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
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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
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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
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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 ]
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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
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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
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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
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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
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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> ::= '-' | '[' | ']' | '\'
| '`' | '^' | '{' | '}'
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<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.
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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.
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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
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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:
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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.
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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
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; 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:
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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
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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.
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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;
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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>}
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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;
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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
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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
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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
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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).
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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>]
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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
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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:
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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
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: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
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: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.
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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
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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
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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
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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.
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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.
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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
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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]
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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.
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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>]
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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.
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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.
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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"
- Used to indicate the nickname parameter supplied to a
command is currently unused.
402
ERR_NOSUCHSERVER
"<server name> :No such server"
- Used to indicate the server name given currently
doesn't exist.
403
ERR_NOSUCHCHANNEL
"<channel name> :No such channel"
- Used to indicate the given channel name is invalid.
404
ERR_CANNOTSENDTOCHAN
"<channel name> :Cannot send to channel"
- 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"
- Returned by WHOWAS to indicate there is no history
information for that nickname.
407
ERR_TOOMANYTARGETS
"<target> :Duplicate recipients. No message \
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delivered"
- 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"
- 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"
- 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"
- Returned to a registered client to indicate that the
command sent is unknown by the server.
422
ERR_NOMOTD
":MOTD File is missing"
- Server's MOTD file could not be opened by the server.
423
ERR_NOADMININFO
"<server> :No administrative info available"
- 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>"
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- Generic error message used to report a failed file
operation during the processing of a message.
431
ERR_NONICKNAMEGIVEN
":No nickname given"
- Returned when a nickname parameter expected for a
command and isn't found.
432
ERR_ERRONEUSNICKNAME
"<nick> :Erroneus nickname"
- 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"
- 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"
- 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"
- 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"
- 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"
- Returned when a client tries to invite a user to a
channel they are already on.
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444
ERR_NOLOGIN
"<user> :User not logged in"
- 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"
- 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"
- 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"
- 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"
- 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"
- 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"
- 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.
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464
ERR_PASSWDMISMATCH
":Password incorrect"
- 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"
- 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"
- 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"
- 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!"
- Any attempts to use the KILL command on a server
are to be refused and this error returned directly
to the client.
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491
ERR_NOOPERHOST
":No O-lines for your host"
- 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"
- 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"
- 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>}]"
- 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>}]"
- Reply format used by ISON to list replies to the
query list.
301
RPL_AWAY
"<nick> :<away message>"
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305
RPL_UNAWAY
":You are no longer marked as being away"
306
RPL_NOWAWAY
":You have been marked as being away"
- 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>}"
- 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"
- 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
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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"
- 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>"
- 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>"
- 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"
- Returned by a server answering a SUMMON message to
indicate that it is summoning that user.
351
RPL_VERSION
"<version>.<debuglevel> <server> :<comments>"
- Reply by the server showing its version details.
The <version> is the version of the software being
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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"
- 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"
- 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"
- 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
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"<channel> :End of channel ban list"
- 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"
- 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"
- 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"
- 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"
- 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
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"<server> :<string showing server's local time>"
- 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"
- 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>"
- 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
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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>"
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- 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"
- 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>"
- 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.
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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
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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
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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
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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).
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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
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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
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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.
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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
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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
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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
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