Internet Relay Chat

Internet Relay Chat (IRC) is a form of instant communication over the Internet that allows both one-to-one communication and group communication in discussion rooms called channels.

Table of contents

1 Technical information
2 History
3 Networks
4 Clients
5 Modern IRC
6 Miscellanea

6.1 See also
6.2 External links

Technical information

RFC 1459 describes the protocol used by the early IRC2; 2810, 2811, 2812 and 2813 describe sets of proposed IRC extensions. Most IRC implementations consist of IRC2 with various add-ons and protocol extensions, resulting in incompatibilities preventing connection of servers running different software.

IRC is an open protocol that uses TCP and optionally SSL. An IRC server can connect to other IRC servers to form an IRC network. Users access IRC networks by connecting a client to a server. There are many client and server implementations. Most IRC servers do not require users to log in, but user will have to set a nickname before being connected.

IRC is a plaintext protocol, which means that it is fully possible (though quite inconvenient) to use IRC via a raw socket connection. However, there is no well-defined character encoding for messages and nicknames, making it impossible to guarantee that non-ASCII characters are displayed the same for each participant.

The basic means of communication in an established IRC session is a channel which users can join and then send messages to, which are then relayed to all other users in the same channel. Channels which are available across an entire irc network are prepended with a '#', while ones local to a server use '&'. For example: #wikipedia.

Some users in each channel have modes that make them privileged; these are called channel operators. There are also users whose privileges extend to whole servers or networks of servers; these are called IRC Operators.

Operators can set several options to the channel they are on:

b (ban) : ban a hostmask from the channel and prevent him from coming back
i (invite) : channel can only be joined if invited by an operator
k (key) : set a password for the channel
l (limit) : limit the maximum number of users in a channel.
m (moderate) : only operator and voiced users can be read by others.
n (no outside message) : users need to be in the channel to write to it
o (operator) : to grant or remove operator status of a user
p (private) : channel does not show up in WHOIS
s (secret) : channel does not show up in LIST
t (topic) : channel topic can only be changed by an operator
v (voice) : grant or remove voice status of a user

Note that in many implementations, +p/+s are the same thing, and include the functionality of the other. There may be other channel modes depending on the server implementation.

Similary, users can get modes:

i (invisible) : render user invisible
o (operator) : irc operator flag
s (server) : allow reception of server notices
w (wallops) : allow reception of wallops

Some IRC networks use their own modes.

History

IRC was created by Jarkko Oikarinen (WiZ) in August 1988. It was created to replace a program called MUT (MultiUser Talk) on a BBS called OuluBox in Finland. Jarkko Oikarinen found inspiration in Bitnet Relay Chat which operated on the Bitnet network.

IRC gained prominence when it was used behind the Iron Curtain to report on the fall of the USSR during a media blackout. It was later used in a similar fashion by Kuwaitis during the Iraqi invasion.

Because IRC connections are unencrypted and typically span long time periods, they are an attractive target for malicious hackers. Because of this, careful security policy is necessary to ensure that an IRC network is not susceptible to an attack such as an IRC takeover war. IRC networks also k-line or g-line users or networks that tend to have a harming effect.

IRC served as an early laboratory for many kinds of Internet attacks, such as using fake ICMP unreachable messages to break TCP-based IRC connections ("nuking") to annoy users or facilitate takeovers.

Networks

Today there are several hundred running IRC networks in the world. They run various implementations of IRC servers, and are administered by various groups of IRC Operators, but the protocol exposed to IRC users is very similar, and all IRC networks can be accessed by the same client software.

The largest IRC networks have traditionally been grouped in The Big Four — a designation for networks that top the statistics. Currently this includes four networks regularly frequented by around or over hundred thousand clients, namely:

Other large networks include:

Clients

Multiple platforms : ChatZilla, Gaim, jIRC, XChat , EPIC4
Microsoft Windows : Bersirc, dIRC, HydraIRC, Klient, mIRC, pIRCh, Trillian, vIRC, XiRCON, Microsoft Comic Chat (mIRC being the most popular for IRC).
Unix(-like) : BitchX, IIRC, ircII, irssi, Kopete, KVIrc, TalkSoup (of GNUstep), Zircon, naim
MacOS : Fire, IRCle, Minerva, Snak, ShadowIRC, Colloquy
AmigaOS : AmIRC

There are also many automated clients, called "bots," short for "robot." The first 'bot was written by Greg Lindahl and provided moderation for the game of Wumpus, but most modern bots either are used to exercise operator privs (controlling channels), to annoy other users (perhaps by spamming them with lots of traffic), to answer repetitive user questions and provide help when channels are not attended, and serve as permanent points of contact for information exchange (an answering machine, file transfer, etc.).

The undernet network for example, use a bot for channel maintenance called X that offer services to ban users, keep a list of operators, and keep the topic.

Modern IRC

IRC has changed much over its life on the Internet. New server software has added a multitude of new features.

Services: Network-Operated bots to facilitate registration of nicknames and channels, sending messages for offline users and network operator functions.
Extra Modes: While the original IRC system used a set of standard user and channel modes, new servers add many new modes for such features as removing color codes from text, or obscuring a user's hostmask to protect from denial of service attacks.
Proxy Detection: Most modern servers support detection of users attempting to connect through an insecure (misconfigured or exploited) proxy, which can then be denied a connection.
Additional Commands: New commands can be such things as shorthand commands to issue commands to Services, to network operator only commands to manipulate a user's hostmask.

Miscellanea

Because major IRC servers support clients from different parts of the globe that interact in real time, UTC time is generally used for international meetings.

IRC has been described (by a quote from Bash.org) as "multiplayer notepad."