ft_irc - Internet Relay Chat Server

An IRC server implementation in C++98, compliant with RFC 1459/2812 protocols.

Table of Contents

• Overview
• Features
• Requirements
• Compilation
• Usage
• Project Structure
• IRC Commands
• Channel Modes
• Numeric Reply Codes
• Classes
• Technical Details

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Overview

ft_irc is a lightweight IRC server that allows multiple clients to connect, authenticate, join channels, and communicate with each other. The server uses non-blocking I/O with poll() to handle multiple connections simultaneously without threading.

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Features

• Multi-client support using poll() for non-blocking I/O
• Password-protected server access
• Channel creation and management
• Channel operator privileges
• Private messaging between users
• Channel modes (invite-only, topic restriction, password, user limit)
• RFC 1459/2812 compliant message format
• Compatible with standard IRC clients (irssi, HexChat, WeeChat, etc.)

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Requirements

• C++98 compatible compiler (g++, clang++)
• POSIX-compliant system (Linux, macOS)
• Make

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Compilation

make        # Build the server
make clean  # Remove object files
make fclean # Remove object files and executable
make re     # Rebuild from scratch

Compilation flags: -Wall -Wextra -Werror -std=c++98

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Usage

./ircserv <port> <password>

Parameters:

• port - The port number for incoming connections (1-65535)
• password - The server password required for client authentication

Example:

./ircserv 6667 mysecretpassword

Connecting with a client:

# Using netcat (for testing)
nc localhost 6667

# Using irssi
irssi -c localhost -p 6667 -w mysecretpassword

# Using HexChat
# Server: localhost/6667
# Password: mysecretpassword

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Project Structure

ft_irc/
├── Makefile
├── main.cpp
├── Includes/
│   ├── Server.hpp       # Server class declaration, IRC numeric codes
│   ├── Client.hpp       # Client class declaration, CommandType enum
│   └── Channel.hpp      # Channel class declaration
├── Server/
│   └── server.cpp       # Core server logic, connection handling
├── Client/
│   ├── Client.cpp       # Client implementation, utility functions
│   └── Commands/        # Command handlers (one per file)
│       ├── PASS.cpp     # Password authentication
│       ├── NICK.cpp     # Nickname registration
│       ├── USER.cpp     # User registration
│       ├── JOIN.cpp     # Join channel
│       ├── PART.cpp     # Leave channel
│       ├── PRIVMSG.cpp  # Private/channel messages
│       ├── KICK.cpp     # Kick user from channel
│       ├── INVITE.cpp   # Invite user to channel
│       ├── TOPIC.cpp    # View/set channel topic
│       ├── MODE.cpp     # Channel mode management
│       ├── QUIT.cpp     # Disconnect from server
│       └── PING.cpp     # Ping/pong keepalive
└── Channel/
    └── Channel.cpp      # Channel implementation

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IRC Commands

Registration Commands

PASS

Authenticate with the server password.

PASS <password>

• Must be sent before NICK and USER
• Error 462: Already registered
• Error 464: Password incorrect

NICK

Set or change nickname.

NICK <nickname>

• Nickname rules: 1-9 characters, starts with letter or underscore, alphanumeric with underscore/hyphen
• Error 431: No nickname given
• Error 432: Erroneous nickname
• Error 433: Nickname already in use

USER

Complete registration with username and realname.

USER <username> 0 * :<realname>

• Error 461: Not enough parameters
• Error 462: Already registered

Channel Commands

JOIN

Join one or more channels.

JOIN <channel>[,<channel>...] [<key>[,<key>...]]

• Creates channel if it doesn't exist (creator becomes operator)
• Channel names must start with # or &
• Error 403: No such channel
• Error 471: Channel is full (+l)
• Error 473: Invite only channel (+i)
• Error 475: Bad channel key (+k)

PART

Leave one or more channels.

PART <channel>[,<channel>...] [:<message>]

• Error 403: No such channel
• Error 442: You're not on that channel

TOPIC

View or set channel topic.

TOPIC <channel> [:<new topic>]

• Without topic: returns current topic
• With topic: sets new topic (if permitted)
• Error 442: You're not on that channel
• Error 482: You're not channel operator (when +t is set)
• Reply 331: No topic is set
• Reply 332: Current topic

KICK

Remove a user from a channel.

KICK <channel> <nickname> [:<reason>]

• Operators only
• Error 441: User not in channel
• Error 442: You're not on that channel
• Error 482: You're not channel operator

INVITE

Invite a user to a channel.

INVITE <nickname> <channel>

• Required for invite-only channels (+i)
• If +i is set, only operators can invite
• Error 401: No such nick
• Error 442: You're not on that channel
• Error 443: User already on channel
• Error 482: You're not channel operator

MODE

View or change channel modes.

MODE <channel> [<modes> [<parameters>]]

• Without modes: returns current mode string
• Operators only can change modes
• Error 482: You're not channel operator

Message Commands

PRIVMSG

Send a message to a user or channel.

PRIVMSG <target> :<message>

• Target can be nickname or channel name
• Error 401: No such nick/channel
• Error 404: Cannot send to channel (not a member)
• Error 411: No recipient given
• Error 412: No text to send

Connection Commands

QUIT

Disconnect from the server.

QUIT [:<message>]

• Notifies all channels the user was in
• Closes the connection

PING

Respond to server ping (keepalive).

PING <server>

• Server responds with PONG

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Channel Modes

Mode	Parameter	Description
+i	None	Invite-only - users must be invited to join
-i	None	Remove invite-only restriction
+t	None	Topic restricted - only operators can change topic
-t	None	Anyone can change topic
+k	key	Set channel password/key
-k	None	Remove channel password
+o	nickname	Give operator privilege to user
-o	nickname	Remove operator privilege from user
+l	limit	Set user limit (max members)
-l	None	Remove user limit

Examples:

MODE #channel +i                    # Set invite-only
MODE #channel +k secretpass         # Set channel key
MODE #channel +o username           # Make user an operator
MODE #channel +l 50                 # Limit to 50 users
MODE #channel +it                   # Set invite-only and topic restriction
MODE #channel -k                    # Remove channel key
MODE #channel +o-o user1 user2      # Give op to user1, remove from user2

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Numeric Reply Codes

Success Replies (001-099)

Code	Name	Description
001	RPL_WELCOME	Welcome message after registration
002	RPL_YOURHOST	Server host information
003	RPL_CREATED	Server creation date
004	RPL_MYINFO	Server name and version

Command Replies (300-399)

Code	Name	Description
324	RPL_CHANNELMODEIS	Current channel modes
331	RPL_NOTOPIC	No topic is set
332	RPL_TOPIC	Channel topic
341	RPL_INVITING	Invitation sent successfully
353	RPL_NAMREPLY	List of users in channel
366	RPL_ENDOFNAMES	End of /NAMES list

Error Replies (400-599)

Code	Name	Description
401	ERR_NOSUCHNICK	No such nick/channel
403	ERR_NOSUCHCHANNEL	No such channel
404	ERR_CANNOTSENDTOCHAN	Cannot send to channel
411	ERR_NORECIPIENT	No recipient given
412	ERR_NOTEXTTOSEND	No text to send
421	ERR_UNKNOWNCOMMAND	Unknown command
431	ERR_NONICKNAMEGIVEN	No nickname given
432	ERR_ERRONEUSNICKNAME	Erroneous nickname
433	ERR_NICKNAMEINUSE	Nickname is already in use
441	ERR_USERNOTINCHANNEL	User not in channel
442	ERR_NOTONCHANNEL	You're not on that channel
443	ERR_USERONCHANNEL	User is already on channel
451	ERR_NOTREGISTERED	You have not registered
461	ERR_NEEDMOREPARAMS	Not enough parameters
462	ERR_ALREADYREGISTRED	You may not reregister
464	ERR_PASSWDMISMATCH	Password incorrect
471	ERR_CHANNELISFULL	Channel is full
473	ERR_INVITEONLYCHAN	Invite only channel
475	ERR_BADCHANNELKEY	Bad channel key
482	ERR_CHANOPRIVSNEEDED	You're not channel operator

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Classes

Server (Singleton)

The main server class handling all connections and command routing.

Key Members:

• _listener - Listening socket file descriptor
• _pfds - Vector of pollfd structures for poll()
• _clients - Map of fd to Client objects
• _channels - Map of channel name to Channel objects
• _password - Server password
• _port - Server port

Key Methods:

• getInstance() - Get singleton instance
• run(port, password) - Start the server
• stop() - Stop the server
• handleNewConnection() - Accept new client connections
• handleClientData(fd) - Process incoming data from client
• routeCommand(fd, line) - Parse and route commands
• removeClient(fd) - Disconnect and clean up client
• getClientFdByNick(nickname) - Find client by nickname
• checkRegistration(fd) - Check if client can complete registration
• sendWelcome(fd) - Send welcome messages
• Command handlers: cmdPass, cmdNick, cmdUser, cmdJoin, cmdPart, cmdPrivmsg, cmdKick, cmdInvite, cmdTopic, cmdMode, cmdQuit, cmdPing

Client

Represents a connected IRC client.

Key Members:

• _fd - Client socket file descriptor
• _buffer - Incoming data buffer
• _nickname - Client nickname
• _username - Client username
• _realname - Client realname
• _hostname - Client IP address
• _channels - Set of joined channels
• _passOk - Password verification status
• _nickSet - Nickname set status
• _userSet - User info set status
• _registered - Full registration status

Key Methods:

• getPrefix() - Returns nick!user@host format
• appendToBuffer(data) - Append received data
• extractLine(line) - Extract complete line from buffer
• sendMessage(message) - Send message to client
• sendReply(server, code, message) - Send numeric reply
• canRegister() - Check if all registration conditions met
• tryRegister() - Attempt to complete registration
• addChannel(name) / removeChannel(name) - Manage channel membership

Static Utility Methods:

• isValidNickname(nickname) - Validate nickname format
• split(str, delim) - Split string by delimiter
• parseIRCLine(line, command, params) - Parse IRC protocol line
• getCommandType(command) - Convert command string to CommandType enum
• requiresRegistration(type) - Check if command requires registration

Channel

Represents an IRC channel.

Key Members:

• _name - Channel name
• _topic - Channel topic
• _key - Channel password
• _members - Set of member file descriptors
• _operators - Set of operator file descriptors
• _inviteList - Set of invited nicknames
• _inviteOnly - Invite-only mode flag
• _topicRestricted - Topic restriction flag
• _userLimit - Maximum members (0 = unlimited)

Key Methods:

• addMember(fd) / removeMember(fd) - Manage members
• isMember(fd) - Check membership
• addOperator(fd) / removeOperator(fd) - Manage operators
• isOperator(fd) - Check operator status
• addInvite(nickname) / removeInvite(nickname) - Manage invites
• isInvited(nickname) - Check if user is invited
• broadcast(message, excludeFd) - Send message to all members
• getModeString() - Get current modes as string

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Technical Details

Non-Blocking I/O

The server uses fcntl(fd, F_SETFL, O_NONBLOCK) to set all sockets to non-blocking mode. This allows the single-threaded server to handle multiple connections without blocking.

poll() Event Loop

A single poll() call monitors all file descriptors:

• Listening socket for new connections
• Client sockets for incoming data

Events are processed in the order returned by poll().

IRC Protocol

Messages follow the IRC protocol format:

[:prefix] COMMAND [params] [:trailing]

Lines are terminated with \r\n (CRLF).

Registration Flow

1. Client connects
2. Client sends PASS <password>
3. Client sends NICK <nickname>
4. Client sends USER <username> 0 * :<realname>
5. Server sends welcome messages (001-004)
6. Client is now registered and can use all commands

PASS must be sent before completing registration, but NICK and USER can be sent in any order.

Channel Creation

When a client joins a non-existent channel, the channel is created and the client becomes its first operator. Empty channels are automatically removed.

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Author

42 School Project - ft_irc

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License

This project is part of the 42 School curriculum.