• The server sends Replies 001 to 004 to a user upon

successful registration.

RPL_BOUNCE=005 # "Try server <server name>, port <port number>"

• Sent by the server to a user to suggest an alternative

server. This is often used when the connection is refused because the server is already full.

• Reply format used by USERHOST to list replies to

the query list. The reply string is composed as follows:

reply = nickname [ "*" ] "=" ( "+" / "-" ) 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.

• Reply format used by ISON to list replies to the

query list.

• 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.

• 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.

• 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 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).

• Replies RPL_LIST, RPL_LISTEND mark the 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 end reply MUST be sent.

• 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.

• Returned by the server to indicate that the

attempted INVITE message was successful and is being passed onto the end client.

• Returned by a server answering a SUMMON message to

indicate that it is summoning that user.

• When listing the ‘invitations masks’ for a given channel,

a server is required to send the list back using the RPL_INVITELIST and RPL_ENDOFINVITELIST messages. A separate RPL_INVITELIST is sent for each active mask. After the masks have been listed (or if none present) a RPL_ENDOFINVITELIST MUST be sent.

• When listing the ‘exception masks’ for a given channel,

a server is required to send the list back using the RPL_EXCEPTLIST and RPL_ENDOFEXCEPTLIST messages. A separate RPL_EXCEPTLIST is sent for each active mask. After the masks have been listed (or if none present) a RPL_ENDOFEXCEPTLIST MUST be sent.

• Reply by the server showing its version details.

The <version> is the version of the software being 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.

• 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.

• "@" is used for secret channels, "*" for private

channels, and "=" for others (public channels).

• 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.

• 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.

• 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 banmask. After the banmasks have been listed (or if none present) a RPL_ENDOFBANLIST MUST be sent.

• 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.

• 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 MUST be surrounded by a RPL_MOTDSTART (before the RPL_MOTDs) and an RPL_ENDOFMOTD (after).

• RPL_YOUREOPER is sent back to a client which has

just successfully issued an OPER message and gained operator status.

• If the REHASH option is used and an operator sends

a REHASH message, an RPL_REHASHING is sent back to the operator.

• Sent by the server to a service upon successful

registration.

• 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.

• 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.

• The RPL_TRACE* are all returned by the server in

response to the TRACE message. How many are returned is dependent on the TRACE message and 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. RPL_TRACEEND is sent to indicate the end of the list.

• reports statistics on a connection. <linkname>

identifies the particular connection, <sendq> is the amount of data that is queued and waiting to be sent <sent messages> the number of messages sent, and <sent Kbytes> the amount of data sent, in Kbytes. <received messages> and <received Kbytes> are the equivalent of <sent messages> and <sent Kbytes> for received data, respectively. <time open> indicates how long ago the connection was opened, in seconds.

• reports statistics on commands usage.

• reports the server uptime.

• reports the allowed hosts from where user may become IRC

operators.

• To answer a query about a client’s own mode,

RPL_UMODEIS is sent back.

• When listing services in reply to a SERVLIST message,

a server is required to send the list back using the RPL_SERVLIST and RPL_SERVLISTEND messages. A separate RPL_SERVLIST is sent for each service. After the services have been listed (or if none present) a RPL_SERVLISTEND MUST be sent.

• 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.

• When replying to an ADMIN message, a server

is expected to use replies RPL_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 institution (RPL_ADMINLOC2) and finally the administrative contact for the server (an email address here is REQUIRED) in RPL_ADMINEMAIL.

• When a server drops a command without processing it,

it MUST use the reply RPL_TRYAGAIN to inform the originating client.

5.2 Error Replies

Error replies are found in the range from 400 to 599.

• Used to indicate the nickname parameter supplied to a

command is currently unused.

• Used to indicate the server name given currently

does not exist.

• Used to indicate the given channel name is invalid.

• 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 or where the user is banned and is trying to send a PRIVMSG message to that channel.

• Sent to a user when they have joined the maximum

number of allowed channels and they try to join another channel.

• Returned by WHOWAS to indicate there is no history

information for that nickname.

• 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.

• Returned to a client which trying to send a

PRIVMSG/NOTICE to too many recipients.

• Returned to a client which is attempting to JOIN a safe

channel using the shortname when there are more than one such channel.

• Returned to a client which is attempting to send a SQUERY

to a service which does not exist.

• PING or PONG message missing the originator parameter.

• 412 - 415 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.

• Returned to a registered client to indicate that the

command sent is unknown by the server.

• Server’s MOTD file could not be opened by the server.

• Returned by a server in response to an ADMIN message

when there is an error in finding the appropriate information.

• Generic error message used to report a failed file

operation during the processing of a message.

• Returned when a nickname parameter expected for a

command and isn’t found.

• Returned after receiving a NICK message which contains

characters which do not fall in the defined set. See section 2.3.1 for details on valid nicknames.

• Returned when a NICK message is processed that results

in an attempt to change to a currently existing nickname.

• Returned by a server to a client when it detects a

nickname collision (registered of a NICK that already exists by another server).

• Returned by a server to a user trying to join a channel

currently blocked by the channel delay mechanism.

• Returned by a server to a user trying to change nickname

when the desired nickname is blocked by the nick delay mechanism.

• Returned by the server to indicate that the target

user of the command is not on the given channel.

• Returned by the server whenever a client tries to

perform a channel affecting command for which the client isn’t a member.

• Returned when a client tries to invite a user to a

channel they are already on.

• Returned by the summon after a SUMMON command for a

user was unable to be performed since they were not logged in.

• Returned as a response to the SUMMON command. MUST be

returned by any server which doesn’t implement it.

• Returned as a response to the USERS command. MUST be

returned by any server which does not implement it.

• Returned by the server to indicate that the client

MUST be registered before the server will allow it to be parsed in detail.

• Returned by the server by numerous commands to

indicate to the client that it didn’t supply enough parameters.

• 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).

• 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.

• Returned to indicate a failed attempt at registering

a connection for which a password was required and was either not given or incorrect.

• Returned after an attempt to connect and register

yourself with a server which has been setup to explicitly deny connections to you.

• Sent by a server to a user to inform that access to the

• Any command requiring operator privileges to operate

MUST return this error to indicate the attempt was unsuccessful.

• 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.

• Any attempts to use the KILL command on a server

are to be refused and this error returned directly to the client.

• Sent by the server to a user upon connection to indicate

the restricted nature of the connection (user mode "+r").

• Any MODE requiring "channel creator" privileges MUST

return this error if the client making the attempt is not a chanop on the specified channel.

• 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.

• 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.

• Error sent to any user trying to view or change the

user mode for a user other than themselves.

5.3 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.