Client-to-client protocol

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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.^{[citation needed]} 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 newlines or the byte value 0 (NULL). 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 CTCP VERSION), or the time (via CTCP TIME), among other things. It is also used to implement the /me command (via CTCP ACTION).