File = root:/irc/ctcpdcc.txt | Uploaded on 21/12/2002


	CTCP and DCC Protocol Questions Version 1.0 written by LGM =============================== * What does "CTCP" stand for? * Why is it called Client to Client Protocol? * How does it work? * What are the common CTCP commands? * Why don't some IRC clients support all these? * How do I send a CTCP command? * What is a CTCP flood? * How do CTCP floods work? * What about DCC? * What can I do if I want more information on CTCP? * Summary =============================== Q: What does CTCP stand for? CTCP stands for Client To Client Protocol. This is not to be confused with the CCCP ;) Q: Why is it called Client to Client Protocol? Because it is sent and interpreted by your IRC client. The IRC server has nothing to do with CTCP. It treats a CTCP message as just another /msg to someone. Unlike other commands, for example /whois. Q: How does it work? In CTCP, there are two forms of communication: COMMAND and REPLY. Commands are sent as follows: PRIVMSG ((target):^A ((command>) ((value)^A, where * ^A = ASCII Character 1 * command = CTCP command * value = value to be processed by the target's client And REPLIES in this format: NOTICE ((target):^A ((command) ((value)^A, where * ^A = ASCII Character 1 * command = CTCP command * value = value to be processed by the target's client For example, a ping of channel #xphiles would be: PRIVMSG #xphiles :^APING 866780265^A This message would be received by all the people on channel #xphiles but yourself. They would all get this: :LGM!duck@opera.iinet.net.au PRIVMSG #xphiles :^APING 866780265^A For example, a reply to this ping would be: NOTICE LGM :^APING 866780265^A This message would be received by LGM like this: :Skinner!sjm076@ppp-per-217.ca.com.au NOTICE LGM :^APING 866780265^A LGM's client would then interpret this as being a reply to a PING and process it accordingly, in this case, taking the timestamp (866780265) and subtracting it from the current timestamp. Q: What are the common CTCP commands? CLIENTINFO, ACTION, DCC, ERRMSG, FACE, FINGER, PING, SOUND, SOURCE, TIME, USERINFO, VERSION, and XDCC. Briefly, this is what each command does: CLIENTINFO -- Display valid CTCP commands for that client. ACTION -- when you type /me does this, it is actually sent as a CTCP message. However, unlike other CTCP commands, it does not require a REPLY, and none should be given. DCC -- DCC is established by CTCP, however it is not conducted over CTCP. See the section on DCC for more information on this protocol. ERRMSG -- Reply to unknown CTCP command. FACE -- Pictographic 32x32 pixel representation of user (Macintosh clients only). FINGER -- Shows idletime of client, usually with an e-mail address and message. PING -- Used to measure lag, or the time it takes for information to travel between servers. SOUND -- Causes the client(s) that receive it to play a sound file. SOURCE -- A URL where the client/script can be obtained. TIME -- Local time of recipient. USERINFO -- Shows a "witty" saying set by user. VERSION -- Replies with IRC client version. Q: Why don't some IRC clients support all these? Because they don't basically ;) However, nearly every IRC client will support CLIENTINFO, which shows what commands that client supports. Q: How do I send a CTCP command? /CTCP ((target) ((command) is implemented in nearly every IRC client. For those that it isn't, usually commands like /version ((target), /ping ((target), etc., are. The exception to this is PING, which is usually done by /ping ((target) (or /cping ((target) in ircle). Q: What is a CTCP flood? It is when someone maliciously makes your client reply to CTCP messages with the purpose of making you disconnect from the IRC server. Q: How do CTCP floods work? Most servers are set up to allow you receive more data than you can send; therefore some commands such as CLIENTINFO can be used to disconnect you. The command to make your client reply to a CLIENTINFO is 12 characters (plus source/target information), while the reply to CLIENTINFO may be 100 - 200 characters. You will be disconnected with the message "Excess Flood." Q: What about DCC? DCC is started by a CTCP command. However, once it is started, it is conducted totally independant of the IRC server. For example, to start a DCC chat connection, the originator of the request (whoever typed /dcc chat ((nick)] will send something like this: PRIVMSG ((target) :^ADCC CHAT ((type) ((longip) ((port)^A * ^A = ASCII Character 1 * type = Either Chat or Talk, but almost always Chat these days * longip = 32-bit Internet address of originator's machine * port = Port on which the originator is waitng for a DCC chat The person I want to DCC chat would get this: :LGM!duck@opera.iinet.net.au PRIVMSG SomeOne :^ADCC CHAT CHAT 3406736986 2094^A From this, their IRC client would know that the machine with address 3406736986 is ready to accept a DCC chat connection on port 2094. The IRC client of the target of the DCC chat would then establish a connection to port 2094 of machine 3406736986 if the DCC chat was accepted. DCC file sends are similar to DCC chat requests, but follow the format below: PRIVMSG ((target) :^ADCC SEND ((filename) ((longip) ((port) ((filesize)^A, where * ^A = ASCII Character 1 * filename = Name of file being sent * longip = 32-bit Internet address of originator's machine * port = Port on which the originator is waiitng for a DCC chat * filesize = Size of file being sent The person I want to send a file to would get this: :LGM!duck@opera.iinet.net.au PRIVMSG Someone :^ADCC SEND CTCP_and_DCC 3406736986 2097 4509^A From this, their IRC client would know that the machine with address 3406736986 is ready to send a file named "CTCP_and_DCC" that is 4509 bytes long on port 2097. The IRC client of the target of the DCC send would then establish a connection to port 2097 of machine 3406736986 if the DCC send was accepted. Q: What can I do if I want more information on CTCP? The Undernet Doco-Com website at http://www.doco-com.undernet.org has the real RFC for both the DCC and CTCP protocols, if you are interested in referring to these technical documents. Summary: CTCP commands are sent as privmsgs. CTCP replies are sent as notices. CTCP commands and replies are in the format of ((privmsg/notice) ((target):^A((command) ((arguments)^A. ================================================= Copyright © 1997 Undernet User Committee

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