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rfc:rfc1459

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

Oikarinen & Reed [Page 1] RFC 1459 Internet Relay Chat Protocol May 1993

       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

Oikarinen & Reed [Page 2] RFC 1459 Internet Relay Chat Protocol May 1993

    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

Oikarinen & Reed [Page 3] RFC 1459 Internet Relay Chat Protocol May 1993

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 ]

Oikarinen & Reed [Page 4] RFC 1459 Internet Relay Chat Protocol May 1993

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

Oikarinen & Reed [Page 5] RFC 1459 Internet Relay Chat Protocol May 1993

 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

Oikarinen & Reed [Page 6] RFC 1459 Internet Relay Chat Protocol May 1993

 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

Oikarinen & Reed [Page 7] RFC 1459 Internet Relay Chat Protocol May 1993

 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

Oikarinen & Reed [Page 8] RFC 1459 Internet Relay Chat Protocol May 1993

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 RFC 952 [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>    ::= '-' | '[' | ']' | '\' | '`' | '^' | '{' | '}'

Oikarinen & Reed [Page 9] RFC 1459 Internet Relay Chat Protocol May 1993

 <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.

Oikarinen & Reed [Page 10] RFC 1459 Internet Relay Chat Protocol May 1993

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.

Oikarinen & Reed [Page 11] RFC 1459 Internet Relay Chat Protocol May 1993

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

Oikarinen & Reed [Page 12] RFC 1459 Internet Relay Chat Protocol May 1993

 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:

Oikarinen & Reed [Page 13] RFC 1459 Internet Relay Chat Protocol May 1993

         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.

Oikarinen & Reed [Page 14] RFC 1459 Internet Relay Chat Protocol May 1993

 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

Oikarinen & Reed [Page 15] RFC 1459 Internet Relay Chat Protocol May 1993

                                 ; 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:

Oikarinen & Reed [Page 16] RFC 1459 Internet Relay Chat Protocol May 1993

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

Oikarinen & Reed [Page 17] RFC 1459 Internet Relay Chat Protocol May 1993

 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.

Oikarinen & Reed [Page 18] RFC 1459 Internet Relay Chat Protocol May 1993

 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;

Oikarinen & Reed [Page 19] RFC 1459 Internet Relay Chat Protocol May 1993

         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>}

Oikarinen & Reed [Page 20] RFC 1459 Internet Relay Chat Protocol May 1993

 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> {[+|-]|o|p|s|i|t|n|b|v} [<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;

Oikarinen & Reed [Page 21] RFC 1459 Internet Relay Chat Protocol May 1993

         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> {[+|-]|i|w|s|o}
 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

Oikarinen & Reed [Page 22] RFC 1459 Internet Relay Chat Protocol May 1993

                              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

Oikarinen & Reed [Page 23] RFC 1459 Internet Relay Chat Protocol May 1993

 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

Oikarinen & Reed [Page 24] RFC 1459 Internet Relay Chat Protocol May 1993

 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).

Oikarinen & Reed [Page 25] RFC 1459 Internet Relay Chat Protocol May 1993

 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>]

Oikarinen & Reed [Page 26] RFC 1459 Internet Relay Chat Protocol May 1993

 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

Oikarinen & Reed [Page 27] RFC 1459 Internet Relay Chat Protocol May 1993

             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:

Oikarinen & Reed [Page 28] RFC 1459 Internet Relay Chat Protocol May 1993

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

Oikarinen & Reed [Page 29] RFC 1459 Internet Relay Chat Protocol May 1993

: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

Oikarinen & Reed [Page 30] RFC 1459 Internet Relay Chat Protocol May 1993

: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.

Oikarinen & Reed [Page 31] RFC 1459 Internet Relay Chat Protocol May 1993

 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 jto@tolsun.oulu.fi :Hello !

                              ; Message to a client on server

Oikarinen & Reed [Page 32] RFC 1459 Internet Relay Chat Protocol May 1993

                              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

Oikarinen & Reed [Page 33] RFC 1459 Internet Relay Chat Protocol May 1993

 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
                                 "jto*" if they are an operator.

4.5.2 Whois query

    Command: WHOIS
 Parameters: [<server>] <nickmask>[,<nickmask>[,...]]
 This message is used to query information about particular user.  The
 server will answer this message with several numeric messages
 indicating different statuses of each user which matches the nickmask
 (if you are entitled to see them).  If no wildcard is present in the
 <nickmask>, any information about that nick which you are allowed to
 see is presented.  A comma (',') separated list of nicknames may be
 given.
 The latter version sends the query to a specific server.  It is
 useful if you want to know how long the user in question has been
 idle as only local server (ie. the server the user is directly
 connected to) knows that information, while everything else is
 globally known.
 Numeric Replies:
         ERR_NOSUCHSERVER                ERR_NONICKNAMEGIVEN
         RPL_WHOISUSER                   RPL_WHOISCHANNELS
         RPL_WHOISCHANNELS               RPL_WHOISSERVER
         RPL_AWAY                        RPL_WHOISOPERATOR
         RPL_WHOISIDLE                   ERR_NOSUCHNICK
         RPL_ENDOFWHOIS

Oikarinen & Reed [Page 34] RFC 1459 Internet Relay Chat Protocol May 1993

 Examples:
 WHOIS wiz                       ; return available user information
                                 about nick WiZ
 WHOIS eff.org trillian          ; ask server eff.org for user
                                 information about trillian

4.5.3 Whowas

    Command: WHOWAS
 Parameters: <nickname> [<count> [<server>]]
 Whowas asks for information about a nickname which no longer exists.
 This may either be due to a nickname change or the user leaving IRC.
 In response to this query, the server searches through its nickname
 history, looking for any nicks which are lexically the same (no wild
 card matching here).  The history is searched backward, returning the
 most recent entry first.  If there are multiple entries, up to
 <count> replies will be returned (or all of them if no <count>
 parameter is given).  If a non-positive number is passed as being
 <count>, then a full search is done.
 Numeric Replies:
         ERR_NONICKNAMEGIVEN             ERR_WASNOSUCHNICK
         RPL_WHOWASUSER                  RPL_WHOISSERVER
         RPL_ENDOFWHOWAS
 Examples:
 WHOWAS Wiz                      ; return all information in the nick
                                 history about nick "WiZ";
 WHOWAS Mermaid 9                ; return at most, the 9 most recent
                                 entries in the nick history for
                                 "Mermaid";
 WHOWAS Trillian 1 *.edu         ; return the most recent history for
                                 "Trillian" from the first server found
                                 to match "*.edu".

4.6 Miscellaneous messages

 Messages in this category do not fit into any of the above categories
 but are nonetheless still a part of and required by the protocol.

Oikarinen & Reed [Page 35] RFC 1459 Internet Relay Chat Protocol May 1993

4.6.1 Kill message

    Command: KILL
 Parameters: <nickname> <comment>
 The KILL message is used to cause a client-server connection to be
 closed by the server which has the actual connection.  KILL is used
 by servers when they encounter a duplicate entry in the list of valid
 nicknames and is used to remove both entries.  It is also available
 to operators.
 Clients which have automatic reconnect algorithms effectively make
 this command useless since the disconnection is only brief.  It does
 however break the flow of data and can be used to stop large amounts
 of being abused, any user may elect to receive KILL messages
 generated for others to keep an 'eye' on would be trouble spots.
 In an arena where nicknames are required to be globally unique at all
 times, KILL messages are sent whenever 'duplicates' are detected
 (that is an attempt to register two users with the same nickname) in
 the hope that both of them will disappear and only 1 reappear.
 The comment given must reflect the actual reason for the KILL.  For
 server-generated KILLs it usually is made up of details concerning
 the origins of the two conflicting nicknames.  For users it is left
 up to them to provide an adequate reason to satisfy others who see
 it.  To prevent/discourage fake KILLs from being generated to hide
 the identify of the KILLer, the comment also shows a 'kill-path'
 which is updated by each server it passes through, each prepending
 its name to the path.
 Numeric Replies:
         ERR_NOPRIVILEGES                ERR_NEEDMOREPARAMS
         ERR_NOSUCHNICK                  ERR_CANTKILLSERVER
 KILL David (csd.bu.edu <- tolsun.oulu.fi)
                                 ; Nickname collision between csd.bu.edu
                                 and tolson.oulu.fi
 NOTE:
 It is recommended that only Operators be allowed to kill other users
 with KILL message.  In an ideal world not even operators would need
 to do this and it would be left to servers to deal with.

Oikarinen & Reed [Page 36] RFC 1459 Internet Relay Chat Protocol May 1993

4.6.2 Ping message

    Command: PING
 Parameters: <server1> [<server2>]
 The PING message is used to test the presence of an active client at
 the other end of the connection.  A PING message is sent at regular
 intervals if no other activity detected coming from a connection.  If
 a connection fails to respond to a PING command within a set amount
 of time, that connection is closed.
 Any client which receives a PING message must respond to <server1>
 (server which sent the PING message out) as quickly as possible with
 an appropriate PONG message to indicate it is still there and alive.
 Servers should not respond to PING commands but rely on PINGs from
 the other end of the connection to indicate the connection is alive.
 If the <server2> parameter is specified, the PING message gets
 forwarded there.
 Numeric Replies:
         ERR_NOORIGIN                    ERR_NOSUCHSERVER
 Examples:
 PING tolsun.oulu.fi             ; server sending a PING message to
                                 another server to indicate it is still
                                 alive.
 PING WiZ                        ; PING message being sent to nick WiZ

4.6.3 Pong message

    Command: PONG
 Parameters: <daemon> [<daemon2>]
 PONG message is a reply to ping message.  If parameter <daemon2> is
 given this message must be forwarded to given daemon.  The <daemon>
 parameter is the name of the daemon who has responded to PING message
 and generated this message.
 Numeric Replies:
         ERR_NOORIGIN                    ERR_NOSUCHSERVER
 Examples:
 PONG csd.bu.edu tolsun.oulu.fi  ; PONG message from csd.bu.edu to

Oikarinen & Reed [Page 37] RFC 1459 Internet Relay Chat Protocol May 1993

                                 tolsun.oulu.fi

4.6.4 Error

    Command: ERROR
 Parameters: <error message>
 The ERROR command is for use by servers when reporting a serious or
 fatal error to its operators.  It may also be sent from one server to
 another but must not be accepted from any normal unknown clients.
 An ERROR message is for use for reporting errors which occur with a
 server-to-server link only.  An ERROR message is sent to the server
 at the other end (which sends it to all of its connected operators)
 and to all operators currently connected.  It is not to be passed
 onto any other servers by a server if it is received from a server.
 When a server sends a received ERROR message to its operators, the
 message should be encapsulated inside a NOTICE message, indicating
 that the client was not responsible for the error.
 Numerics:
         None.
 Examples:
 ERROR :Server *.fi already exists; ERROR message to the other server
                                 which caused this error.
 NOTICE WiZ :ERROR from csd.bu.edu -- Server *.fi already exists
                                 ; Same ERROR message as above but sent
                                 to user WiZ on the other server.

5. OPTIONALS

 This section describes OPTIONAL messages.  They are not required in a
 working server implementation of the protocol described herein.  In
 the absence of the option, an error reply message must be generated
 or an unknown command error.  If the message is destined for another
 server to answer then it must be passed on (elementary parsing
 required) The allocated numerics for this are listed with the
 messages below.

5.1 Away

    Command: AWAY
 Parameters: [message]

Oikarinen & Reed [Page 38] RFC 1459 Internet Relay Chat Protocol May 1993

 With the AWAY message, clients can set an automatic reply string for
 any PRIVMSG commands directed at them (not to a channel they are on).
 The automatic reply is sent by the server to client sending the
 PRIVMSG command.  The only replying server is the one to which the
 sending client is connected to.
 The AWAY message is used either with one parameter (to set an AWAY
 message) or with no parameters (to remove the AWAY message).
 Numeric Replies:
         RPL_UNAWAY                      RPL_NOWAWAY
 Examples:
 AWAY :Gone to lunch.  Back in 5 ; set away message to "Gone to lunch.
                                 Back in 5".
 :WiZ AWAY                       ; unmark WiZ as being away.

5.2 Rehash message

    Command: REHASH
 Parameters: None
 The rehash message can be used by the operator to force the server to
 re-read and process its configuration file.
 Numeric Replies:
      RPL_REHASHING                   ERR_NOPRIVILEGES

Examples:

REHASH ; message from client with operator

                              status to server asking it to reread its
                              configuration file.

5.3 Restart message

    Command: RESTART
 Parameters: None
 The restart message can only be used by an operator to force a server
 restart itself.  This message is optional since it may be viewed as a
 risk to allow arbitrary people to connect to a server as an operator
 and execute this command, causing (at least) a disruption to service.

Oikarinen & Reed [Page 39] RFC 1459 Internet Relay Chat Protocol May 1993

 The RESTART command must always be fully processed by the server to
 which the sending client is connected and not be passed onto other
 connected servers.
 Numeric Replies:
         ERR_NOPRIVILEGES
 Examples:
 RESTART                         ; no parameters required.

5.4 Summon message

    Command: SUMMON
 Parameters: <user> [<server>]
 The SUMMON command can be used to give users who are on a host
 running an IRC server a message asking them to please join IRC.  This
 message is only sent if the target server (a) has SUMMON enabled, (b)
 the user is logged in and (c) the server process can write to the
 user's tty (or similar).
 If no <server> parameter is given it tries to summon <user> from the
 server the client is connected to is assumed as the target.
 If summon is not enabled in a server, it must return the
 ERR_SUMMONDISABLED numeric and pass the summon message onwards.
 Numeric Replies:
         ERR_NORECIPIENT                 ERR_FILEERROR
         ERR_NOLOGIN                     ERR_NOSUCHSERVER
         RPL_SUMMONING
 Examples:
 SUMMON jto                      ; summon user jto on the server's host
 SUMMON jto tolsun.oulu.fi       ; summon user jto on the host which a
                                 server named "tolsun.oulu.fi" is
                                 running.

5.5 Users

    Command: USERS
 Parameters: [<server>]

Oikarinen & Reed [Page 40] RFC 1459 Internet Relay Chat Protocol May 1993

 The USERS command returns a list of users logged into the server in a
 similar  format  to  who(1),  rusers(1)  and finger(1).  Some people
 may disable this command on their server for security related
 reasons.   If disabled, the correct numeric must be returned to
 indicate this.
 Numeric Replies:
         ERR_NOSUCHSERVER                ERR_FILEERROR
         RPL_USERSSTART                  RPL_USERS
         RPL_NOUSERS                     RPL_ENDOFUSERS
         ERR_USERSDISABLED
 Disabled Reply:
         ERR_USERSDISABLED
 Examples:

USERS eff.org ; request a list of users logged in on

                              server eff.org

:John USERS tolsun.oulu.fi ; request from John for a list of users

                              logged in on server tolsun.oulu.fi

5.6 Operwall message

    Command: WALLOPS
 Parameters: Text to be sent to all operators currently online
 Sends  a  message  to  all   operators   currently   online.    After
 implementing  WALLOPS  as  a user command it was found that it was
 often and commonly abused as a means of sending a message to a lot
 of  people (much  similar to WALL).  Due to this it is recommended
 that the current implementation of  WALLOPS  be  used  as  an
 example  by  allowing  and recognising only servers as the senders of
 WALLOPS.
 Numeric Replies:
         ERR_NEEDMOREPARAMS
 Examples:
 :csd.bu.edu WALLOPS :Connect '*.uiuc.edu 6667' from Joshua; WALLOPS
                                 message from csd.bu.edu announcing a
                                 CONNECT message it received and acted
                                 upon from Joshua.

Oikarinen & Reed [Page 41] RFC 1459 Internet Relay Chat Protocol May 1993

5.7 Userhost message

    Command: USERHOST
 Parameters: <nickname>{<space><nickname>}
 The USERHOST command takes a list of up to 5 nicknames, each
 separated by a space character and returns a list of information
 about each nickname that it found.  The returned list has each reply
 separated by a space.
 Numeric Replies:
         RPL_USERHOST                    ERR_NEEDMOREPARAMS
 Examples:
 USERHOST Wiz Michael Marty p    ;USERHOST request for information on
                                 nicks "Wiz", "Michael", "Marty" and "p"

5.8 Ison message

    Command: ISON
 Parameters: <nickname>{<space><nickname>}
 The ISON command was implemented to provide  a  quick  and  efficient
 means  to get a response about whether a given nickname was currently
 on IRC. ISON only takes one (1) parameter: a space-separated list of
 nicks.  For  each  nickname in the list that is present, the server
 adds that to its reply string.  Thus the reply string may return
 empty (none  of  the given  nicks are present), an exact copy of the
 parameter string (all of them present) or as any other subset of the
 set of nicks  given  in  the parameter.  The only limit on the number
 of nicks that may be checked is that the combined length must not be
 too large as to cause the server to chop it off so it fits in 512
 characters.
 ISON is only be processed by the server local to the client sending
 the command and thus not passed onto other servers for further
 processing.
 Numeric Replies:
         RPL_ISON                ERR_NEEDMOREPARAMS
 Examples:
 ISON phone trillian WiZ jarlek Avalon Angel Monstah
                                 ; Sample ISON request for 7 nicks.

Oikarinen & Reed [Page 42] RFC 1459 Internet Relay Chat Protocol May 1993

6. REPLIES

 The following is a list of numeric replies which are generated in
 response to the commands given above.  Each numeric is given with its
 number, name and reply string.

6.1 Error Replies.

      401     ERR_NOSUCHNICK
                      "<nickname> :No such nick/channel"
  1. Used to indicate the nickname parameter supplied to a

command is currently unused.

      402     ERR_NOSUCHSERVER
                      "<server name> :No such server"
  1. Used to indicate the server name given currently

doesn't exist.

      403     ERR_NOSUCHCHANNEL
                      "<channel name> :No such channel"
  1. Used to indicate the given channel name is invalid.
      404     ERR_CANNOTSENDTOCHAN
                      "<channel name> :Cannot send to channel"
  1. Sent to a user who is either (a) not on a channel

which is mode +n or (b) not a chanop (or mode +v) on

                a channel which has mode +m set and is trying to send
                a PRIVMSG message to that channel.
      405     ERR_TOOMANYCHANNELS
                      "<channel name> :You have joined too many \
                       channels"
              - Sent to a user when they have joined the maximum
                number of allowed channels and they try to join
                another channel.
      406     ERR_WASNOSUCHNICK
                      "<nickname> :There was no such nickname"
  1. Returned by WHOWAS to indicate there is no history

information for that nickname.

      407     ERR_TOOMANYTARGETS
                      "<target> :Duplicate recipients. No message \

Oikarinen & Reed [Page 43] RFC 1459 Internet Relay Chat Protocol May 1993

                       delivered"
  1. Returned to a client which is attempting to send a

PRIVMSG/NOTICE using the user@host destination format

                and for a user@host which has several occurrences.
      409     ERR_NOORIGIN
                      ":No origin specified"
  1. PING or PONG message missing the originator parameter

which is required since these commands must work

                without valid prefixes.
      411     ERR_NORECIPIENT
                      ":No recipient given (<command>)"
      412     ERR_NOTEXTTOSEND
                      ":No text to send"
      413     ERR_NOTOPLEVEL
                      "<mask> :No toplevel domain specified"
      414     ERR_WILDTOPLEVEL
                      "<mask> :Wildcard in toplevel domain"
  1. 412 - 414 are returned by PRIVMSG to indicate that

the message wasn't delivered for some reason.

                ERR_NOTOPLEVEL and ERR_WILDTOPLEVEL are errors that
                are returned when an invalid use of
                "PRIVMSG $<server>" or "PRIVMSG #<host>" is attempted.
      421     ERR_UNKNOWNCOMMAND
                      "<command> :Unknown command"
  1. Returned to a registered client to indicate that the

command sent is unknown by the server.

      422     ERR_NOMOTD
                      ":MOTD File is missing"
  1. Server's MOTD file could not be opened by the server.
      423     ERR_NOADMININFO
                      "<server> :No administrative info available"
  1. Returned by a server in response to an ADMIN message

when there is an error in finding the appropriate

                information.
      424     ERR_FILEERROR
              ":File error doing <file op> on <file>"

Oikarinen & Reed [Page 44] RFC 1459 Internet Relay Chat Protocol May 1993

  1. Generic error message used to report a failed file

operation during the processing of a message.

      431     ERR_NONICKNAMEGIVEN
                      ":No nickname given"
  1. Returned when a nickname parameter expected for a

command and isn't found.

      432     ERR_ERRONEUSNICKNAME
                      "<nick> :Erroneus nickname"
  1. Returned after receiving a NICK message which contains

characters which do not fall in the defined set. See

                section x.x.x for details on valid nicknames.
      433     ERR_NICKNAMEINUSE
                      "<nick> :Nickname is already in use"
  1. Returned when a NICK message is processed that results

in an attempt to change to a currently existing

                nickname.
      436     ERR_NICKCOLLISION
                      "<nick> :Nickname collision KILL"
  1. Returned by a server to a client when it detects a

nickname collision (registered of a NICK that

                already exists by another server).
      441     ERR_USERNOTINCHANNEL
                      "<nick> <channel> :They aren't on that channel"
  1. Returned by the server to indicate that the target

user of the command is not on the given channel.

      442     ERR_NOTONCHANNEL
                      "<channel> :You're not on that channel"
  1. Returned by the server whenever a client tries to

perform a channel effecting command for which the

                client isn't a member.
      443     ERR_USERONCHANNEL
                      "<user> <channel> :is already on channel"
  1. Returned when a client tries to invite a user to a

channel they are already on.

Oikarinen & Reed [Page 45] RFC 1459 Internet Relay Chat Protocol May 1993

      444     ERR_NOLOGIN
                      "<user> :User not logged in"
  1. Returned by the summon after a SUMMON command for a

user was unable to be performed since they were not

                logged in.
      445     ERR_SUMMONDISABLED
                      ":SUMMON has been disabled"
  1. Returned as a response to the SUMMON command. Must be

returned by any server which does not implement it.

      446     ERR_USERSDISABLED
                      ":USERS has been disabled"
  1. Returned as a response to the USERS command. Must be

returned by any server which does not implement it.

      451     ERR_NOTREGISTERED
                      ":You have not registered"
  1. Returned by the server to indicate that the client

must be registered before the server will allow it

                to be parsed in detail.
      461     ERR_NEEDMOREPARAMS
                      "<command> :Not enough parameters"
  1. Returned by the server by numerous commands to

indicate to the client that it didn't supply enough

                parameters.
      462     ERR_ALREADYREGISTRED
                      ":You may not reregister"
  1. Returned by the server to any link which tries to

change part of the registered details (such as

                password or user details from second USER message).
      463     ERR_NOPERMFORHOST
                      ":Your host isn't among the privileged"
  1. Returned to a client which attempts to register with

a server which does not been setup to allow

                connections from the host the attempted connection
                is tried.

Oikarinen & Reed [Page 46] RFC 1459 Internet Relay Chat Protocol May 1993

      464     ERR_PASSWDMISMATCH
                      ":Password incorrect"
  1. Returned to indicate a failed attempt at registering

a connection for which a password was required and

                was either not given or incorrect.
      465     ERR_YOUREBANNEDCREEP
                      ":You are banned from this server"
  1. Returned after an attempt to connect and register

yourself with a server which has been setup to

                explicitly deny connections to you.
      467     ERR_KEYSET
                      "<channel> :Channel key already set"
      471     ERR_CHANNELISFULL
                      "<channel> :Cannot join channel (+l)"
      472     ERR_UNKNOWNMODE
                      "<char> :is unknown mode char to me"
      473     ERR_INVITEONLYCHAN
                      "<channel> :Cannot join channel (+i)"
      474     ERR_BANNEDFROMCHAN
                      "<channel> :Cannot join channel (+b)"
      475     ERR_BADCHANNELKEY
                      "<channel> :Cannot join channel (+k)"
      481     ERR_NOPRIVILEGES
                      ":Permission Denied- You're not an IRC operator"
  1. Any command requiring operator privileges to operate

must return this error to indicate the attempt was

                unsuccessful.
      482     ERR_CHANOPRIVSNEEDED
                      "<channel> :You're not channel operator"
  1. Any command requiring 'chanop' privileges (such as

MODE messages) must return this error if the client

                making the attempt is not a chanop on the specified
                channel.
      483     ERR_CANTKILLSERVER
                      ":You cant kill a server!"
  1. Any attempts to use the KILL command on a server

are to be refused and this error returned directly

                to the client.

Oikarinen & Reed [Page 47] RFC 1459 Internet Relay Chat Protocol May 1993

      491     ERR_NOOPERHOST
                      ":No O-lines for your host"
  1. If a client sends an OPER message and the server has

not been configured to allow connections from the

                client's host as an operator, this error must be
                returned.
      501     ERR_UMODEUNKNOWNFLAG
                      ":Unknown MODE flag"
  1. Returned by the server to indicate that a MODE

message was sent with a nickname parameter and that

                the a mode flag sent was not recognized.
      502     ERR_USERSDONTMATCH
                      ":Cant change mode for other users"
  1. Error sent to any user trying to view or change the

user mode for a user other than themselves.

6.2 Command responses.

      300     RPL_NONE
                      Dummy reply number. Not used.
      302     RPL_USERHOST
                      ":[<reply>{<space><reply>}]"
  1. Reply format used by USERHOST to list replies to

the query list. The reply string is composed as

                follows:
                <reply> ::= <nick>['*'] '=' <'+'|'-'><hostname>
                The '*' indicates whether the client has registered
                as an Operator.  The '-' or '+' characters represent
                whether the client has set an AWAY message or not
                respectively.
      303     RPL_ISON
                      ":[<nick> {<space><nick>}]"
  1. Reply format used by ISON to list replies to the

query list.

      301     RPL_AWAY
                      "<nick> :<away message>"

Oikarinen & Reed [Page 48] RFC 1459 Internet Relay Chat Protocol May 1993

      305     RPL_UNAWAY
                      ":You are no longer marked as being away"
      306     RPL_NOWAWAY
                      ":You have been marked as being away"
  1. These replies are used with the AWAY command (if

allowed). RPL_AWAY is sent to any client sending a

                PRIVMSG to a client which is away.  RPL_AWAY is only
                sent by the server to which the client is connected.
                Replies RPL_UNAWAY and RPL_NOWAWAY are sent when the
                client removes and sets an AWAY message.
      311     RPL_WHOISUSER
                      "<nick> <user> <host> * :<real name>"
      312     RPL_WHOISSERVER
                      "<nick> <server> :<server info>"
      313     RPL_WHOISOPERATOR
                      "<nick> :is an IRC operator"
      317     RPL_WHOISIDLE
                      "<nick> <integer> :seconds idle"
      318     RPL_ENDOFWHOIS
                      "<nick> :End of /WHOIS list"
      319     RPL_WHOISCHANNELS
                      "<nick> :{[@|+]<channel><space>}"
  1. Replies 311 - 313, 317 - 319 are all replies

generated in response to a WHOIS message. Given that

                there are enough parameters present, the answering
                server must either formulate a reply out of the above
                numerics (if the query nick is found) or return an
                error reply.  The '*' in RPL_WHOISUSER is there as
                the literal character and not as a wild card.  For
                each reply set, only RPL_WHOISCHANNELS may appear
                more than once (for long lists of channel names).
                The '@' and '+' characters next to the channel name
                indicate whether a client is a channel operator or
                has been granted permission to speak on a moderated
                channel.  The RPL_ENDOFWHOIS reply is used to mark
                the end of processing a WHOIS message.
      314     RPL_WHOWASUSER
                      "<nick> <user> <host> * :<real name>"
      369     RPL_ENDOFWHOWAS
                      "<nick> :End of WHOWAS"
  1. When replying to a WHOWAS message, a server must use

the replies RPL_WHOWASUSER, RPL_WHOISSERVER or

                ERR_WASNOSUCHNICK for each nickname in the presented

Oikarinen & Reed [Page 49] RFC 1459 Internet Relay Chat Protocol May 1993

                list.  At the end of all reply batches, there must
                be RPL_ENDOFWHOWAS (even if there was only one reply
                and it was an error).
      321     RPL_LISTSTART
                      "Channel :Users  Name"
      322     RPL_LIST
                      "<channel> <# visible> :<topic>"
      323     RPL_LISTEND
                      ":End of /LIST"
  1. Replies RPL_LISTSTART, RPL_LIST, RPL_LISTEND mark

the start, actual replies with data and end of the

                server's response to a LIST command.  If there are
                no channels available to return, only the start
                and end reply must be sent.
      324     RPL_CHANNELMODEIS
                      "<channel> <mode> <mode params>"
      331     RPL_NOTOPIC
                      "<channel> :No topic is set"
      332     RPL_TOPIC
                      "<channel> :<topic>"
  1. When sending a TOPIC message to determine the

channel topic, one of two replies is sent. If

                the topic is set, RPL_TOPIC is sent back else
                RPL_NOTOPIC.
      341     RPL_INVITING
                      "<channel> <nick>"
  1. Returned by the server to indicate that the

attempted INVITE message was successful and is

                being passed onto the end client.
      342     RPL_SUMMONING
                      "<user> :Summoning user to IRC"
  1. Returned by a server answering a SUMMON message to

indicate that it is summoning that user.

      351     RPL_VERSION
                      "<version>.<debuglevel> <server> :<comments>"
  1. Reply by the server showing its version details.

The <version> is the version of the software being

Oikarinen & Reed [Page 50] RFC 1459 Internet Relay Chat Protocol May 1993

                used (including any patchlevel revisions) and the
                <debuglevel> is used to indicate if the server is
                running in "debug mode".
                The "comments" field may contain any comments about
                the version or further version details.
      352     RPL_WHOREPLY
                      "<channel> <user> <host> <server> <nick> \
                       <H|G>[*][@|+] :<hopcount> <real name>"
      315     RPL_ENDOFWHO
                      "<name> :End of /WHO list"
  1. The RPL_WHOREPLY and RPL_ENDOFWHO pair are used

to answer a WHO message. The RPL_WHOREPLY is only

                sent if there is an appropriate match to the WHO
                query.  If there is a list of parameters supplied
                with a WHO message, a RPL_ENDOFWHO must be sent
                after processing each list item with <name> being
                the item.
      353     RPL_NAMREPLY
                      "<channel> :[[@|+]<nick> [[@|+]<nick> [...]]]"
      366     RPL_ENDOFNAMES
                      "<channel> :End of /NAMES list"
  1. To reply to a NAMES message, a reply pair consisting

of RPL_NAMREPLY and RPL_ENDOFNAMES is sent by the

                server back to the client.  If there is no channel
                found as in the query, then only RPL_ENDOFNAMES is
                returned.  The exception to this is when a NAMES
                message is sent with no parameters and all visible
                channels and contents are sent back in a series of
                RPL_NAMEREPLY messages with a RPL_ENDOFNAMES to mark
                the end.
      364     RPL_LINKS
                      "<mask> <server> :<hopcount> <server info>"
      365     RPL_ENDOFLINKS
                      "<mask> :End of /LINKS list"
  1. In replying to the LINKS message, a server must send

replies back using the RPL_LINKS numeric and mark the

                end of the list using an RPL_ENDOFLINKS reply.
      367     RPL_BANLIST
                      "<channel> <banid>"
      368     RPL_ENDOFBANLIST

Oikarinen & Reed [Page 51] RFC 1459 Internet Relay Chat Protocol May 1993

                      "<channel> :End of channel ban list"
  1. When listing the active 'bans' for a given channel,

a server is required to send the list back using the

                RPL_BANLIST and RPL_ENDOFBANLIST messages.  A separate
                RPL_BANLIST is sent for each active banid.  After the
                banids have been listed (or if none present) a
                RPL_ENDOFBANLIST must be sent.
      371     RPL_INFO
                      ":<string>"
      374     RPL_ENDOFINFO
                      ":End of /INFO list"
  1. A server responding to an INFO message is required to

send all its 'info' in a series of RPL_INFO messages

                with a RPL_ENDOFINFO reply to indicate the end of the
                replies.
      375     RPL_MOTDSTART
                      ":- <server> Message of the day - "
      372     RPL_MOTD
                      ":- <text>"
      376     RPL_ENDOFMOTD
                      ":End of /MOTD command"
  1. When responding to the MOTD message and the MOTD file

is found, the file is displayed line by line, with

                each line no longer than 80 characters, using
                RPL_MOTD format replies.  These should be surrounded
                by a RPL_MOTDSTART (before the RPL_MOTDs) and an
                RPL_ENDOFMOTD (after).
      381     RPL_YOUREOPER
                      ":You are now an IRC operator"
  1. RPL_YOUREOPER is sent back to a client which has

just successfully issued an OPER message and gained

                operator status.
      382     RPL_REHASHING
                      "<config file> :Rehashing"
  1. If the REHASH option is used and an operator sends

a REHASH message, an RPL_REHASHING is sent back to

                the operator.
      391     RPL_TIME

Oikarinen & Reed [Page 52] RFC 1459 Internet Relay Chat Protocol May 1993

                      "<server> :<string showing server's local time>"
  1. When replying to the TIME message, a server must send

the reply using the RPL_TIME format above. The string

                showing the time need only contain the correct day and
                time there.  There is no further requirement for the
                time string.
      392     RPL_USERSSTART
                      ":UserID   Terminal  Host"
      393     RPL_USERS
                      ":%-8s %-9s %-8s"
      394     RPL_ENDOFUSERS
                      ":End of users"
      395     RPL_NOUSERS
                      ":Nobody logged in"
  1. If the USERS message is handled by a server, the

replies RPL_USERSTART, RPL_USERS, RPL_ENDOFUSERS and

                RPL_NOUSERS are used.  RPL_USERSSTART must be sent
                first, following by either a sequence of RPL_USERS
                or a single RPL_NOUSER.  Following this is
                RPL_ENDOFUSERS.
      200     RPL_TRACELINK
                      "Link <version & debug level> <destination> \
                       <next server>"
      201     RPL_TRACECONNECTING
                      "Try. <class> <server>"
      202     RPL_TRACEHANDSHAKE
                      "H.S. <class> <server>"
      203     RPL_TRACEUNKNOWN
                      "???? <class> [<client IP address in dot form>]"
      204     RPL_TRACEOPERATOR
                      "Oper <class> <nick>"
      205     RPL_TRACEUSER
                      "User <class> <nick>"
      206     RPL_TRACESERVER
                      "Serv <class> <int>S <int>C <server> \
                       <nick!user|*!*>@<host|server>"
      208     RPL_TRACENEWTYPE
                      "<newtype> 0 <client name>"
      261     RPL_TRACELOG
                      "File <logfile> <debug level>"
  1. The RPL_TRACE* are all returned by the server in

response to the TRACE message. How many are

                returned is dependent on the the TRACE message and

Oikarinen & Reed [Page 53] RFC 1459 Internet Relay Chat Protocol May 1993

                whether it was sent by an operator or not.  There
                is no predefined order for which occurs first.
                Replies RPL_TRACEUNKNOWN, RPL_TRACECONNECTING and
                RPL_TRACEHANDSHAKE are all used for connections
                which have not been fully established and are either
                unknown, still attempting to connect or in the
                process of completing the 'server handshake'.
                RPL_TRACELINK is sent by any server which handles
                a TRACE message and has to pass it on to another
                server.  The list of RPL_TRACELINKs sent in
                response to a TRACE command traversing the IRC
                network should reflect the actual connectivity of
                the servers themselves along that path.
                RPL_TRACENEWTYPE is to be used for any connection
                which does not fit in the other categories but is
                being displayed anyway.
      211     RPL_STATSLINKINFO
                      "<linkname> <sendq> <sent messages> \
                       <sent bytes> <received messages> \
                       <received bytes> <time open>"
      212     RPL_STATSCOMMANDS
                      "<command> <count>"
      213     RPL_STATSCLINE
                      "C <host> * <name> <port> <class>"
      214     RPL_STATSNLINE
                      "N <host> * <name> <port> <class>"
      215     RPL_STATSILINE
                      "I <host> * <host> <port> <class>"
      216     RPL_STATSKLINE
                      "K <host> * <username> <port> <class>"
      218     RPL_STATSYLINE
                      "Y <class> <ping frequency> <connect \
                       frequency> <max sendq>"
      219     RPL_ENDOFSTATS
                      "<stats letter> :End of /STATS report"
      241     RPL_STATSLLINE
                      "L <hostmask> * <servername> <maxdepth>"
      242     RPL_STATSUPTIME
                      ":Server Up %d days %d:%02d:%02d"
      243     RPL_STATSOLINE
                      "O <hostmask> * <name>"
      244     RPL_STATSHLINE
                      "H <hostmask> * <servername>"
      221     RPL_UMODEIS
                      "<user mode string>"

Oikarinen & Reed [Page 54] RFC 1459 Internet Relay Chat Protocol May 1993

  1. To answer a query about a client's own mode,

RPL_UMODEIS is sent back.

      251     RPL_LUSERCLIENT
                      ":There are <integer> users and <integer> \
                       invisible on <integer> servers"
      252     RPL_LUSEROP
                      "<integer> :operator(s) online"
      253     RPL_LUSERUNKNOWN
                      "<integer> :unknown connection(s)"
      254     RPL_LUSERCHANNELS
                      "<integer> :channels formed"
      255     RPL_LUSERME
                      ":I have <integer> clients and <integer> \
                        servers"
  1. In processing an LUSERS message, the server

sends a set of replies from RPL_LUSERCLIENT,

                        RPL_LUSEROP, RPL_USERUNKNOWN,
                        RPL_LUSERCHANNELS and RPL_LUSERME.  When
                        replying, a server must send back
                        RPL_LUSERCLIENT and RPL_LUSERME.  The other
                        replies are only sent back if a non-zero count
                        is found for them.
      256     RPL_ADMINME
                      "<server> :Administrative info"
      257     RPL_ADMINLOC1
                      ":<admin info>"
      258     RPL_ADMINLOC2
                      ":<admin info>"
      259     RPL_ADMINEMAIL
                      ":<admin info>"
  1. When replying to an ADMIN message, a server

is expected to use replies RLP_ADMINME

                        through to RPL_ADMINEMAIL and provide a text
                        message with each.  For RPL_ADMINLOC1 a
                        description of what city, state and country
                        the server is in is expected, followed by
                        details of the university and department
                        (RPL_ADMINLOC2) and finally the administrative
                        contact for the server (an email address here
                        is required) in RPL_ADMINEMAIL.

Oikarinen & Reed [Page 55] RFC 1459 Internet Relay Chat Protocol May 1993

6.3 Reserved numerics.

 These numerics are not described above since they fall into one of
 the following categories:
      1. no longer in use;
      2. reserved for future planned use;
      3. in current use but are part of a non-generic 'feature' of
         the current IRC server.
      209     RPL_TRACECLASS          217     RPL_STATSQLINE
      231     RPL_SERVICEINFO         232     RPL_ENDOFSERVICES
      233     RPL_SERVICE             234     RPL_SERVLIST
      235     RPL_SERVLISTEND
      316     RPL_WHOISCHANOP         361     RPL_KILLDONE
      362     RPL_CLOSING             363     RPL_CLOSEEND
      373     RPL_INFOSTART           384     RPL_MYPORTIS
      466     ERR_YOUWILLBEBANNED     476     ERR_BADCHANMASK
      492     ERR_NOSERVICEHOST

7. Client and server authentication

 Clients and servers are both subject to the same level of
 authentication.  For both, an IP number to hostname lookup (and
 reverse check on this) is performed for all connections made to the
 server.  Both connections are then subject to a password check (if
 there is a password set for that connection).  These checks are
 possible on all connections although the password check is only
 commonly used with servers.
 An additional check that is becoming of more and more common is that
 of the username responsible for making the connection.  Finding the
 username of the other end of the connection typically involves
 connecting to an authentication server such as IDENT as described in
 RFC 1413.
 Given that without passwords it is not easy to reliably determine who
 is on the other end of a network connection, use of passwords is
 strongly recommended on inter-server connections in addition to any
 other measures such as using an ident server.

8. Current implementations

 The only current implementation of this protocol is the IRC server,
 version 2.8. Earlier versions may implement some or all of the
 commands described by this document with NOTICE messages replacing

Oikarinen & Reed [Page 56] RFC 1459 Internet Relay Chat Protocol May 1993

 many of the numeric replies.  Unfortunately, due to backward
 compatibility requirements, the implementation of some parts of this
 document varies with what is laid out.  On notable difference is:
  • recognition that any LF or CR anywhere in a message marks the

end of that message (instead of requiring CR-LF);

 The rest of this section deals with issues that are mostly of
 importance to those who wish to implement a server but some parts
 also apply directly to clients as well.

8.1 Network protocol: TCP - why it is best used here.

 IRC has been implemented on top of TCP since TCP supplies a reliable
 network protocol which is well suited to this scale of conferencing.
 The use of multicast IP is an alternative, but it is not widely
 available or supported at the present time.

8.1.1 Support of Unix sockets

 Given that Unix domain sockets allow listen/connect operations, the
 current implementation can be configured to listen and accept both
 client and server connections on a Unix domain socket.  These are
 recognized as sockets where the hostname starts with a '/'.
 When providing any information about the connections on a Unix domain
 socket, the server is required to supplant the actual hostname in
 place of the pathname unless the actual socket name is being asked
 for.

8.2 Command Parsing

 To provide useful 'non-buffered' network IO for clients and servers,
 each connection is given its own private 'input buffer' in which the
 results of the most recent read and parsing are kept.  A buffer size
 of 512 bytes is used so as to hold 1 full message, although, this
 will usually hold several commands.  The private buffer is parsed
 after every read operation for valid messages.  When dealing with
 multiple messages from one client in the buffer, care should be taken
 in case one happens to cause the client to be 'removed'.

8.3 Message delivery

 It is common to find network links saturated or hosts to which you
 are sending data unable to send data.  Although Unix typically
 handles this through the TCP window and internal buffers, the server
 often has large amounts of data to send (especially when a new
 server-server link forms) and the small buffers provided in the

Oikarinen & Reed [Page 57] RFC 1459 Internet Relay Chat Protocol May 1993

 kernel are not enough for the outgoing queue.  To alleviate this
 problem, a "send queue" is used as a FIFO queue for data to be sent.
 A typical "send queue" may grow to 200 Kbytes on a large IRC network
 with a slow network connection when a new server connects.
 When polling its connections, a server will first read and parse all
 incoming data, queuing any data to be sent out. When all available
 input is processed, the queued data is sent. This reduces the number
 of write() system calls and helps TCP make bigger packets.

8.4 Connection 'Liveness'

 To detect when a connection has died or become unresponsive, the
 server must ping each of its connections that it doesn't get a
 response from in a given amount of time.
 If a connection doesn't respond in time, its connection is closed
 using the appropriate procedures.  A connection is also dropped if
 its sendq grows beyond the maximum allowed, because it is better to
 close a slow connection than have a server process block.

8.5 Establishing a server to client connection

 Upon connecting to an IRC server, a client is sent the MOTD (if
 present) as well as the current user/server count (as per the LUSER
 command).  The server is also required to give an unambiguous message
 to the client which states its name and version as well as any other
 introductory messages which may be deemed appropriate.
 After dealing with this, the server must then send out the new user's
 nickname and other information as supplied by itself (USER command)
 and as the server could discover (from DNS/authentication servers).
 The server must send this information out with NICK first followed by
 USER.

8.6 Establishing a server-server connection.

 The process of establishing of a server-to-server connection is
 fraught with danger since there are many possible areas where
 problems can occur - the least of which are race conditions.
 After a server has received a connection following by a PASS/SERVER
 pair which were recognised as being valid, the server should then
 reply with its own PASS/SERVER information for that connection as
 well as all of the other state information it knows about as
 described below.
 When the initiating server receives a PASS/SERVER pair, it too then

Oikarinen & Reed [Page 58] RFC 1459 Internet Relay Chat Protocol May 1993

 checks that the server responding is authenticated properly before
 accepting the connection to be that server.

8.6.1 Server exchange of state information when connecting

 The order of state information being exchanged between servers is
 essential.  The required order is as follows:
  • all known other servers;
  • all known user information;
  • all known channel information.
 Information regarding servers is sent via extra SERVER messages, user
 information with NICK/USER/MODE/JOIN messages and channels with MODE
 messages.
 NOTE: channel topics are *NOT* exchanged here because the TOPIC
 command overwrites any old topic information, so at best, the two
 sides of the connection would exchange topics.
 By passing the state information about servers first, any collisions
 with servers that already exist occur before nickname collisions due
 to a second server introducing a particular nickname.  Due to the IRC
 network only being able to exist as an acyclic graph, it may be
 possible that the network has already reconnected in another
 location, the place where the collision occurs indicating where the
 net needs to split.

8.7 Terminating server-client connections

 When a client connection closes, a QUIT message is generated on
 behalf of the client by the server to which the client connected.  No
 other message is to be generated or used.

8.8 Terminating server-server connections

 If a server-server connection is closed, either via a remotely
 generated SQUIT or 'natural' causes, the rest of the connected IRC
 network must have its information updated with by the server which
 detected the closure.  The server then sends a list of SQUITs (one
 for each server behind that connection) and a list of QUITs (again,
 one for each client behind that connection).

Oikarinen & Reed [Page 59] RFC 1459 Internet Relay Chat Protocol May 1993

8.9 Tracking nickname changes

 All IRC servers are required to keep a history of recent nickname
 changes.  This is required to allow the server to have a chance of
 keeping in touch of things when nick-change race conditions occur
 with commands which manipulate them.  Commands which must trace nick
 changes are:
  • KILL (the nick being killed)
  • MODE (+/- o,v)
  • KICK (the nick being kicked)
 No other commands are to have nick changes checked for.
 In the above cases, the server is required to first check for the
 existence of the nickname, then check its history to see who that
 nick currently belongs to (if anyone!).  This reduces the chances of
 race conditions but they can still occur with the server ending up
 affecting the wrong client.  When performing a change trace for an
 above command it is recommended that a time range be given and
 entries which are too old ignored.
 For a reasonable history, a server should be able to keep previous
 nickname for every client it knows about if they all decided to
 change.  This size is limited by other factors (such as memory, etc).

8.10 Flood control of clients

 With a large network of interconnected IRC servers, it is quite easy
 for any single client attached to the network to supply a continuous
 stream of messages that result in not only flooding the network, but
 also degrading the level of service provided to others.  Rather than
 require every 'victim' to be provide their own protection, flood
 protection was written into the server and is applied to all clients
 except services.  The current algorithm is as follows:
  • check to see if client's `message timer' is less than

current time (set to be equal if it is);

  • read any data present from the client;
  • while the timer is less than ten seconds ahead of the current

time, parse any present messages and penalize the client by

        2 seconds for each message;
 which in essence means that the client may send 1 message every 2

Oikarinen & Reed [Page 60] RFC 1459 Internet Relay Chat Protocol May 1993

 seconds without being adversely affected.

8.11 Non-blocking lookups

 In a real-time environment, it is essential that a server process do
 as little waiting as possible so that all the clients are serviced
 fairly.  Obviously this requires non-blocking IO on all network
 read/write operations.  For normal server connections, this was not
 difficult, but there are other support operations that may cause the
 server to block (such as disk reads).  Where possible, such activity
 should be performed with a short timeout.

8.11.1 Hostname (DNS) lookups

 Using the standard resolver libraries from Berkeley and others has
 meant large delays in some cases where replies have timed out.  To
 avoid this, a separate set of DNS routines were written which were
 setup for non-blocking IO operations and then polled from within the
 main server IO loop.

8.11.2 Username (Ident) lookups

 Although there are numerous ident libraries for use and inclusion
 into other programs, these caused problems since they operated in a
 synchronous manner and resulted in frequent delays.  Again the
 solution was to write a set of routines which would cooperate with
 the rest of the server and work using non-blocking IO.

8.12 Configuration File

 To provide a flexible way of setting up and running the server, it is
 recommended that a configuration file be used which contains
 instructions to the server on the following:
  • which hosts to accept client connections from;
  • which hosts to allow to connect as servers;
  • which hosts to connect to (both actively and

passively);

  • information about where the server is (university,

city/state, company are examples of this);

  • who is responsible for the server and an email address

at which they can be contacted;

  • hostnames and passwords for clients which wish to be given

Oikarinen & Reed [Page 61] RFC 1459 Internet Relay Chat Protocol May 1993

        access to restricted operator commands.
 In specifying hostnames, both domain names and use of the 'dot'
 notation (127.0.0.1) should both be accepted.  It must be possible to
 specify the password to be used/accepted for all outgoing and
 incoming connections (although the only outgoing connections are
 those to other servers).
 The above list is the minimum requirement for any server which wishes
 to make a connection with another server.  Other items which may be
 of use are:
  • specifying which servers other server may introduce;
  • how deep a server branch is allowed to become;
  • hours during which clients may connect.

8.12.1 Allowing clients to connect

 A server should use some sort of 'access control list' (either in the
 configuration file or elsewhere) that is read at startup and used to
 decide what hosts clients may use to connect to it.
 Both 'deny' and 'allow' should be implemented to provide the required
 flexibility for host access control.

8.12.2 Operators

 The granting of operator privileges to a disruptive person can have
 dire consequences for the well-being of the IRC net in general due to
 the powers given to them.  Thus, the acquisition of such powers
 should not be very easy.  The current setup requires two 'passwords'
 to be used although one of them is usually easy guessed.  Storage of
 oper passwords in configuration files is preferable to hard coding
 them in and should be stored in a crypted format (ie using crypt(3)
 from Unix) to prevent easy theft.

8.12.3 Allowing servers to connect

 The interconnection of server is not a trivial matter: a bad
 connection can have a large impact on the usefulness of IRC.  Thus,
 each server should have a list of servers to which it may connect and
 which servers may connect to it.  Under no circumstances should a
 server allow an arbitrary host to connect as a server.  In addition
 to which servers may and may not connect, the configuration file
 should also store the password and other characteristics of that
 link.

Oikarinen & Reed [Page 62] RFC 1459 Internet Relay Chat Protocol May 1993

8.12.4 Administrivia

 To provide accurate and valid replies to the ADMIN command (see
 section 4.3.7), the server should find the relevant details in the
 configuration.

8.13 Channel membership

 The current server allows any registered local user to join upto 10
 different channels.  There is no limit imposed on non-local users so
 that the server remains (reasonably) consistant with all others on a
 channel membership basis

9. Current problems

 There are a number of recognized problems with this protocol, all  of
 which  hope to be solved sometime in the near future during its
 rewrite.  Currently, work is underway to find working solutions to
 these problems.

9.1 Scalability

 It is widely recognized that this protocol does not scale
 sufficiently well when used in a large arena.  The main problem comes
 from the requirement that all servers know about all other servers
 and users and that information regarding them be updated as soon as
 it changes.  It is also desirable to keep the number of servers low
 so that the path length between any two points is kept minimal and
 the spanning tree as strongly branched as possible.

9.2 Labels

 The current IRC protocol has 3 types of labels: the nickname, the
 channel name and the server name.  Each of the three types has its
 own domain and no duplicates are allowed inside that domain.
 Currently, it is possible for users to pick the label for any of the
 three, resulting in collisions.  It is widely recognized that this
 needs reworking, with a plan for unique names for channels and nicks
 that don't collide being desirable as well as a solution allowing a
 cyclic tree.

9.2.1 Nicknames

 The idea of the nickname on IRC is very convenient for users to use
 when talking to each other outside of a channel, but there is only a
 finite nickname space and being what they are, its not uncommon for
 several people to want to use the same nick.  If a nickname is chosen
 by two people using this protocol, either one will not succeed or

Oikarinen & Reed [Page 63] RFC 1459 Internet Relay Chat Protocol May 1993

 both will removed by use of KILL (4.6.1).

9.2.2 Channels

 The current channel layout requires that all servers know about all
 channels, their inhabitants and properties.  Besides not scaling
 well, the issue of privacy is also a concern.  A collision of
 channels is treated as an inclusive event (both people who create the
 new channel are considered to be members of it) rather than an
 exclusive one such as used to solve nickname collisions.

9.2.3 Servers

 Although the number of servers is usually small relative to the
 number of users and channels, they two currently required to be known
 globally, either each one separately or hidden behind a mask.

9.3 Algorithms

 In some places within the server code, it has not  been  possible  to
 avoid  N^2  algorithms  such  as  checking  the channel list of a set
 of clients.
 In current server versions, there are no database consistency checks,
 each server assumes that a neighbouring server is correct.  This
 opens the door to large problems if a connecting server is buggy or
 otherwise tries to introduce contradictions to the existing net.
 Currently, because of the lack of unique internal and global labels,
 there are a multitude of race conditions that exist.  These race
 conditions generally arise from the problem of it taking time for
 messages to traverse and effect the IRC network.  Even by changing to
 unique labels, there are problems with channel-related commands being
 disrupted.

10. Current support and availability

         Mailing lists for IRC related discussion:
              Future protocol: ircd-three-request@eff.org
              General discussion: operlist-request@eff.org
         Software implemenations
              cs.bu.edu:/irc
              nic.funet.fi:/pub/irc
              coombs.anu.edu.au:/pub/irc
         Newsgroup: alt.irc

Oikarinen & Reed [Page 64] RFC 1459 Internet Relay Chat Protocol May 1993

Security Considerations

 Security issues are discussed in sections 4.1, 4.1.1, 4.1.3, 5.5, and
 7.

12. Authors' Addresses

 Jarkko Oikarinen
 Tuirantie 17 as 9
 90500 OULU
 FINLAND
 Email: jto@tolsun.oulu.fi
 Darren Reed
 4 Pateman Street
 Watsonia, Victoria 3087
 Australia
 Email: avalon@coombs.anu.edu.au

Oikarinen & Reed [Page 65]

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