, if checking only, request is valid).
819 ERROR+NOT_LOGGED_IN - no user is logged in.
820 ERROR+HIGHER_ACCESS_REQUIRED - not enough access to delete rooms.
821 ERROR+NOT_HERE - this room can not be deleted.
824 CRE8 (CRE[ate] a new room)
826 This command is used to create a new room. Like some of the other
827 commands, it provides a mechanism to first check to see if a room can be
828 created before actually executing the command. CRE8 accepts the following
831 0 - Create flag. Set this to 1 to actually create the room. If it is
832 set to 0, the server merely checks that there is a free slot in which to
833 create a new room, and that the user has enough access to create a room. It
834 returns OK if the client should go ahead and prompt the user for more info,
835 or ERROR or ERROR+HIGHER_ACCESS_REQUIRED if the command will not succeed.
836 1 - Name for new room.
837 2 - Access type for new room:
839 1 - Private; can be entered by guessing the room's name
840 2 - Private; can be entered by knowing the name *and* password
841 3 - Private; invitation only (sometimes called "exclusive")
842 3 - Password for new room (if it is a type 2 room)
843 4 - Floor number on which the room should reside (optional)
844 5 - Set to 1 to avoid automatically gaining access to the created room.
846 If the create flag is set to 1, the room is created (unless something
847 went wrong and an ERROR return is sent), and the server returns OK, but
848 the session is **not** automatically sent to that room. The client still
849 must perform a GOTO command to go to the new room.
852 FORG (FORGet the current room)
854 This command is used to forget (zap) the current room. For those not
855 familiar with Citadel, this terminology refers to removing the room from
856 a user's own known rooms list, *not* removing the room itself. After a
857 room is forgotten, it no longer shows up in the user's known room list,
858 but it will exist in the user's forgotten room list, and will return to the
859 known room list if the user goes to the room (in Citadel, this is
860 accomplished by explicitly typing the room's name in a <.G>oto command).
862 The command takes no arguments. If the command cannot execute for any
863 reason, ERROR will be returned. ERROR+NOT_LOGGED_IN or ERROR+NOT_HERE may
864 be returned as they apply.
866 If the command succeeds, OK will be returned. At this point, the current
867 room is **undefined**, and the client software is responsible for taking
868 the user to another room before executing any other room commands (usually
869 this will be _BASEROOM_ since it is always there).
872 MESG (read system MESsaGe)
874 This command is used to display system messages and/or help files. The
875 single argument it accepts is the name of the file to display. IT IS CASE
876 SENSITIVE. Citadel/UX looks for these files first in the "messages"
877 subdirectory and then in the "help" subdirectory.
879 If the file is found, LISTING_FOLLOWS is returned, followed by a pathname
880 to the file being displayed. Then the message is printed, in format type 0
881 (see MSG0 command for more information on this). If the file is not found,
884 There are some "well known" names of system messages which client software
885 may expect most servers to carry:
887 hello - Welcome message, to be displayed before the user logs in.
888 changepw - To be displayed whenever the user is prompted for a new
889 password. Warns about picking guessable passwords and such.
890 register - Should be displayed prior to the user entering registration.
891 Warnings about not getting access if not registered, etc.
892 help - Main system help file.
893 goodbye - System logoff banner; display when user logs off.
894 roomaccess - Information about how public rooms and different types of
895 private rooms function with regards to access.
896 unlisted - Tells users not to choose to be unlisted unless they're
897 really paranoid, and warns that aides can still see
898 unlisted userlog entries.
900 Citadel/UX provides these for the Citadel/UX Unix text client. They are
901 probably not very useful for other clients:
903 mainmenu - Main menu (when in idiot mode).
908 saveopt - Options to save a message, abort, etc.
909 entermsg - Displayed just before a message is entered, when in
913 GNUR (Get Next Unvalidated User)
915 This command shows the name of a user that needs to be validated. If there
916 are no unvalidated users, OK is returned. Otherwise, MORE_DATA is returned
917 along with the name of the first unvalidated user the server finds. All of
918 the usual ERROR codes may be returned as well (for example, if the user is
919 not an Aide and cannot validate users).
921 A typical "Validate New Users" command would keep executing this command,
922 and then validating each user it returns, until it returns OK when all new
923 users have been validated.
926 GREG (Get REGistration for user)
928 This command retrieves the registration info for a user, whose name is the
929 command's sole argument. All the usual error messages can be returned. If
930 the command succeeds, LISTING_FOLLOWS is returned, followed by the user's name
931 (retrieved from the userlog, with the right upper and lower case etc.) The
932 contents of the listing contains one field per line, followed by the usual
933 000 on the last line.
935 The following lines are defined. Others WILL be added in the futre, so all
936 software should be written to read the lines it knows about and then ignore
942 Line 4: Street address or PO Box
943 Line 5: City/town/village/etc.
944 Line 6: State/province/etc.
946 Line 8: Telephone number
948 Line 10: Internet e-mail address
951 Users without Aide privileges may retrieve their own registration using
952 this command. This can be accomplished either by passing the user's own
953 name as the argument, or the string "_SELF_". The command will always
954 succeed when used in this manner, unless no user is logged in.
959 This command is used to validate users. Obviously, it can only be executed
960 by users with Aide level access. It should be passed two parameters: the
961 name of the user to validate, and the desired access level
963 If the command succeeds, OK is returned. The user's access level is changed
964 and the "need validation" bit is cleared. If the command fails for any
965 reason, ERROR, ERROR+NO_SUCH_USER, or ERROR+HIGHER_ACCESS_REQUIRED will be
969 EINF (Enter INFo file for room)
971 Transmit the info file for the current room with this command. EINF uses
972 a boolean flag (1 or 0 as the first and only argument to the command) to
973 determine whether the client actually wishes to transmit a new info file, or
974 is merely checking to see if it has permission to do so.
976 If the command cannot succeed, it returns ERROR.
977 If the client is only checking for permission, and permission will be
978 granted, OK is returned.
979 If the client wishes to transmit the new info file, SEND_LISTING is
980 returned, and the client should transmit the text of the info file, ended
981 by the usual 000 on a line by itself.
986 This is a simple user listing. It always succeeds, returning
987 LISTING_FOLLOWS followed by zero or more user records, 000 terminated. The
988 fields on each line are as follows:
993 4. Date/time of last login (Unix format)
996 7. Password (listed only if the user requesting the list is an Aide)
998 Unlisted entries will also be listed to Aides logged into the server, but
999 not to ordinary users.
1002 REGI (send REGIstration)
1004 Clients will use this command to transmit a user's registration info. If
1005 no user is logged in, ERROR+NOT_LOGGED_IN is returned. Otherwise,
1006 SEND_LISTING is returned, and the server will expect the following information
1007 (terminated by 000 on a line by itself):
1010 Line 2: Street address or PO Box
1011 Line 3: City/town/village/etc.
1012 Line 4: State/province/etc.
1014 Line 6: Telephone number
1015 Line 7: e-mail address
1019 CHEK (CHEcK various things)
1021 When logging in, there are various things that need to be checked. This
1022 command will return ERROR+NOT_LOGGED_IN if no user is logged in. Otherwise
1023 it returns OK and the following parameters:
1025 0: Number of new private messages in Mail>
1026 1: Nonzero if the user needs to register
1027 2: (Relevant to Aides only) Nonzero if new users require validation
1030 DELF (DELete a File)
1032 This command deletes a file from the room's directory, if there is one. The
1033 name of the file to delete is the only parameter to be supplied. Wildcards
1034 are not acceptable, and any slashes in the filename will be converted to
1035 underscores, to prevent unauthorized access to neighboring directories. The
1036 possible return codes are:
1038 OK - Command succeeded. The file was deleted.
1039 ERROR+NOT_LOGGED_IN - Not logged in.
1040 ERROR+HIGHER_ACCESS_REQUIRED - Not an Aide or Room Aide.
1041 ERROR+NOT_HERE - There is no directory in this room.
1042 ERROR+FILE_NOT_FOUND - Requested file was not found.
1047 This command is similar to DELF, except that it moves a file (and its
1048 associated file description) to another room. It should be passed two
1049 parameters: the name of the file to move, and the name of the room to move
1050 the file to. All of the same return codes as DELF may be returned, and also
1051 one additional one: ERROR+NO_SUCH_ROOM, which means that the target room
1052 does not exist. ERROR+NOT_HERE could also mean that the target room does
1053 not have a directory.
1056 NETF (NETwork send a File)
1058 This command is similar to MOVF, except that it attempts to send a file over
1059 the network to another system. It should be passed two parameters: the name
1060 of the file to send, and the node name of the system to send it to. All of
1061 the same return codes as MOVF may be returned, except for ERROR+NO_SUCH_ROOM.
1062 Instead, ERROR+NO_SUCH_SYSTEM may be returned if the name of the target
1065 The name of the originating room will be sent along with the file. Most
1066 implementations will look for a room with the same name at the receiving end
1067 and attempt to place the file there, otherwise it goes into a bit bucket room
1068 for miscellaneous files. This is, however, beyond the scope of this document;
1069 see elsewhere for more details.
1072 RWHO (Read WHO's online)
1074 Displays a list of all users connected to the server. No error codes are
1075 ever returned. LISTING_FOLLOWS will be returned, followed by zero or more
1076 lines containing the following three fields:
1078 0 - Session ID. Citadel/UX fills this with the pid of a server program.
1080 2 - The name of the room the user is currently in. This field might not
1081 be displayed (for example, if the user is in a private room) or it might
1082 contain other information (such as the name of a file the user is
1084 3 - (server v4.03 and above) The name of the host the client is connecting
1085 from, or "localhost" if the client is local.
1086 4 - (server v4.04 and above) Description of the client software being used
1087 5 - The last time, locally to the server, that a command was received from
1088 this client (Note: NOOP's don't count)
1089 6 - The last command received from a client. (NOOP's don't count)
1090 7 - Session flags. These are: + (spoofed address), - (STEALTH mode), *
1091 (posting) and . (idle).
1092 8 - Actual user name, if user name is masqueraded and viewer is an Aide.
1093 9 - Actual room name, if room name is masqueraded and viewer is an Aide.
1094 10 - Actual host name, if host name is masqueraded and viewer is an Aide.
1096 The listing is terminated, as always, with the string "000" on a line by
1100 OPEN (OPEN a file for download)
1102 This command is used to open a file for downloading. Only one download
1103 file may be open at a time. The only argument to this command is the name
1104 of the file to be opened. The user should already be in the room where the
1105 file resides. Possible return codes are:
1108 ERROR+NOT_HERE (no directory in this room)
1109 ERROR+FILE_NOT_FOUND (could not open the file)
1113 If the file is successfully opened, OK will be returned, along with the
1114 size (in bytes) of the file, the time of last modification (if applicable),
1115 the filename (if known), and the MIME type of the file (if known).
1118 CLOS (CLOSe the download file)
1120 This command is used to close the download file. It returns OK if the
1121 file was successfully closed, or ERROR if there wasn't any file open in the
1125 READ (READ from the download file)
1127 Two arguments are passed to this command. The first is the starting position
1128 in the download file, and the second is the total number of bytes to be
1129 read. If the operation can be performed, BINARY_FOLLOWS will be returned,
1130 along with the number of bytes to follow. Then, immediately following the
1131 newline, will be that many bytes of binary data. The client *must* read
1132 exactly that number of bytes, otherwise the client and server will get out
1135 If the operation cannot be performed, any of the usual error codes will be
1139 UOPN (OPeN a file for Uploading)
1141 This command is similar to OPEN, except that this one is used when the
1142 client wishes to upload a file to the server. The first argument is the name
1143 of the file to create, and the second argument is a one-line comment
1144 describing the contents of the file. Only one upload file may be open at a
1145 time. Possible return codes are:
1148 ERROR+NOT_HERE (no directory in this room)
1149 ERROR+FILE_NOT_FOUND (a name must be specified)
1150 ERROR (miscellaneous errors)
1151 ERROR+ALREADY_EXISTS (a file with the same name already exists)
1154 If OK is returned, the command has succeeded and writes may be performed.
1157 UCLS (CLoSe the Upload file)
1159 Close the file opened with UOPN. An argument of "1" should be passed to
1160 this command to close and save the file; otherwise, the transfer will be
1161 considered aborted and the file will be deleted. This command returns OK
1162 if the operation succeeded or ERROR if it did not.
1165 WRIT (WRITe to the upload file)
1167 If an upload file is open, this command may be used to write to it. The
1168 argument passed to this command is the number of bytes the client wishes to
1169 transmit. An ERROR code will be returned if the operation cannot be
1172 If the operation can be performed, SEND_BINARY will be returned, followed
1173 by the number of bytes the server is expecting. The client must then transmit
1174 exactly that number of bytes. Note that in the current implementation, the
1175 number of bytes the server is expecting will always be the number of bytes
1176 the client requested to transmit, but the client software should never assume
1177 that this will always happen, in case changes are made later.
1180 QUSR (Query for a USeR)
1182 This command is used to check to see if a particular user exists. The only
1183 argument to this command is the name of the user being searched for. If
1184 the user exists, OK is returned, along with the name of the user in the userlog
1185 (so the client software can learn the correct upper/lower casing of the name
1186 if necessary). If the user does not exist, ERROR+NO_SUCH_USER is returned.
1187 No login or current room is required to utilize this command.
1190 OIMG (Open an IMaGe file)
1192 Open an image (graphics) file for downloading. Once opened, the file can be
1193 read as if it were a download file. This implies that an image and a download
1194 cannot be opened at the same time. OIMG returns the same result codes as OPEN.
1196 All images will be in GIF (Graphics Interchange Format). In the case of
1197 Citadel/UX, the server will convert the supplied filename to all lower case,
1198 append the characters ".gif" to the filename, and look for it in the "images"
1199 subdirectory. As with the MESG command, there are several "well known"
1200 images which are likely to exist on most servers:
1202 hello - "Welcome" graphics to be displayed alongside MESG "hello"
1203 goodbye - Logoff banner graphics to be displayed alongside MESG "goodbye"
1204 background - Background image (usually tiled) for graphical clients
1206 The following "special" image names are defined in Citadel/UX server version
1209 _userpic_ - Picture of a user (send the username as the second argument)
1210 _floorpic_ - A graphical floor label (send the floor number as the second
1211 argument). Clients which request a floor picture will display
1212 the picture *instead* of the floor name.
1213 _roompic_ - A graphic associated with the *current* room. Clients which
1214 request a room picture will display the picture in *addition*
1215 to the room name (i.e. it's used for a room banner, as
1216 opposed to the floor picture's use in a floor listing).
1219 NETP (authenticate as network session with system NET Password)
1221 This command is used by client software to identify itself as a transport
1222 session for IGnet/Open BBS to BBS networking. It should be called with
1223 two arguments: the node name of the calling system, and the system net
1224 password for the server. If the authentication succeeds, NETP will return
1225 OK, otherwise, it returns ERROR.
1228 NUOP (Network Upload OPen file)
1230 Open a network spool file for uploading. The client must have already
1231 identified itself as a network session using the NETP command. If the command
1232 returns OK, the client may begin transmitting IGnet/Open spool data using
1233 a series of WRIT commands. When a UCLS command is issued, the spooled data
1234 is entered into the BBS if the argument to UCLS is 1 or discarded if the
1235 argument to UCLS is 0. If the client has not authenticated itself with a
1236 NETP command, ERROR+HIGHER_ACCESS_REQUIRED will be returned.
1239 NDOP (Network Download OPen file)
1241 Open a network spool file for downloading. The client must have already
1242 identified itself as a network session using the NETP command. If the command
1243 returns OK, the client may begin receiving IGnet/Open spool data using
1244 a series of READ commands. When a CLOS command is issued, the spooled data
1245 is deleted from the server and may not be read again. If the client has not
1246 authenticated itself with a NETP command, ERROR+HIGHER_ACCESS_REQUIRED will
1250 LFLR (List all known FLooRs)
1252 On systems supporting floors, this command lists all known floors. The
1253 command accepts no parameters. It will return ERROR+NOT_LOGGED_IN if no
1254 user is logged in. Otherwise it returns LISTING_FOLLOWS and a list of
1255 the available floors, each line consisting of three fields:
1257 1. The floor number associated with the floor
1258 2. The name of the floor
1259 3. Reference count (number of rooms on this floor)
1262 CFLR (Create a new FLooR)
1264 This command is used to create a new floor. It should be passed two
1265 arguments: the name of the new floor to be created, and a 1 or 0 depending
1266 on whether the client is actually creating a floor or merely checking to
1267 see if it has permission to create the floor. The user must be logged in
1268 and have Aide privileges to create a floor.
1270 If the command succeeds, it will return OK followed by the floor number
1271 associated with the new floor. Otherwise, it will return ERROR (plus perhaps
1272 HIGHER_ACCESS_REQUIRED, ALREADY_EXISTS, or INVALID_FLOOR_OPERATION)
1273 followed by a description of why the command failed.
1278 This command is used to delete a floor. It should be passed two
1279 argument: the *number* of the floor to be deleted, and a 1 or 0 depending
1280 on whether the client is actually deleting the floor or merely checking to
1281 see if it has permission to delete the floor. The user must be logged in
1282 and have Aide privileges to delete a floor.
1284 Floors that contain rooms may not be deleted. If there are rooms on a floor,
1285 they must be either deleted or moved to different floors first. This implies
1286 that the Main Floor (floor 0) can never be deleted, since Lobby>, Mail>, and
1287 Aide> all reside on the Main Floor and cannot be deleted.
1289 If the command succeeds, it will return OK. Otherwise it will return
1290 ERROR (plus perhaps HIGHER_ACCESS_REQUIRED or INVALID_FLOOR_OPERATION)
1291 followed by a description of why the command failed.
1296 Edit the parameters of a floor. The client may pass one or more parameters
1299 1. The number of the floor to be edited
1300 2. The desired new name
1302 More parameters may be added in the future. Any parameters not passed to
1303 the server will remain unchanged. A minimal command would be EFLR and a
1304 floor number -- which would do nothing. EFLR plus the floor number plus a
1305 floor name would change the floor's name.
1307 If the command succeeds, it will return OK. Otherwise it will return
1308 ERROR (plus perhaps HIGHER_ACCESS_REQUIRED or INVALID_FLOOR_OPERATION)
1311 IDEN (IDENtify the client software)
1313 The client software has the option to identify itself to the server.
1314 Currently, the server does nothing with this information except to write
1315 it to the syslog to satisfy the system administrator's curiosity. Other
1316 uses might become apparent in the future.
1318 The IDEN command should contain five fields: a developer ID number (same as
1319 the server developer ID numbers in the INFO command -- please obtain one if
1320 you are a new developer), a client ID number (which does not have to be
1321 globally unique - only unique within the domain of the developer number),
1322 a version number, a free-form text string describing the client, and the name
1323 of the host the user is located at.
1325 It is up to the server to determine whether to accept the host name or to
1326 use the host name it has detected itself. Generally, if the client is
1327 running on a trusted host (either localhost or a well-known publically
1328 accessible client) it should use the host name transmitted by IDEN,
1329 otherwise it should use the host name it has detected itself.
1331 IDEN always returns OK, but since that's the only way it ever returns
1332 there's no point in checking the result code.
1335 IPGM (identify as an Internal ProGraM)
1337 IPGM is a low-level command that should not be used by normal user clients.
1338 It is used for various utilities to communicate with the server on the same
1339 host. For example, the "sendcommand" utility logs onto the server as an
1340 internal program in order to run arbitrary server commands. Since user clients
1341 do not utilize this command (or any of its companion commands), developers
1342 writing Citadel-compatible servers need not implement it.
1344 The sole argument to IPGM is the system's internal program password. This
1345 password is generated by the setup program and stored in the config file.
1346 Since internal programs have access to the config file, they know the correct
1349 IPGM returns OK for a correct authentication or ERROR otherwise.
1352 CHAT (enter CHAT mode)
1354 This command functions differently from every other command in the system. It
1355 is used to implement multi-user chat. For this to function, a new transfer
1356 mode, called START_CHAT_MODE, is implemented. If a client does not support
1357 chat mode, it should never send a CHAT command!
1359 In chat mode, messages may arrive asynchronously from the server at any
1360 time. The client may send messages at any time. This allows the arrival of
1361 messages without the client having to poll for them. Arriving messages will
1362 be of the form "user|message", where the "user" portion is, of course, the
1363 name of the user sending the message, and "message" is the message text.
1365 Chat mode ends when the server says it ends. The server will signal the end
1366 of chat mode by transmitting "000" on a line by itself. When the client reads
1367 this line, it must immediately exit from chat mode without sending any
1368 further traffic to the server. The next transmission sent to the server
1369 will be a regular server command.
1371 The Citadel/UX server understands the following commands:
1372 /quit - Exit from chat mode (causes the server to do an 000 end)
1373 /who - List users currently in chat
1374 /whobbs - List users currently in chat and on the bbs
1375 /me - Do an irc-style action.
1376 /join - Join a new "room" in which all messages are only heard by
1377 people in that room.
1378 /msg - /msg <user> <msg> will send the msg to <user> only.
1379 /help - Print help information
1380 NOOP - Do nothing (silently)
1382 Any other non-empty string is treated as message text and will be broadcast
1383 to other users currently in chat.
1386 SEXP (Send EXPress messages)
1388 This is one of two commands which implement "express messages" (also known
1389 as "paging"). An express message is a near-real-time message sent from one
1390 logged in user to another. When an express message is sent, it will be
1391 displayed the next time the target user executes a PEXP or GEXP command.
1393 The SEXP command accepts two arguments: the name of the user to send the
1394 message to, and the text of the message. If the message is successfully
1395 transmitted, OK is returned. If the target user is not logged in or if
1396 anything else goes wrong, ERROR is returned.
1398 If the server supports extended paging, sending a zero-length message
1399 merely checks for the presence of the requested user without actually sending
1400 a message. Sending a message consisting solely of a "-" (hyphen) will cause
1401 the server to return SEND_LISTING if the requested user is logged in, and the
1402 client can then transmit a multi-line page.
1404 The reserved name "broadcast" may be used instead of a user name, to
1405 broadcast an express message to all users currently connected to the server.
1407 Do be aware that if an express message is transmitted to a user who is logged
1408 in using a client that does not check for express messages, the message will
1412 PEXP (Print EXPress messages) ***DEPRECATED***
1414 This command is deprecated; it will eventually disappear from the protocol and
1415 its use is not recommended. Please use the GEXP command instead.
1417 Called without any arguments, PEXP simply dumps out the contents
1418 of any waiting express messages. It returns ERROR if there is a problem,
1419 otherwise it returns LISTING_FOLLOWS followed by all messages.
1421 So how does the client know there are express messages waiting? It could
1422 execute a random PEXP every now and then. Or, it can check the byte in
1423 server return code messages, between the return code and the parameters. In
1424 much the same way as FTP uses "-" to signify a continuation, Citadel uses
1425 an "*" in this position to signify the presence of waiting express messages.
1428 EBIO (Enter BIOgraphy)
1430 Transmit to the server a free-form text file containing a little bit of
1431 information about the user for other users to browse. This is typically
1432 referred to as a 'bio' online. EBIO returns SEND_LISTING if it succeeds,
1433 after which the client is expected to transmit the file, or any of the usual
1434 ERROR codes if it fails.
1437 RBIO (Read BIOgraphy)
1439 Receive from the server a named user's bio. This command should be passed
1440 a single argument - the name of the user whose bio is requested. RBIO returns
1441 LISTING_FOLLOWS plus the bio file if the user exists and has a bio on file.
1442 The return has the following parameters: the user name, user number, access
1443 level, date of last call, times called, and messages posted. This command
1444 returns ERROR+NO_SUCH_USER if the named user does not exist.
1446 RBIO no longer considers a user with no bio on file to be an error condition.
1447 It now returns a message saying the user has no bio on file as the text of the
1448 bio. This allows newer servers to operate with older clients.
1451 STEL (enter STEaLth mode)
1453 When in "stealth mode," a user will not show up in the "Who is online"
1454 listing (the RWHO server command). Only Aides may use stealth mode. The
1455 STEL command accepts one argument: a 1 indicating that the user wishes to
1456 enter stealth mode, or a 0 indicating that the user wishes to exit stealth
1457 mode. STEL returns OK if the command succeeded, ERROR+NOT_LOGGED_IN if no
1458 user is logged in, or ERROR+HIGHER_ACCESS_REQUIRED if the user is not an Aide;
1459 followed by a 1 or 0 indicating the new state.
1461 If any value other than 1 or 0 is sent by the client, the server simply
1462 replies with 1 or 0 to indicate the current state without changing it.
1464 The STEL command also makes it so a user does not show up in the chat room
1468 LBIO (List users who have BIOs on file)
1470 This command is self-explanatory. Any user who has used EBIO to place a bio
1471 on file is listed. LBIO almost always returns LISTING_FOLLOWS followed by
1472 this listing, unless it experiences an internal error in which case ERROR
1476 MSG2 (read MeSsaGe, mode 2)
1478 MSG2 follows the same calling convention as MSG0. The difference between
1479 the two commands is that MSG2 outputs messages in standard RFC822 format
1480 rather than in Citadel/UX proprietary format.
1482 This command was implemented in order to make various gateway programs
1483 easier to implement, and to provide some sort of multimedia support in the
1484 future. Keep in mind that when this command is used, all messages will be
1485 output in fixed 80-column format.
1488 MSG3 (read MeSsaGe, mode 3 -- internal command)
1490 MSG3 is for use by internal programs only and should not be utilized by
1491 user-mode clients. It does require IPGM authentication. MSG3 follows the
1492 same calling convention as the other MSG commands, but upon success returns
1493 BINARY_FOLLOWS followed by a data block containing the _raw_ message format
1497 TERM (TERMinate another session)
1499 In a multithreaded environment, it sometimes becomes necessary to terminate
1500 a session that is unusable for whatever reason. The TERM command performs
1501 this task. Naturally, only Aides can execute TERM. The command should be
1502 called with a single argument: the session ID (obtained from an RWHO command)
1503 of the session to be terminated.
1505 TERM returns OK if the session was terminated, or ERROR otherwise. Note that
1506 a client program is prohibited from terminating the session it is currently
1512 DOWN (shut DOWN the server)
1514 This command, which may only be executed by an Aide, immediately shuts down
1515 the server. It is only implemented on servers on which such an operation is
1516 possible, such as a multithreaded Citadel engine. The server does not restart.
1517 DOWN returns OK if the user is allowed to shut down the server, in which case
1518 the client program should expect the connection to be immediately broken.
1521 SCDN (Schedule or Cancel a shutDowN)
1523 SCDN sets or clears the "scheduled shutdown" flag. Pass this command a 1 or
1524 0 to respectively set or clear the flag. When the "scheduled shutdown" flag is
1525 set, the server will be shut down when there are no longer any users logged in.
1526 Any value other than 0 or 1 will not change the flag, only report its state.
1527 No users will be kicked off the system, and in fact the server is still
1528 available for new connections. The command returns ERROR if it fails;
1529 otherwise, it returns OK followed by a number representing the current state
1533 EMSG (Enter a system MeSsaGe)
1535 This is the opposite of the MESG command - it allows the creation and editing
1536 of system messages. The only argument passed to EMSG is the name of the
1537 file being transmitted. If the file exists in any system message directory
1538 on the server it will be overwritten, otherwise a new file is created. EMSG
1539 returns SEND_LISTING on success or ERROR+HIGHER_ACCESS_REQUIRED if the user
1542 Typical client software would use MESG to retrieve any existing message into
1543 an edit buffer, then present an editor to the user and run EMSG if the changes
1547 UIMG (Upload an IMaGe file)
1549 UIMG is complemenary to OIMG; it is used to upload an image to the server.
1550 The first parameter supplied to UIMG should be 0 if the client is only checking
1551 for permission to upload, or 1 if the client is actually attempting to begin
1552 the upload operation. The second argument is the name of the file to be
1553 transmitted. In Citadel/UX, the filename is converted to all lower case,
1554 appended with the characters ".gif", and stored in the "images" directory.
1556 UIMG returns OK if the client has permission to perform the requested upload,
1557 or ERROR+HIGHER_ACCESS_REQUIRED otherwise. If the client requested to begin
1558 the operation (first parameter set to 1), an upload file is opened, and the
1559 client should begin writing to it with WRIT commands, then close it with a
1562 The supplied filename should be one of:
1564 -> _userpic_ (Server will attempt to write to the user's online photo)
1565 -> Any of the "well known" filenames described in the writeup for the
1569 HCHG (Hostname CHanGe)
1571 HCHG is a command, usable by any user, that allows a user to change their RWHO
1572 host value. This will mask a client's originating hostname from normal
1573 users; access level 6 and higher can see, in an extended wholist, the actual
1574 hostname the user originates from.
1576 The format of an HCHG command is:
1580 If a HCHG command is successful, the value OK (200) is returned.
1583 RCHG (Roomname CHanGe)
1585 RCHG is a command, usable by any user, that allows a user to change their RWHO
1586 room value. This will mask a client's roomname from normal users; access
1587 level 6 and higher can see, in an extended wholist, the actual room the user
1590 The format of an RCHG command is:
1594 If a RCHG command is successful, the value OK (200) is returned.
1597 UCHG (Username CHanGe)
1599 UCHG is an aide-level command which allows an aide to effectively change their
1600 username. If this value is blank, the user goes into stealth mode (see
1602 will show up as being from the real username in this mode, however. In
1603 addition, the RWHO listing will include both the spoofed and real usernames.
1605 The format of an UCHG command is:
1609 If a UCHG command is successful, the value OK (200) is returned.
1612 TIME (get server local TIME)
1614 TIME returns OK followed by the current time measured in seconds since
1615 00:00:00 GMT, Jan 1, 1970 (standard Unix format).
1617 This is used in allowing a client to calculate idle times.
1620 AGUP (Administrative Get User Parameters)
1621 ASUP (Administrative Set User Parameters)
1623 These commands are only executable by Aides and by server extensions running
1624 at system-level. They are used to get/set any and all parameters relating to
1625 a user account. AGUP requires only one argument: the name of the user in
1626 question. SGUP requires all of the parameters to be set. The parameters are
1627 as follows, and are common to both commands:
1631 2 - Flags (see citadel.h)
1636 7 - Timestamp of last call
1637 8 - Purge time (in days) for this user (or 0 to use system default)
1639 Upon success, AGUP returns OK followed by all these parameters, and ASUP
1640 simply returns OK. If the client has insufficient access to perform the
1641 requested operation, ERROR+HIGHER_ACCESS_REQUIRED is returned. If the
1642 requested user does not exist, ERROR+NO_SUCH_USER is returned.
1646 GPEX (Get Policy for message EXpiration)
1648 Returns the policy of the current room, floor, or site regarding the automatic
1649 purging (expiration) of messages. The following policies are available:
1650 0 - Fall back to the policy of the next higher level. If this is a room,
1651 use the floor's default policy. If this is a floor, use the system
1652 default policy. This is an invalid value for the system policy.
1653 1 - Do not purge messages automatically.
1654 2 - Purge by message count. (Requires a value: number of messages)
1655 3 - Purge by message age. (Requires a value: number of days)
1657 The format of this command is: GPEX <which>
1658 The value of <which> must be one of: "room" "floor" "site"
1660 If successful, GPEX returns OK followed by <policy>|<value>.
1664 SPEX (Set Policy for message EXpiration)
1666 Sets the policy of the current room, floor, or site regarding the automatic
1667 purging (expiration) of messages. See the writeup for the GPEX command for
1668 the list of available policies.
1670 The format of this command is: SPEX <which>|<policy>|<value>
1671 The value of <which> must be one of: "room" "floor" "site"
1673 If successful, GPEX returns OK; otherwise, an ERROR code is returned.
1677 CONF (get or set global CONFiguration options)
1679 Retrieves or sets various system-wide configuration and policy options. This
1680 command is only available to Aides. The sole parameter accepted is a command,
1681 which should be either GET or SET. If the GET command succeeds, CONF will
1682 return LISTING_FOLLOWS followed by the fields described below, one line at a
1683 time. If the SET command succeeds, CONF will return SEND_LISTING and expect
1684 the fields described below, one line at a time (don't worry about other fields
1685 being added in the future; if a 'short' configuration list is sent, the missing
1686 values at the end will be left unchanged on the system). If either command
1687 fails for any reason, ERROR is returned.
1689 The configuration lines are as follows:
1692 2. Fully qualified domain name
1693 3. Human-readable node name
1694 4. Landline telephone number of this system
1695 5. Flag (0 or 1) - creator of private room automatically becomes room aide
1696 6. Server connection idle timeout (in seconds)
1697 7. Initial access level for new users
1698 8. Flag (0 or 1) - require registration for new users
1699 9. Flag (0 or 1) - automatically move Problem User messages to twit room
1700 10. Name of twit room
1701 11. Text of <more> prompt
1702 12. Flag (0 or 1) - restrict access to Internet mail
1703 13. Geographic location of this system
1704 14. Name of the system administrator
1705 15. Number of maximum concurrent sessions allowed on the server
1706 16. Password for server-to-server networking
1707 17. Default purge time (in days) for users
1708 18. Default purge time (in days) for rooms
1709 19. Name of room to log express messages to (or a zero-length name for none)
1710 20. Access level required to create rooms
1711 21. Maximum message length which may be entered into the system
1712 22. Minimum number of worker threads
1713 23. Maximum number of worker threads
1714 24. Port number for POP3 service
1715 25. Port number for SMTP service
1717 27. Flag (0 or 1) - allow Aides to zap (forget) rooms
1718 28. Port number for IMAP service
1719 29. How often (in seconds) to run the networker
1721 CONF also accepts two additional commands: GETSYS and PUTSYS followed by an
1722 arbitrary MIME type (such as application/x-citadel-internet-config) which
1723 provides a means of storing generic configuration data in the Global System
1724 Configuration room without the need to add extra get/set commands to the
1728 EXPI (EXPIre system objects)
1730 Begins purge operations for objects which, according to site policy, are
1731 "old" and should be removed. EXPI should be called with one argument, one of:
1733 "messages" (purge old messages out of each room)
1734 "users" (purge old users from the userlog)
1735 "rooms" (remove rooms which have not been posted in for some time)
1736 "visits" (purge dereferenced user/room relationship records)
1738 EXPI returns OK (probably after a long delay while it does its work) if it
1739 succeeds; otherwise it returns an ERROR code.
1741 This command is probably temporary, until we can work some sort of scheduler
1742 into the system. It is implemented in the serv_expire module.
1746 MSG4 (read MeSsaGe, mode 4 -- enumerate MIME parts)
1748 FIXME ... do the writeup for this once it's done.
1752 OPNA (OPeN Attachment)
1754 Opens, as a download file, a component of a MIME-encoded message. The two
1755 parameters which must be passed to this command are the message number and the
1756 name of the desired section. If the message or section does not exist, an
1757 appropriate ERROR code will be returned; otherwise, if the open is successful,
1758 this command will succeed returning the same information as an OPEN command.
1761 GEXP (Get EXPress messages)
1763 This is a more sophisticated way of retrieving express messages than the old
1764 PEXP method. If there are no express messages waiting, PEXP returns ERROR;
1765 otherwise, it returns LISTING_FOLLOWS and the following arguments:
1767 0 - a boolean value telling the client whether there are any additional
1768 express messages waiting following this one
1769 1 - a Unix-style timestamp
1770 2 - flags (see server.h for more info)
1771 3 - the name of the sender
1772 4 - the node this message originated on (for future support of PIP, ICQ, etc.)
1774 The text sent to the client will be the body of the express message.
1776 So how does the client know there are express messages waiting? It could
1777 execute a random GEXP every now and then. Or, it can check the byte in
1778 server return code messages, between the return code and the parameters. In
1779 much the same way as FTP uses "-" to signify a continuation, Citadel uses
1780 an "*" in this position to signify the presence of waiting express messages.
1783 FSCK (check message base reference counts)
1785 Verify, via the long way, that all message referenmce counts are correct. If
1786 the user has permission to do this then LISTING_FOLLOWS is returned, followed
1787 by a transcript of the run. Otherwise ERROR is returned.
1790 DEXP (Disable EXPress messages)
1792 DEXP sets or clears the "disable express messages" flag. Pass this command a
1793 1 or 0 to respectively set or clear the flag. When the "disable express
1794 messages" flag is set, no one except Aides may send the user express messages.
1795 Any value other than 0 or 1 will not change the flag, only report its state.
1796 The command returns ERROR if it fails; otherwise, it returns OK followed by a
1797 number representing the current state of the flag.
1800 REQT (REQuest client Termination)
1802 Request that the specified client (or all clients) log off. Aide level
1803 access is required to run this command, otherwise ERROR+HIGHER_ACCESS_REQUIRED
1806 The REQT command accepts one parameter: the session ID of the client which
1807 should be terminated, or 0 for all clients. When successful, the REQT command
1810 It should be noted that REQT simply transmits an express message to the
1811 specified client(s) with the EM_GO_AWAY flag set. Older clients do not honor
1812 this flag, and it is certainly possible for users to re-program their client
1813 software to ignore it. Therefore the effects of the REQT command should be
1814 considered advisory only. The recommended implementation practice is to first
1815 issue a REQT command, then wait a little while (from 30 seconds up to a few
1816 minutes) for well-behaved clients to voluntarily terminate, and then issue a
1817 TERM command to forcibly disconnect the client (or perhaps a DOWN command, if
1818 you are logging off users for the purpose of shutting down the server).
1821 SEEN (set or clear the SEEN flag for a message)
1823 Beginning with version 5.80, Citadel supports the concept of setting or
1824 clearing the "seen" flag for each individual message, instead of only allowing
1825 a "last seen" pointer. In fact, the old semantics are implemented in terms
1826 of the new semantics. This command requires two arguments: the number of the
1827 message to be set, and a 1 or 0 to set or clear the "seen" bit.
1829 This command returns OK, unless the user is not logged in or a usage error
1830 occurred, in which case it returns ERROR. Please note that no checking is
1831 done on the supplied data; if the requested message does not exist, the SEEN
1832 command simply returns OK without doing anything.
1835 GTSN (GeT the list of SeeN messages)
1837 This command retrieves the list of "seen" (as opposed to unread) messages for
1838 the current room. It returns OK followed by an IMAP-format message list.
1841 SMTP (utility commands for the SMTP gateway)
1843 This command, accessible only by Aides, supports several utility operations
1844 which examine or manipulate Citadel's SMTP support. The first command argument
1845 is a subcommand telling the server what to do. The following subcommands are
1848 SMTP mx|hostname (display all MX hosts for 'hostname')
1849 SMTP runqueue (attempt immediate delivery of all messages
1850 in the outbound SMTP queue, ignoring any
1851 retry times stored there)
1854 STLS (Start Transport Layer Security)
1856 This command starts TLS on the current connection. The current
1857 implementation uses OpenSSL on both the client and server end. For future
1858 compatibility all clients must support at least TLSv1, and servers are
1859 guaranteed to support TLSv1. During TLS negotiation (see below) the server
1860 and client may agree to use a different protocol.
1862 The server returns ERROR if it does not support SSL or SSL initialization
1863 failed on the server; otherwise it returns OK. Once the server returns OK and
1864 the client has read the response, the server and client immediately negotiate
1865 TLS (in OpenSSL, using SSL_connect() on the client and SSL_accept() on the
1866 server). If negotiation fails, the server and client should attempt to resume
1867 the session unencrypted. If either end is unable to resume the session, the
1868 connection should be closed.
1870 This command may be run at any time.
1873 GTLS (Get Transport Layer Security Status)
1875 This command returns information about the current connection. The server
1876 returns OK plus several parameters if the connection is encrypted, and ERROR
1877 if the connection is not encrypted. It is primarily used for debugging. The
1878 command may be run at any time.
1880 0 - Protocol name, e.g. "SSLv3"
1881 1 - Cipher suite name, e.g. "ADH-RC4-MD5"
1882 2 - Cipher strength bits, e.g. 128
1883 3 - Cipher strength bits actually in use, e.g. 128
1886 IGAB (Initialize Global Address Book)
1888 This command creates, or re-creates, a database of Internet e-mail addresses
1889 using the vCard information in the Global Address Book room. This procedure
1890 is normally run internally when the server determines it necessary, but is
1891 also provided as a server command to be used as a troubleshooting/maintenenance
1892 tool. Only a system Aide can run the command. It returns OK on success or
1896 QDIR (Query global DIRectory)
1898 Look up an internet address in the global directory. Any logged-in user may
1899 call QDIR with one parameter, the Internet e-mail address to look up. QDIR
1900 returns OK followed by a Citadel address if there is a match, otherwise it
1901 returns ERROR+NOT_LOGGED_IN.
1904 VIEW (set the VIEW for a room)
1906 Set the preferred view for the current user in the current room. Please see
1907 views.txt for more information on views. The sole parameter for this command
1908 is the type of view requested. VIEW returns OK on success or ERROR on failure.
1911 QNOP (Quiet No OPeration)
1913 This command does nothing, similar to the NOOP command. However, unlike the
1914 NOOP command, it returns *absolutely no response* at all. The client has no
1915 way of knowing that the command executed. It is intended for sending
1916 "keepalives" in situations where a full NOOP would cause the client protocol
1919 Naturally, sending this command to a server that doesn't support it is an
1920 easy way to mess things up. Therefore, client software should first check
1921 the output of an INFO command to ensure that the server supports quiet noops.
1925 MRTG (Multi Router Traffic Grapher)
1927 Multi Router Traffic Grapher (please see http://www.mrtg.org for more info) is
1928 a tool which creates pretty graphs of network activity, usually collected from
1929 routers using SNMP. However, its ability to call external scripts has spawned
1930 a small community of people using it to graph anything which can be graphed.
1931 The MRTG command can output Citadel server activity in the format MRTG expects.
1933 This format is as follows:
1938 Line 3: uptime of system
1939 Line 4: name of system
1942 MRTG accepts two different keywords. "MRTG users" will return two variables,
1943 the number of connected users and the number of active users. "MRTG messages"
1944 will return one variable (and a zero in the second field), showing the current
1945 highest message number on the system. Any other keyword, or a missing keyword,
1946 will cause the MRTG command to return an ERROR code.
1948 Please get in touch with the Citadel developers if you wish to experiment with
1953 ASYN (ASYNchronous message support)
1955 Negotiate the use of asynchronous, or unsolicited, protocol messages. The
1956 only parameter specified should be 1 or 0 to indicate that the client can or
1957 cannot handle this type of messages. The server will reply OK followed by a
1958 1 or 0 to tell the client which mode it is now operating in.
1960 If the command is not available on the server (i.e. it returns ERROR), or
1961 if the command has not been executed by the client, it should be assumed that
1962 this mode of operation is NOT in effect.
1964 The client may also send any value other than 0 or 1 to simply cause the
1965 server to output its current state without changing it.
1967 When asynchronous protocol mode is in effect, the client MUST handle any
1968 asynchronous messages as they arrive, before doing anything else.
1973 ASYNCHRONOUS MESSAGES
1974 ---------------------
1976 When the client protocol is operating in asynchronous mode (please refer to
1977 the writeup of the ASYN command above), the following messages may arrive at
1981 901 (express message arriving)
1983 There is an express message intended for this client. When the client
1984 receives this message, it MUST act as if it just sent a GEXP command (the data
1985 following the 901 message WILL be a LISTING_FOLLOWS data transfer; in fact,
1986 the current implementation simply executes a GEXP command internally).