Internet Relay Chat Protocol

Network Working Group J. Oikarinen
Request for Comments: 1459 D. Reed
May 1993

Internet Relay Chat Protocol

Status of This Memo

This memo defines an EXPerimental Protocol for the Internet
community. Discussion and suggestions for improvement are requested.
Please refer to the current edition of the "IAB Official Protocol
Standards" for the standardization state and status of this protocol.
Distribution of this memo is unlimited.

Abstract

The IRC protocol was developed over the last 4 years since it was
first implemented as a means for users on a BBS to chat amongst
themselves. Now it supports a world-wide network of servers and
clients, and is stringing to cope with growth. Over the past 2 years,
the average number of users connected to the main IRC network has
grown by a factor of 10.

The IRC protocol is a text-based protocol, with the simplest client
being any socket program capable of connecting to the server.

Table of Contents

1. INTRODUCTION ............................................... 4
1.1 Servers ................................................ 4
1.2 Clients ................................................ 5
1.2.1 Operators .......................................... 5
1.3 Channels ................................................ 5
1.3.1 Channel Operators .................................... 6
2. THE IRC SPECIFICATION ....................................... 7
2.1 Overview ................................................ 7
2.2 Character codes ......................................... 7
2.3 Messages ................................................ 7
2.3.1 Message format in 'pseudo' BNF .................... 8
2.4 Numeric replies ......................................... 10
3. IRC Concepts ................................................ 10
3.1 One-to-one communication ................................ 10
3.2 One-to-many ............................................. 11
3.2.1 To a list .......................................... 11
3.2.2 To a group (channel) ............................... 11
3.2.3 To a host/server mask .............................. 12
3.3 One to all .............................................. 12

3.3.1 Client to Client ................................... 12
3.3.2 Clients to Server .................................. 12
3.3.3 Server to Server ................................... 12
4. MESSAGE DETAILS ............................................. 13
4.1 Connection Registration ................................. 13
4.1.1 PassWord message ................................... 14
4.1.2 Nickname message ................................... 14
4.1.3 User message ....................................... 15
4.1.4 Server message ..................................... 16
4.1.5 Operator message ................................... 17
4.1.6 Quit message ....................................... 17
4.1.7 Server Quit message ................................ 18
4.2 Channel operations ...................................... 19
4.2.1 Join message ....................................... 19
4.2.2 Part message ....................................... 20
4.2.3 Mode message ....................................... 21
4.2.3.1 Channel modes ................................. 21
4.2.3.2 User modes .................................... 22
4.2.4 Topic message ...................................... 23
4.2.5 Names message ...................................... 24
4.2.6 List message ....................................... 24
4.2.7 Invite message ..................................... 25
4.2.8 Kick message ....................................... 25
4.3 Server queries and commands ............................. 26
4.3.1 Version message .................................... 26
4.3.2 Stats message ...................................... 27
4.3.3 Links message ...................................... 28
4.3.4 Time message ....................................... 29
4.3.5 Connect message .................................... 29
4.3.6 Trace message ...................................... 30
4.3.7 Admin message ...................................... 31
4.3.8 Info message ....................................... 31
4.4 Sending messages ........................................ 32
4.4.1 Private messages ................................... 32
4.4.2 Notice messages .................................... 33
4.5 User-based queries ...................................... 33
4.5.1 Who query .......................................... 33
4.5.2 Whois query ........................................ 34
4.5.3 Whowas message ..................................... 35
4.6 Miscellaneous messages .................................. 35
4.6.1 Kill message ....................................... 36
4.6.2 Ping message ....................................... 37
4.6.3 Pong message ....................................... 37
4.6.4 Error message ...................................... 38
5. OPTIONAL MESSAGES ........................................... 38
5.1 Away message ............................................ 38
5.2 Rehash command .......................................... 39
5.3 Restart command ......................................... 39

5.4 Summon message .......................................... 40
5.5 Users message ........................................... 40
5.6 Operwall command ........................................ 41
5.7 Userhost message ........................................ 42
5.8 Ison message ............................................ 42
6. REPLIES ..................................................... 43
6.1 Error Replies ........................................... 43
6.2 Command responses ....................................... 48
6.3 Reserved numerics ....................................... 56
7. Client and server authentication ............................ 56
8. Current Implementations Details ............................. 56
8.1 Network protocol: TCP ................................... 57
8.1.1 Support of Unix sockets ............................ 57
8.2 Command Parsing ......................................... 57
8.3 Message delivery ........................................ 57
8.4 Connection 'Liveness' ................................... 58
8.5 Establishing a server-client connection ................. 58
8.6 Establishing a server-server connection ................. 58
8.6.1 State information exchange when connecting ......... 59
8.7 Terminating server-client connections ................... 59
8.8 Terminating server-server connections ................... 59
8.9 Tracking nickname changes ............................... 60
8.10 Flood control of clients ............................... 60
8.11 Non-blocking lookups ................................... 61
8.11.1 Hostname (DNS) lookups ............................ 61
8.11.2 Username (Ident) lookups .......................... 61
8.12 Configuration file ..................................... 61
8.12.1 Allowing clients to connect ....................... 62
8.12.2 Operators ......................................... 62
8.12.3 Allowing servers to connect ....................... 62
8.12.4 Administrivia ..................................... 63
8.13 Channel membership ..................................... 63
9. Current problems ............................................ 63
9.1 Scalability ............................................. 63
9.2 Labels .................................................. 63
9.2.1 Nicknames .......................................... 63
9.2.2 Channels ........................................... 64
9.2.3 Servers ............................................ 64
9.3 Algorithms .............................................. 64
10. Support and availability ................................... 64
11. Security Considerations .................................... 65
12. Authors' Addresses ......................................... 65

1. INTRODUCTION

The IRC (Internet Relay Chat) protocol has been designed over a
number of years for use with text based conferencing. This document
describes the current IRC protocol.

The IRC protocol has been developed on systems using the TCP/IP
network protocol, although there is no requirement that this remain
the only sphere in which it operates.

IRC itself is a teleconferencing system, which (through the use of
the client-server model) is well-suited to running on many machines
in a distributed fashion. A typical setup involves a single process
(the server) forming a central point for clients (or other servers)
to connect to, performing the required message delivery/multiplexing
and other functions.

1.1 Servers

The server forms the backbone of IRC, providing a point to which
clients may connect to to talk to each other, and a point for other
servers to connect to, forming an IRC network. The only network
configuration allowed for IRC servers is that of a spanning tree [see
Fig. 1] where each server acts as a central node for the rest of the
net it sees.

[ Server 15 ] [ Server 13 ] [ Server 14]
/ \ /
/ \ /
[ Server 11 ] ------ [ Server 1 ] [ Server 12]
/ \ /
/ \ /
[ Server 2 ] [ Server 3 ]
/ \ \
/ \ \
[ Server 4 ] [ Server 5 ] [ Server 6 ]
/ \ /
/ \ /
/ \____ /
/ \ /
[ Server 7 ] [ Server 8 ] [ Server 9 ] [ Server 10 ]

:
[ etc. ]
:

[ Fig. 1. Format of IRC server network ]

1.2 Clients

A client is anything connecting to a server that is not another
server. Each client is distinguished from other clients by a unique
nickname having a maximum length of nine (9) characters. See the
protocol grammar rules for what may and may not be used in a
nickname. In addition to the nickname, all servers must have the
following information about all clients: the real name of the host
that the client is running on, the username of the client on that
host, and the server to which the client is connected.

1.2.1 Operators

To allow a reasonable amount of order to be kept within the IRC
network, a special class of clients (operators) is allowed to perform
general maintenance functions on the network. Although the powers
granted to an operator can be considered as 'dangerous', they are
nonetheless required. Operators should be able to perform basic
network tasks such as disconnecting and reconnecting servers as
needed to prevent long-term use of bad network routing. In
recognition of this need, the protocol discussed herein provides for
operators only to be able to perform such functions. See sections
4.1.7 (SQUIT) and 4.3.5 (CONNECT).

A more controversial power of operators is the ability to remove a
user from the connected network by 'force', i.e. operators are able
to close the connection between any client and server. The
justification for this is delicate since its abuse is both
destructive and annoying. For further details on this type of
action, see section 4.6.1 (KILL).

1.3 Channels

A channel is a named group of one or more clients which will all
receive messages addressed to that channel. The channel is created
implicitly when the first client joins it, and the channel ceases to
exist when the last client leaves it. While channel exists, any
client can reference the channel using the name of the channel.

Channels names are strings (beginning with a '&' or '#' character) of
length up to 200 characters. Apart from the the requirement that the
first character being either '&' or '#'; the only restriction on a
channel name is that it may not contain any spaces (' '), a control G
(^G or ASCII 7), or a comma (',' which is used as a list item
separator by the protocol).

There are two types of channels allowed by this protocol. One is a
distributed channel which is known to all the servers that are

connected to the network. These channels are marked by the first
character being a only clients on the server where it exists may join
it. These are distinguished by a leading '&' character. On top of
these two types, there are the various channel modes available to
alter the characteristics of individual channels. See section 4.2.3
(MODE command) for more details on this.

To create a new channel or become part of an existing channel, a user
is required to JOIN the channel. If the channel doesn't exist prior
to joining, the channel is created and the creating user becomes a
channel operator. If the channel already exists, whether or not your
request to JOIN that channel is honoured depends on the current modes
of the channel. For example, if the channel is invite-only, (+i),
then you may only join if invited. As part of the protocol, a user
may be a part of several channels at once, but a limit of ten (10)
channels is recommended as being ample for both experienced and
novice users. See section 8.13 for more information on this.

If the IRC network becomes disjoint because of a split between two
servers, the channel on each side is only composed of those clients
which are connected to servers on the respective sides of the split,
possibly ceasing to exist on one side of the split. When the split
is healed, the connecting servers announce to each other who they
think is in each channel and the mode of that channel. If the
channel exists on both sides, the JOINs and MODEs are interpreted in
an inclusive manner so that both sides of the new connection will
agree about which clients are in the channel and what modes the
channel has.

1.3.1 Channel Operators

The channel operator (also referred to as a "chop" or "chanop") on a
given channel is considered to 'own' that channel. In recognition of
this status, channel operators are endowed with certain powers which
enable them to keep control and some sort of sanity in their channel.
As an owner of a channel, a channel operator is not required to have
reasons for their actions, although if their actions are generally
antisocial or otherwise abusive, it might be reasonable to ask an IRC
operator to intervene, or for the usersjust leave and go elsewhere
and form their own channel.

The commands which may only be used by channel operators are:

KICK - Eject a client from the channel
MODE - Change the channel's mode
INVITE - Invite a client to an invite-only channel (mode +i)
TOPIC - Change the channel topic in a mode +t channel

A channel operator is identified by the '@' symbol next to their
nickname whenever it is associated with a channel (ie replies to the
NAMES, WHO and WHOIS commands).

2. The IRC Specification

2.1 Overview

The protocol as described herein is for use both with server to
server and client to server connections. There are, however, more
restrictions on client connections (which are considered to be
untrustworthy) than on server connections.

2.2 Character codes

No specific character set is specified. The protocol is based on a a
set of codes which are composed of eight (8) bits, making up an
octet. Each message may be composed of any number of these octets;
however, some octet values are used for control codes which act as
message delimiters.

Regardless of being an 8-bit protocol, the delimiters and keywords
are such that protocol is mostly usable from USASCII terminal and a
telnet connection.

Because of IRC's scandanavian origin, the characters {} are
considered to be the lower case equivalents of the characters []\,
respectively. This is a critical issue when determining the
equivalence of two nicknames.

2.3 Messages

Servers and clients send eachother messages which may or may not
generate a reply. If the message contains a valid command, as
described in later sections, the client should expect a reply as
specified but it is not advised to wait forever for the reply; client
to server and server to server communication is essentially
asynchronous in nature.

Each IRC message may consist of up to three main parts: the prefix
(optional), the command, and the command parameters (of which there
may be up to 15). The prefix, command, and all parameters are
separated by one (or more) ASCII space character(s) (0x20).

The presence of a prefix is indicated with a single leading ASCII
colon character (':', 0x3b), which must be the first character of the
message itself. There must be no gap (whitespace) between the colon
and the prefix. The prefix is used by servers to indicate the true

origin of the message. If the prefix is missing from the message, it
is assumed to have originated from the connection from which it was
received. Clients should not use prefix when sending a message from
themselves; if they use a prefix, the only valid prefix is the
registered nickname associated with the client. If the source
identified by the prefix cannot be found from the server's internal
database, or if the source is registered from a different link than
from which the message arrived, the server must ignore the message
silently.

The command must either be a valid IRC command or a three (3) digit
number represented in ASCII text.

IRC messages are always lines of characters terminated with a CR-LF
(Carriage Return - Line Feed) pair, and these messages shall not
exceed 512 characters in length, counting all characters including
the trailing CR-LF. Thus, there are 510 characters maximum allowed
for the command and its parameters. There is no provision for
continuation message lines. See section 7 for more details about
current implementations.

2.3.1 Message format in 'pseudo' BNF

The protocol messages must be extracted from the contiguous stream of
octets. The current solution is to designate two characters, CR and
LF, as message separators. Empty messages are silently ignored,
which permits use of the sequence CR-LF between messages
without extra problems.

The extracted message is parsed into the components <prefix>,
<command> and list of parameters matched either by <middle> or
<trailing> components.

The BNF representation for this is:

<message> ::= [':' <prefix> <SPACE> ] <command> <params> <crlf>
<prefix> ::= <servername> <nick> [ '!' <user> ] [ '@' <host> ]
<command> ::= <letter> { <letter> } <number> <number> <number>
<SPACE> ::= ' ' { ' ' }
<params> ::= <SPACE> [ ':' <trailing> <middle> <params> ]

<middle> ::= <Any *non-empty* sequence of octets not including SPACE
or NUL or CR or LF, the first of which may not be ':'>
<trailing> ::= <Any, possibly *empty*, sequence of octets not including
NUL or CR or LF>

<crlf> ::= CR LF

NOTES:

1) <SPACE> is consists only of SPACE character(s) (0x20).
Specially notice that TABULATION, and all other control
characters are considered NON-WHITE-SPACE.

2) After extracting the parameter list, all parameters are equal,
whether matched by <middle> or <trailing>. <Trailing> is just
a syntactic trick to allow SPACE within parameter.

3) The fact that CR and LF cannot appear in parameter strings is
just artifact of the message framing. This might change later.

4) The NUL character is not special in message framing, and
basically could end up inside a parameter, but as it would
cause extra complexities in normal C string handling. Therefore
NUL is not allowed within messages.

5) The last parameter may be an empty string.

6) Use of the extended prefix (['!' <user> ] ['@' <host> ]) must
not be used in server to server communications and is only
intended for server to client messages in order to provide
clients with more useful information about who a message is
from without the need for additional queries.

Most protocol messages specify additional semantics and syntax for
the extracted parameter strings dictated by their position in the
list. For example, many server commands will assume that the first
parameter after the command is the list of targets, which can be
described with:

<target> ::= <to> [ "," <target> ]
<to> ::= <channel> <user> '@' <servername> <nick> <mask>
<channel> ::= ('#' '&') <chstring>
<servername> ::= <host>
<host> ::= see RFC952 [DNS:4] for details on allowed hostnames
<nick> ::= <letter> { <letter> <number> <special> }
<mask> ::= ('#' '$') <chstring>
<chstring> ::= <any 8bit code except SPACE, BELL, NUL, CR, LF and
comma (',')>

Other parameter syntaxes are:

<user> ::= <nonwhite> { <nonwhite> }
<letter> ::= 'a' ... 'z' 'A' ... 'Z'
<number> ::= '0' ... '9'
<special> ::= '-' '[' ']' '\' '`' '^' '{' '}'

<nonwhite> ::= <any 8bit code except SPACE (0x20), NUL (0x0), CR
(0xd), and LF (0xa)>

2.4 Numeric replies

Most of the messages sent to the server generate a reply of some
sort. The most common reply is the numeric reply, used for both
errors and normal replies. The numeric reply must be sent as one
message consisting of the sender prefix, the three digit numeric, and
the target of the reply. A numeric reply is not allowed to originate
from a client; any such messages received by a server are silently
dropped. In all other respects, a numeric reply is just like a normal
message, except that the keyword is made up of 3 numeric digits
rather than a string of letters. A list of different replies is
supplied in section 6.

3. IRC Concepts.

This section is devoted to describing the actual concepts behind the
organization of the IRC protocol and how the current
implementations deliver different classes of messages.

1--\
A D---4
2--/ \ /
B----C
/ \
3 E

Servers: A, B, C, D, E Clients: 1, 2, 3, 4

[ Fig. 2. Sample small IRC network ]

3.1 One-to-one communication

Communication on a one-to-one basis is usually only performed by
clients, since most server-server traffic is not a result of servers
talking only to each other. To provide a secure means for clients to
talk to each other, it is required that all servers be able to send a
message in exactly one direction along the spanning tree in order to
reach any client. The path of a message being delivered is the
shortest path between any two points on the spanning tree.

The following examples all refer to Figure 2 above.

Example 1:
A message between clients 1 and 2 is only seen by server A, which
sends it straight to client 2.

Example 2:
A message between clients 1 and 3 is seen by servers A & B, and
client 3. No other clients or servers are allowed see the message.

Example 3:
A message between clients 2 and 4 is seen by servers A, B, C & D
and client 4 only.

3.2 One-to-many

The main goal of IRC is to provide a forum which allows easy and
efficient conferencing (one to many conversations). IRC offers
several means to achieve this, each serving its own purpose.

3.2.1 To a list

The least efficient style of one-to-many conversation is through
clients talking to a 'list' of users. How this is done is almost
self explanatory: the client gives a list of destinations to which
the message is to be delivered and the server breaks it up and
dispatches a separate copy of the message to each given destination.
This isn't as efficient as using a group since the destination list
is broken up and the dispatch sent without checking to make sure
duplicates aren't sent down each path.

3.2.2 To a group (channel)

In IRC the channel has a role equivalent to that of the multicast
group; their existence is dynamic (coming and going as people join
and leave channels) and the actual conversation carried out on a
channel is only sent to servers which are supporting users on a given
channel. If there are multiple users on a server in the same
channel, the message text is sent only once to that server and then
sent to each client on the channel. This action is then repeated for
each client-server combination until the original message has fanned
out and reached each member of the channel.

The following examples all refer to Figure 2.

Example 4:
Any channel with 1 client in it. Messages to the channel go to the
server and then nowhere else.

Example 5:
2 clients in a channel. All messages traverse a path as if they
were private messages between the two clients outside a channel.

Example 6:
Clients 1, 2 and 3 in a channel. All messages to the channel are
sent to all clients and only those servers which must be traversed
by the message if it were a private message to a single client. If
client 1 sends a message, it goes back to client 2 and then via
server B to client 3.

3.2.3 To a host/server mask

To provide IRC operators with some mechanism to send messages to a
large body of related users, host and server mask messages are
provided. These messages are sent to users whose host or server
information match that of the mask. The messages are only sent to
locations where users are, in a fashion similar to that of channels.

3.3 One-to-all

The one-to-all type of message is better described as a broadcast
message, sent to all clients or servers or both. On a large network
of users and servers, a single message can result in a lot of traffic
being sent over the network in an effort to reach all of the desired
destinations.

For some messages, there is no option but to broadcast it to all
servers so that the state information held by each server is
reasonably consistent between servers.

3.3.1 Client-to-Client

There is no class of message which, from a single message, results in
a message being sent to every other client.

3.3.2 Client-to-Server

Most of the commands which result in a change of state information
(such as channel membership, channel mode, user status, etc) must be
sent to all servers by default, and this distribution may not be
changed by the client.

3.3.3 Server-to-Server.

While most messages between servers are distributed to all 'other'
servers, this is only required for any message that affects either a
user, channel or server. Since these are the basic items found in

IRC, nearly all messages originating from a server are broadcast to
all other connected servers.

4. Message details

On the following pages are descriptions of each message recognized by
the IRC server and client. All commands described in this section
must be implemented by any server for this protocol.

Where the reply ERR_NOSUCHSERVER is listed, it means that the
<server> parameter could not be found. The server must not send any
other replies after this for that command.

The server to which a client is connected is required to parse the
complete message, returning any appropriate errors. If the server
encounters a fatal error while parsing a message, an error must be
sent back to the client and the parsing terminated. A fatal error
may be considered to be incorrect command, a destination which is
otherwise unknown to the server (server, nick or channel names fit
this category), not enough parameters or incorrect privileges.

If a full set of parameters is presented, then each must be checked
for validity and appropriate responses sent back to the client. In
the case of messages which use parameter lists using the comma as an
item separator, a reply must be sent for each item.

In the examples below, some messages appear using the full format:

:Name COMMAND parameter list

Such examples represent a message from "Name" in transit between
servers, where it is essential to include the name of the original
sender of the message so remote servers may send back a reply along
the correct path.

4.1 Connection Registration

The commands described here are used to register a connection with an
IRC server as either a user or a server as well as correctly
disconnect.

A "PASS" command is not required for either client or server
connection to be registered, but it must precede the server message
or the latter of the NICK/USER combination. It is strongly
recommended that all server connections have a password in order to
give some level of security to the actual connections. The
recommended order for a client to register is as follows:

1. Pass message
2. Nick message
3. User message

4.1.1 Password message

Command: PASS
Parameters: <password>

The PASS command is used to set a 'connection password'. The
password can and must be set before any attempt to register the
connection is made. Currently this requires that clients send a PASS
command before sending the NICK/USER combination and servers *must*
send a PASS command before any SERVER command. The password supplied
must match the one contained in the C/N lines (for servers) or I
lines (for clients). It is possible to send multiple PASS commands
before registering but only the last one sent is used for
verification and it may not be changed once registered. Numeric
Replies:

ERR_NEEDMOREPARAMS ERR_ALREADYREGISTRED

Example:

PASS secretpasswordhere

4.1.2 Nick message

Command: NICK
Parameters: <nickname> [ <hopcount> ]

NICK message is used to give user a nickname or change the previous
one. The <hopcount> parameter is only used by servers to indicate
how far away a nick is from its home server. A local connection has
a hopcount of 0. If supplied by a client, it must be ignored.

If a NICK message arrives at a server which already knows about an
identical nickname for another client, a nickname collision occurs.
As a result of a nickname collision, all instances of the nickname
are removed from the server's database, and a KILL command is issued
to remove the nickname from all other server's database. If the NICK
message causing the collision was a nickname change, then the
original (old) nick must be removed as well.

If the server recieves an identical NICK from a client which is
directly connected, it may issue an ERR_NICKCOLLISION to the local
client, drop the NICK command, and not generate any kills.

Numeric Replies:

ERR_NONICKNAMEGIVEN ERR_ERRONEUSNICKNAME
ERR_NICKNAMEINUSE ERR_NICKCOLLISION

Example:

NICK Wiz ; Introducing new nick "Wiz".

:WiZ NICK Kilroy ; WiZ changed his nickname to Kilroy.

4.1.3 User message

Command: USER
Parameters: <username> <hostname> <servername> <realname>

The USER message is used at the beginning of connection to specify
the username, hostname, servername and realname of s new user. It is
also used in communication between servers to indicate new user
arriving on IRC, since only after both USER and NICK have been
received from a client does a user become registered.

Between servers USER must to be prefixed with client's NICKname.
Note that hostname and servername are normally ignored by the IRC
server when the USER command comes from a directly connected client
(for security reasons), but they are used in server to server
communication. This means that a NICK must always be sent to a
remote server when a new user is being introduced to the rest of the
network before the accompanying USER is sent.

It must be noted that realname parameter must be the last parameter,
because it may contain space characters and must be prefixed with a
colon (':') to make sure this is recognised as such.

Since it is easy for a client to lie about its username by relying
solely on the USER message, the use of an "Identity Server" is
recommended. If the host which a user connects from has such a
server enabled the username is set to that as in the reply from the
"Identity Server".

Numeric Replies:

ERR_NEEDMOREPARAMS ERR_ALREADYREGISTRED

Examples:

USER guest tolmoon tolsun :Ronnie Reagan

; User registering themselves with a
username of "guest" and real name
"Ronnie Reagan".

:testnick USER guest tolmoon tolsun :Ronnie Reagan
; message between servers with the
nickname for which the USER command
belongs to

4.1.4 Server message

Command: SERVER
Parameters: <servername> <hopcount> <info>

The server message is used to tell a server that the other end of a
new connection is a server. This message is also used to pass server
data over whole net. When a new server is connected to net,
information about it be broadcast to the whole network. <hopcount>
is used to give all servers some internal information on how far away
all servers are. With a full server list, it would be possible to
construct a map of the entire server tree, but hostmasks prevent this
from being done.

The SERVER message must only be accepted from either (a) a connection
which is yet to be registered and is attempting to register as a
server, or (b) an existing connection to another server, in which
case the SERVER message is introducing a new server behind that
server.

Most errors that occur with the receipt of a SERVER command result in
the connection being terminated by the destination host (target
SERVER). Error replies are usually sent using the "ERROR" command
rather than the numeric since the ERROR command has several useful
properties which make it useful here.

If a SERVER message is parsed and attempts to introduce a server
which is already known to the receiving server, the connection from
which that message must be closed (following the correct procedures),
since a duplicate route to a server has formed and the acyclic nature
of the IRC tree broken.

Numeric Replies:

ERR_ALREADYREGISTRED

Example:

SERVER test.oulu.fi 1 :[tolsun.oulu.fi] Experimental server
; New server test.oulu.fi introducing
itself and attempting to register. The
name in []'s is the hostname for the
host running test.oulu.fi.

:tolsun.oulu.fi SERVER csd.bu.edu 5 :BU Central Server
; Server tolsun.oulu.fi is our uplink
for csd.bu.edu which is 5 hops away.

4.1.5 Oper

Command: OPER
Parameters: <user> <password>

OPER message is used by a normal user to oBTain operator privileges.
The combination of <user> and <password> are required to gain
Operator privileges.

If the client sending the OPER command supplies the correct password
for the given user, the server then informs the rest of the network
of the new operator by issuing a "MODE +o" for the clients nickname.

The OPER message is client-server only.

Numeric Replies:

ERR_NEEDMOREPARAMS RPL_YOUREOPER
ERR_NOOPERHOST ERR_PASSWDMISMATCH

Example:

OPER foo bar ; Attempt to register as an operator
using a username of "foo" and "bar" as
the password.

4.1.6 Quit

Command: QUIT
Parameters: [<Quit message>]

A client session is ended with a quit message. The server must close
the connection to a client which sends a QUIT message. If a "Quit
Message" is given, this will be sent instead of the default message,
the nickname.

When netsplits (disconnecting of two servers) occur, the quit message

is composed of the names of two servers involved, separated by a
space. The first name is that of the server which is still connected
and the second name is that of the server that has become
disconnected.

If, for some other reason, a client connection is closed without the
client issuing a QUIT command (e.g. client dies and EOF occurs
on socket), the server is required to fill in the quit message with
some sort of message reflecting the nature of the event which
caused it to happen.

Numeric Replies:

None.

Examples:

QUIT :Gone to have lunch ; Preferred message format.

4.1.7 Server quit message

Command: SQUIT
Parameters: <server> <comment>

The SQUIT message is needed to tell about quitting or dead servers.
If a server wishes to break the connection to another server it must
send a SQUIT message to the other server, using the the name of the
other server as the server parameter, which then closes its
connection to the quitting server.

This command is also available operators to help keep a network of
IRC servers connected in an orderly fashion. Operators may also
issue an SQUIT message for a remote server connection. In this case,
the SQUIT must be parsed by each server inbetween the operator and
the remote server, updating the view of the network held by each
server as explained below.

The <comment> should be supplied by all operators who execute a SQUIT
for a remote server (that is not connected to the server they are
currently on) so that other operators are aware for the reason of
this action. The <comment> is also filled in by servers which may
place an error or similar message here.

Both of the servers which are on either side of the connection being
closed are required to to send out a SQUIT message (to all its other
server connections) for all other servers which are considered to be
behind that link.

Similarly, a QUIT message must be sent to the other connected servers
rest of the network on behalf of all clients behind that link. In
addition to this, all channel members of a channel which lost a
member due to the split must be sent a QUIT message.

If a server connection is terminated prematurely (e.g. the server on
the other end of the link died), the server which detects
this disconnection is required to inform the rest of the network
that the connection has closed and fill in the comment field
with something appropriate.

Numeric replies:

ERR_NOPRIVILEGES ERR_NOSUCHSERVER

Example:

SQUIT tolsun.oulu.fi :Bad Link ? ; the server link tolson.oulu.fi has
been terminated because of "Bad Link".

:Trillian SQUIT cm22.eng.umd.edu :Server out of control
; message from Trillian to disconnect
"cm22.eng.umd.edu" from the net
because "Server out of control".

4.2 Channel operations

This group of messages is concerned with manipulating channels, their
properties (channel modes), and their contents (typically clients).
In implementing these, a number of race conditions are inevitable
when clients at opposing ends of a network send commands which will
ultimately clash. It is also required that servers keep a nickname
history to ensure that wherever a <nick> parameter is given, the
server check its history in case it has recently been changed.

4.2.1 Join message

Command: JOIN
Parameters: <channel>{,<channel>} [<key>{,<key>}]

The JOIN command is used by client to start listening a specific
channel. Whether or not a client is allowed to join a channel is
checked only by the server the client is connected to; all other
servers automatically add the user to the channel when it is received
from other servers. The conditions which affect this are as follows:

1. the user must be invited if the channel is invite-only;

2. the user's nick/username/hostname must not match any
active bans;

3. the correct key (password) must be given if it is set.

These are discussed in more detail under the MODE command (see
section 4.2.3 for more details).

Once a user has joined a channel, they receive notice about all
commands their server receives which affect the channel. This
includes MODE, KICK, PART, QUIT and of course PRIVMSG/NOTICE. The
JOIN command needs to be broadcast to all servers so that each server
knows where to find the users who are on the channel. This allows
optimal delivery of PRIVMSG/NOTICE messages to the channel.

If a JOIN is successful, the user is then sent the channel's topic
(using RPL_TOPIC) and the list of users who are on the channel (using
RPL_NAMREPLY), which must include the user joining.

Numeric Replies:

ERR_NEEDMOREPARAMS ERR_BANNEDFROMCHAN
ERR_INVITEONLYCHAN ERR_BADCHANNELKEY
ERR_CHANNELISFULL ERR_BADCHANMASK
ERR_NOSUCHCHANNEL ERR_TOOMANYCHANNELS
RPL_TOPIC

Examples:

JOIN #Foobar ; join channel #foobar.

JOIN &foo fubar ; join channel &foo using key "fubar".

JOIN #foo,&bar fubar ; join channel #foo using key "fubar"
and &bar using no key.

JOIN #foo,#bar fubar,foobar ; join channel #foo using key "fubar".
and channel #bar using key "foobar".

JOIN #foo,#bar ; join channels #foo and #bar.

:WiZ JOIN #Twilight_zone ; JOIN message from WiZ

4.2.2 Part message

Command: PART
Parameters: <channel>{,<channel>}

The PART message causes the client sending the message to be removed
from the list of active users for all given channels listed in the
parameter string.

Numeric Replies:

ERR_NEEDMOREPARAMS ERR_NOSUCHCHANNEL
ERR_NOTONCHANNEL

Examples:

PART #twilight_zone ; leave channel "#twilight_zone"

PART #oz-ops,&group5 ; leave both channels "&group5" and
"#oz-ops".

4.2.3 Mode message

Command: MODE

The MODE command is a dual-purpose command in IRC. It allows both
usernames and channels to have their mode changed. The rationale for
this choice is that one day nicknames will be obsolete and the
equivalent property will be the channel.

When parsing MODE messages, it is recommended that the entire message
be parsed first and then the changes which resulted then passed on.

4.2.3.1 Channel modes

Parameters: <channel> {[+-]opsitnbv} [<limit>] [<user>]
[<ban mask>]

The MODE command is provided so that channel operators may change the
characteristics of `their' channel. It is also required that servers
be able to change channel modes so that channel operators may be
created.

The various modes available for channels are as follows:

o - give/take channel operator privileges;
p - private channel flag;
s - secret channel flag;
i - invite-only channel flag;
t - topic settable by channel operator only flag;
n - no messages to channel from clients on the outside;
m - moderated channel;
l - set the user limit to channel;

b - set a ban mask to keep users out;
v - give/take the ability to speak on a moderated channel;
k - set a channel key (password).

When using the 'o' and 'b' options, a restriction on a total of three
per mode command has been imposed. That is, any combination of 'o'
and

4.2.3.2 User modes

Parameters: <nickname> {[+-]iwso}

The user MODEs are typically changes which affect either how the
client is seen by others or what 'extra' messages the client is sent.
A user MODE command may only be accepted if both the sender of the
message and the nickname given as a parameter are both the same.

The available modes are as follows:

i - marks a users as invisible;
s - marks a user for receipt of server notices;
w - user receives wallops;
o - operator flag.

Additional modes may be available later on.

If a user attempts to make themselves an operator using the "+o"
flag, the attempt should be ignored. There is no restriction,
however, on anyone `deopping' themselves (using "-o"). Numeric
Replies:

ERR_NEEDMOREPARAMS RPL_CHANNELMODEIS
ERR_CHANOPRIVSNEEDED ERR_NOSUCHNICK
ERR_NOTONCHANNEL ERR_KEYSET
RPL_BANLIST RPL_ENDOFBANLIST
ERR_UNKNOWNMODE ERR_NOSUCHCHANNEL

ERR_USERSDONTMATCH RPL_UMODEIS
ERR_UMODEUNKNOWNFLAG

Examples:

Use of Channel Modes:

MODE #Finnish +im ; Makes #Finnish channel moderated and
'invite-only'.

MODE #Finnish +o Kilroy ; Gives 'chanop' privileges to Kilroy on

channel #Finnish.

MODE #Finnish +v Wiz ; Allow WiZ to speak on #Finnish.

MODE #Fins -s ; Removes 'secret' flag from channel
#Fins.

MODE #42 +k oulu ; Set the channel key to "oulu".

MODE #eu-opers +l 10 ; Set the limit for the number of users
on channel to 10.

MODE &oulu +b ; list ban masks set for channel.

MODE &oulu +b *!*@* ; prevent all users from joining.

MODE &oulu +b *!*@*.edu ; prevent any user from a hostname
matching *.edu from joining.

Use of user Modes:

:MODE WiZ -w ; turns reception of WALLOPS messages
off for WiZ.

:Angel MODE Angel +i ; Message from Angel to make themselves
invisible.

MODE WiZ -o ; WiZ 'deopping' (removing operator
status). The plain reverse of this
command ("MODE WiZ +o") must not be
allowed from users since would bypass
the OPER command.

4.2.4 Topic message

Command: TOPIC
Parameters: <channel> [<topic>]

The TOPIC message is used to change or view the topic of a channel.
The topic for channel <channel> is returned if there is no <topic>
given. If the <topic> parameter is present, the topic for that
channel will be changed, if the channel modes permit this action.

Numeric Replies:

ERR_NEEDMOREPARAMS ERR_NOTONCHANNEL
RPL_NOTOPIC RPL_TOPIC
ERR_CHANOPRIVSNEEDED

Examples:

:Wiz TOPIC #test :New topic ;User Wiz setting the topic.

TOPIC #test :another topic ;set the topic on #test to "another
topic".

TOPIC #test ; check the topic for #test.

4.2.5 Names message

Command: NAMES
Parameters: [<channel>{,<channel>}]

By using the NAMES command, a user can list all nicknames that are
visible to them on any channel that they can see. Channel names
which they can see are those which aren't private (+p) or secret (+s)
or those which they are actually on. The <channel> parameter
specifies which channel(s) to return information about if valid.
There is no error reply for bad channel names.

If no <channel> parameter is given, a list of all channels and their
occupants is returned. At the end of this list, a list of users who
are visible but either not on any channel or not on a visible channel
are listed as being on `channel' "*".

Numerics:

RPL_NAMREPLY RPL_ENDOFNAMES

Examples:

NAMES #twilight_zone,#42 ; list visible users on #twilight_zone
and #42 if the channels are visible to
you.

NAMES ; list all visible channels and users

4.2.6 List message

Command: LIST
Parameters: [<channel>{,<channel>} [<server>]]

The list message is used to list channels and their topics. If the
<channel> parameter is used, only the status of that channel
is displayed. Private channels are listed (without their
topics) as channel "Prv" unless the client generating the query is
actually on that channel. Likewise, secret channels are not listed

at all unless the client is a member of the channel in question.

Numeric Replies:

ERR_NOSUCHSERVER RPL_LISTSTART
RPL_LIST RPL_LISTEND

Examples:

LIST ; List all channels.

LIST #twilight_zone,#42 ; List channels #twilight_zone and #42

4.2.7 Invite message

Command: INVITE
Parameters: <nickname> <channel>

The INVITE message is used to invite users to a channel. The
parameter <nickname> is the nickname of the person to be invited to
the target channel <channel>. There is no requirement that the
channel the target user is being invited to must exist or be a valid
channel. To invite a user to a channel which is invite only (MODE
+i), the client sending the invite must be recognised as being a
channel operator on the given channel.

Numeric Replies:

ERR_NEEDMOREPARAMS ERR_NOSUCHNICK
ERR_NOTONCHANNEL ERR_USERONCHANNEL
ERR_CHANOPRIVSNEEDED
RPL_INVITING RPL_AWAY

Examples:

:Angel INVITE Wiz #Dust ; User Angel inviting WiZ to channel
#Dust

INVITE Wiz #Twilight_Zone ; Command to invite WiZ to
#Twilight_zone

4.2.8 Kick command

Command: KICK
Parameters: <channel> <user> [<comment>]

The KICK command can be used to forcibly remove a user from a
channel. It 'kicks them out' of the channel (forced PART).

Only a channel operator may kick another user out of a channel.
Each server that receives a KICK message checks that it is valid
(ie the sender is actually a channel operator) before removing
the victim from the channel.

Numeric Replies:

ERR_NEEDMOREPARAMS ERR_NOSUCHCHANNEL
ERR_BADCHANMASK ERR_CHANOPRIVSNEEDED
ERR_NOTONCHANNEL

Examples:

KICK &Melbourne Matthew ; Kick Matthew from &Melbourne

KICK #Finnish John :Speaking English
; Kick John from #Finnish using
"Speaking English" as the reason
(comment).

:WiZ KICK #Finnish John ; KICK message from WiZ to remove John
from channel #Finnish

NOTE:
It is possible to extend the KICK command parameters to the
following:

<channel>{,<channel>} <user>{,<user>} [<comment>]

4.3 Server queries and commands

The server query group of commands has been designed to return
information about any server which is connected to the network. All
servers connected must respond to these queries and respond
correctly. Any invalid response (or lack thereof) must be considered
a sign of a broken server and it must be disconnected/disabled as
soon as possible until the situation is remedied.

In these queries, where a parameter appears as "<server>", it will
usually mean it can be a nickname or a server or a wildcard name of
some sort. For each parameter, however, only one query and set of
replies is to be generated.

4.3.1 Version message

Command: VERSION
Parameters: [<server>]

The VERSION message is used to query the version of the server
program. An optional parameter <server> is used to query the version
of the server program which a client is not directly connected to.

Numeric Replies:

ERR_NOSUCHSERVER RPL_VERSION

Examples:

:Wiz VERSION *.se ; message from Wiz to check the version
of a server matching "*.se"

VERSION tolsun.oulu.fi ; check the version of server
"tolsun.oulu.fi".

4.3.2 Stats message

Command: STATS
Parameters: [<query> [<server>]]

The stats message is used to query statistics of certain server. If
<server> parameter is omitted, only the end of stats reply is sent
back. The implementation of this command is highly dependent on the
server which replies, although the server must be able to supply
information as described by the queries below (or similar).

A query may be given by any single letter which is only checked by
the destination server (if given as the <server> parameter) and is
otherwise passed on by intermediate servers, ignored and unaltered.
The following queries are those found in the current IRC
implementation and provide a large portion of the setup information
for that server. Although these may not be supported in the same way
by other versions, all servers should be able to supply a valid reply
to a STATS query which is consistent with the reply formats currently
used and the purpose of the query.

The currently supported queries are:

c - returns a list of servers which the server may connect
to or allow connections from;
h - returns a list of servers which are either forced to be
treated as leaves or allowed to act as hubs;
i - returns a list of hosts which the server allows a client
to connect from;
k - returns a list of banned username/hostname combinations
for that server;
l - returns a list of the server's connections, showing how

long each connection has been established and the traffic
over that connection in bytes and messages for each
direction;
m - returns a list of commands supported by the server and
the usage count for each if the usage count is non zero;
o - returns a list of hosts from which normal clients may
become operators;
y - show Y (Class) lines from server's configuration file;
u - returns a string showing how long the server has been up.

Numeric Replies:

ERR_NOSUCHSERVER
RPL_STATSCLINE RPL_STATSNLINE
RPL_STATSILINE RPL_STATSKLINE
RPL_STATSQLINE RPL_STATSLLINE
RPL_STATSLINKINFO RPL_STATSUPTIME
RPL_STATSCOMMANDS RPL_STATSOLINE
RPL_STATSHLINE RPL_ENDOFSTATS

Examples:

STATS m ; check the command usage for the server
you are connected to

:Wiz STATS c eff.org ; request by WiZ for C/N line
information from server eff.org

4.3.3 Links message

Command: LINKS
Parameters: [[<remote server>] <server mask>]

With LINKS, a user can list all servers which are known by the server
answering the query. The returned list of servers must match the
mask, or if no mask is given, the full list is returned.

If <remote server> is given in addition to <server mask>, the LINKS
command is forwarded to the first server found that matches that name
(if any), and that server is then required to answer the query.

Numeric Replies:

ERR_NOSUCHSERVER
RPL_LINKS RPL_ENDOFLINKS

Examples:

LINKS *.au ; list all servers which have a name
that matches *.au;

:WiZ LINKS *.bu.edu *.edu ; LINKS message from WiZ to the first
server matching *.edu for a list of
servers matching *.bu.edu.

4.3.4 Time message

Command: TIME
Parameters: [<server>]

The time message is used to query local time from the specified
server. If the server parameter is not given, the server handling the
command must reply to the query.

Numeric Replies:

ERR_NOSUCHSERVER RPL_TIME

Examples:

TIME tolsun.oulu.fi ; check the time on the server
"tolson.oulu.fi"

Angel TIME *.au ; user angel checking the time on a
server matching "*.au"

4.3.5 Connect message

Command: CONNECT
Parameters: <target server> [<port> [<remote server>]]

The CONNECT command can be used to force a server to try to establish
a new connection to another server immediately. CONNECT is a
privileged command and is to be available only to IRC Operators. If
a remote server is given then the CONNECT attempt is made by that
server to <target server> and <port>.

Numeric Replies:

ERR_NOSUCHSERVER ERR_NOPRIVILEGES
ERR_NEEDMOREPARAMS

Examples:

CONNECT tolsun.oulu.fi ; Attempt to connect a server to
tolsun.oulu.fi

:WiZ CONNECT eff.org 6667 csd.bu.edu
; CONNECT attempt by WiZ to get servers
eff.org and csd.bu.edu connected on port
6667.

4.3.6 Trace message

Command: TRACE
Parameters: [<server>]

TRACE command is used to find the route to specific server. Each
server that processes this message must tell the sender about it by
sending a reply indicating it is a pass-through link, forming a chain
of replies similar to that gained from using "traceroute". After
sending this reply back, it must then send the TRACE message to the
next server until given server is reached. If the <server> parameter
is omitted, it is recommended that TRACE command send a message to
the sender telling which servers the current server has direct
connection to.

If the destination given by "<server>" is an actual server, then the
destination server is required to report all servers and users which
are connected to it, although only operators are permitted to see
users present. If the destination given by <server> is a nickname,
they only a reply for that nickname is given.

Numeric Replies:

ERR_NOSUCHSERVER

If the TRACE message is destined for another server, all intermediate
servers must return a RPL_TRACELINK reply to indicate that the TRACE
passed through it and where its going next.

RPL_TRACELINK
A TRACE reply may be composed of any number of the following numeric
replies.

RPL_TRACECONNECTING RPL_TRACEHANDSHAKE
RPL_TRACEUNKNOWN RPL_TRACEOPERATOR
RPL_TRACEUSER RPL_TRACESERVER
RPL_TRACESERVICE RPL_TRACENEWTYPE
RPL_TRACECLASS

Examples:

TRACE *.oulu.fi ; TRACE to a server matching *.oulu.fi

:WiZ TRACE AngelDust ; TRACE issued by WiZ to nick AngelDust

4.3.7 Admin command

Command: ADMIN
Parameters: [<server>]

The admin message is used to find the name of the administrator of
the given server, or current server if <server> parameter is omitted.
Each server must have the ability to forward ADMIN messages to other
servers.

Numeric Replies:

ERR_NOSUCHSERVER
RPL_ADMINME RPL_ADMINLOC1
RPL_ADMINLOC2 RPL_ADMINEMAIL

Examples:

ADMIN tolsun.oulu.fi ; request an ADMIN reply from
tolsun.oulu.fi

:WiZ ADMIN *.edu ; ADMIN request from WiZ for first
server found to match *.edu.

4.3.8 Info command

Command: INFO
Parameters: [<server>]

The INFO command is required to return information which describes
the server: its version, when it was compiled, the patchlevel, when
it was started, and any other miscellaneous information which may be
considered to be relevant.

Numeric Replies:

ERR_NOSUCHSERVER
RPL_INFO RPL_ENDOFINFO

Examples:

INFO csd.bu.edu ; request an INFO reply from
csd.bu.edu

:Avalon INFO *.fi ; INFO request from Avalon for first
server found to match *.fi.

INFO Angel ; request info from the server that
Angel is connected to.

4.4 Sending messages

The main purpose of the IRC protocol is to provide a base for clients
to communicate with each other. PRIVMSG and NOTICE are the only
messages available which actually perform delivery of a text message
from one client to another - the rest just make it possible and try
to ensure it happens in a reliable and structured manner.

4.4.1 Private messages

Command: PRIVMSG
Parameters: <receiver>{,<receiver>} <text to be sent>

PRIVMSG is used to send private messages between users. <receiver>
is the nickname of the receiver of the message. <receiver> can also
be a list of names or channels separated with commas.

The <receiver> parameter may also me a host mask (#mask) or server
mask ($mask). In both cases the server will only send the PRIVMSG
to those who have a server or host matching the mask. The mask must
have at least 1 (one) "." in it and no wildcards following the
last ".". This requirement exists to prevent people sending messages
to "#*" or "$*", which would broadcast to all users; from
experience, this is abused more than used responsibly and properly.
Wildcards are the '*' and '?' characters. This extension to
the PRIVMSG command is only available to Operators.

Numeric Replies:

ERR_NORECIPIENT ERR_NOTEXTTOSEND
ERR_CANNOTSENDTOCHAN ERR_NOTOPLEVEL
ERR_WILDTOPLEVEL ERR_TOOMANYTARGETS
ERR_NOSUCHNICK
RPL_AWAY

Examples:

:Angel PRIVMSG Wiz :Hello are you receiving this message ?
; Message from Angel to Wiz.

PRIVMSG Angel :yes I'm receiving it !receiving it !'u>(768u+1n) .br ;
Message to Angel.

PRIVMSG [email protected] :Hello !
; Message to a client on server

tolsun.oulu.fi with username of "jto".

PRIVMSG $*.fi :Server tolsun.oulu.fi rebooting.
; Message to everyone on a server which
has a name matching *.fi.

PRIVMSG #*.edu :NSFNet is undergoing work, expect interruptions
; Message to all users who come from a
host which has a name matching *.edu.

4.4.2 Notice

Command: NOTICE
Parameters: <nickname> <text>

The NOTICE message is used similarly to PRIVMSG. The difference
between NOTICE and PRIVMSG is that automatic replies must never be
sent in response to a NOTICE message. This rule applies to servers
too - they must not send any error reply back to the client on
receipt of a notice. The object of this rule is to avoid loops
between a client automatically sending something in response to
something it received. This is typically used by automatons (clients
with either an AI or other interactive program controlling their
actions) which are always seen to be replying lest they end up in a
loop with another automaton.

See PRIVMSG for more details on replies and examples.

4.5 User based queries

User queries are a group of commands which are primarily concerned
with finding details on a particular user or group users. When using
wildcards with any of these commands, if they match, they will only
return information on users who are 'visible' to you. The visibility
of a user is determined as a combination of the user's mode and the
common set of channels you are both on.

4.5.1 Who query

Command: WHO
Parameters: [<name> [<o>]]

The WHO message is used by a client to generate a query which returns
a list of information which 'matches' the <name> parameter given by
the client. In the absence of the <name> parameter, all visible
(users who aren't invisible (user mode +i) and who don't have a
common channel with the requesting client) are listed. The same
result can be achieved by using a <name> of "0" or any wildcard which

will end up matching every entry possible.

The <name> passed to WHO is matched against users' host, server, real
name and nickname if the channel <name> cannot be found.

If the "o" parameter is passed only operators are returned according
to the name mask supplied.

Numeric Replies:

ERR_NOSUCHSERVER
RPL_WHOREPLY RPL_ENDOFWHO

Examples:

WHO *.fi ; List all users who match against
"*.fi".

WHO jto* o ; List all users with a match against<br