CTCP (Client To Client Protocol) is a way of sending arbitrary data
over an IRC network, which may include bytes not allowed in standard
IRC messages. CTCPs are sent as a PRIVMSG or NOTICE, where the first
and last characters as \001
(SOH), and special bytes are escaped
by encoding them into a two-byte sequence beginning with \020
(DLE). CTCPs consist of command name (typically in upper-case)
followed by list of space-separated arguments, which may be empty.
One use of CTCPs supported by the vast majority of IRC clients today
is the ACTION command, typically invoked with /me. For example, if
the user foo
in the channel #bar
were to issue
/me dances
everyone in the channel would receive the message
:foo PRIVMSG #bar :\001ACTION dances\001
Other common uses of CTCP include requesting the name and version of
a user's IRC client, their local time, determining ping times, and
initiating file transfers (DCC).
Characters are escaped as follows:
\000
(NUL)\020 \060
("0")\012
(NL)\020 \156
("n")\015
(CR)\020 \162
("r")\020
(DLE)\020 \020
All other appearences of the escape character are errors, and are
dropped.
See http://www.irchelp.org/irchelp/rfc/ctcpspec.html for more
details.