Client-To-Client Protocol
Encyclopedia
Client-To-Client Protocol (CTCP) is a special type of communication between Internet Relay Chat
(IRC) clients.
CTCP is a common protocol implemented by most major IRC clients in use today. CTCP extends the original IRC protocol by allowing users to query other clients or channels, this causes all the clients in the channel to reply the CTCP, for specific information. Additionally, CTCP can be used to encode messages that the raw IRC protocol would not allow to be sent over the link, such as messages containing newline
s or the byte
value 0 (NUL). CTCP does not establish a direct connection between clients; however, it is commonly used to negotiate DCC
connections.
CTCP allows users to query a remote client about the version of the client they are using (via
A CTCP message is implemented as a
value 0x01. Additionally, characters which would not be allowed in the IRC protocol are escaped. Since a
Internet Relay Chat
Internet Relay Chat is a protocol for real-time Internet text messaging or synchronous conferencing. It is mainly designed for group communication in discussion forums, called channels, but also allows one-to-one communication via private message as well as chat and data transfer, including file...
(IRC) clients.
CTCP is a common protocol implemented by most major IRC clients in use today. CTCP extends the original IRC protocol by allowing users to query other clients or channels, this causes all the clients in the channel to reply the CTCP, for specific information. Additionally, CTCP can be used to encode messages that the raw IRC protocol would not allow to be sent over the link, such as messages containing newline
Newline
In computing, a newline, also known as a line break or end-of-line marker, is a special character or sequence of characters signifying the end of a line of text. The name comes from the fact that the next character after the newline will appear on a new line—that is, on the next line below the...
s or the byte
Byte
The byte is a unit of digital information in computing and telecommunications that most commonly consists of eight bits. Historically, a byte was the number of bits used to encode a single character of text in a computer and for this reason it is the basic addressable element in many computer...
value 0 (NUL). CTCP does not establish a direct connection between clients; however, it is commonly used to negotiate DCC
Direct Client-to-Client
Direct Client-to-Client is an IRC-related sub-protocol enabling peers to interconnect using an IRC server for handshaking in order to exchange files or perform non-relayed chats. Once established, a typical DCC session runs independently from the IRC server. Originally designed to be used with...
connections.
CTCP allows users to query a remote client about the version of the client they are using (via
CTCP VERSION), the time (via CTCP TIME), or get remote user info (via CTCP USERINFO), among other things. It is also used to implement the /me command (via CTCP ACTION).A CTCP message is implemented as a
PRIVMSG or NOTICE where the first and last characters of the message are ASCIIASCII
The American Standard Code for Information Interchange is a character-encoding scheme based on the ordering of the English alphabet. ASCII codes represent text in computers, communications equipment, and other devices that use text...
value 0x01. Additionally, characters which would not be allowed in the IRC protocol are escaped. Since a
NOTICE as the standard should not generate another NOTICE as a reply, CTCP messages are sent as PRIVMSG and the reply is implemented with a NOTICE instead of a PRIVMSG.