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IRC Documentation · Intermediate

The IRC protocol: clients, messages, and channels.

IRC is a real-time text-based communication protocol. The client sends commands to the server; the server controls rights, maintains network state, and distributes events to concerned recipients.

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Client, server, network, and IRCd #

The client is the software used for chatting. The server is a connection point. The network optionally connects several servers sharing channels and users. The IRCd is the software that runs a server. Installing the same IRCd as someone else does not place you on their network.

A channel is a discussion space within this network. Private messages typically address an identified presence by a nickname. A nickname change, a services account, and a disconnection are distinct events.

From connection to entering a channel #

  1. Establish transport and verify TLS when it is used.
  2. Negotiate useful capabilities and declare NICK/USER.
  3. Perform SASL if the network and configuration provide for it.
  4. Terminate the negotiation and wait for registration confirmation.
  5. Join an authorized channel with JOIN, then read its topic and member list.

USER provides an identifier and a realname, which is not necessarily a true civil name. PASS, when requested, concerns a login password; it is not a universal synonym for service identification. PING/PONG maintains the connection and should not be confused with a chat message.

Channels, Modes, and Operators #

ConceptsResponsibility
User ModeOwnership of a presence on the network.
Channel ModeRule or property of a discussion space.
Channel OperatorMember possessing rights within a channel.
Network Operator (IRCop)Account or presence possessing network administration permissions.
ServicesServices such as NickServ or ChanServ, integrated or separate depending on the network.

The @ symbol in a member list often indicates a channel operator, not a network administrator. PREFIX and CHANMODES in ISUPPORT describe the grammar of modes actually announced; their letters are not an identical list on all IRCd.

CTCP, DCC, History, and Media #

CTCP encapsulates certain conventions between clients within IRC messages; an /me action is typically a CTCP ACTION message. DCC offers a negotiation allowing direct communication between clients, particularly for files. These are not the same mechanisms as hosting an image on a website.

TLS protects a transport. WebSocket adapts the transport to the browser when the infrastructure allows; it does not transform IRC into a video protocol. Webcams and Dialova calls rely on a separate media layer. Histories and persistent accounts also require server, bouncer, or application features.

Sources & Verification

Examples use pseudonyms and fictional domains, except for explicitly documented connection points. Network-specific extensions and settings are noted in the text.