ft_irc

📖 About

"ft_irc" is a project at 42 Madrid that involves creating an IRC (Internet Relay Chat) server written in C++98. This project introduces network programming fundamentals, non-blocking I/O multiplexing, and teaches how to implement a real-time communication protocol that can be tested with any standard IRC client.

The goal is to implement a fully functional server that handles multiple simultaneous clients, supports authentication, channel management, private messaging, and operator privileges, all through a single poll() event loop without forking.

🎯 Objectives

• Understanding TCP/IP socket programming and client-server architecture
• Implementing non-blocking I/O multiplexing with poll()
• Learning the IRC protocol (RFC 1459 / RFC 2812)
• Managing concurrent connections and partial data buffering
• Implementing authentication, user registration, and channel management
• Handling operator privileges and channel modes
• Writing robust, crash-resistant network code in C++98

📋 Function Overview

ft_irc

Feature	Description
Non-blocking Server	Single poll() event loop handling all I/O operations
Authentication	Password-based connection authentication
User Registration	PASS/NICK/USER registration flow with welcome messages
Channel System	Create, join, part channels with # or & prefix
Private Messaging	Direct messages between users via PRIVMSG
Channel Messaging	Broadcast messages to all channel members
Operator System	Channel operators with elevated privileges
Channel Modes	Five configurable channel modes (i, t, k, o, l)
Invite System	Invite users to channels, with invite-only support
Topic Management	View and set channel topics with optional restriction
Kick Command	Operators can remove users from channels
Partial Data Handling	Aggregates TCP packets before processing commands
Graceful Shutdown	SIGINT handler for clean server termination

Usage Example & Testing

Quick Start

1. Compile and launch the server:

make && ./ircserv 6667 mypassword

2. Connect with a client (open another terminal):

# Using socat
socat - TCP:127.0.0.1:6667

3. Register and chat:

PASS mypassword
NICK alice
USER alice 0 * :Alice Smith
JOIN #test
PRIVMSG #test :Hello from alice!

Multi-client Test

Open three terminals to simulate a full chat scenario:

Terminal 1 - Server:

./ircserv 6667 secret

Terminal 2 - Client A:

socat - TCP:127.0.0.1:6667
PASS secret
NICK alice
USER alice 0 * :Alice
JOIN #general
PRIVMSG #general :Hi everyone!

Terminal 3 - Client B:

socat - TCP:127.0.0.1:6667
PASS secret
NICK bob
USER bob 0 * :Bob
JOIN #general
PRIVMSG #general :Hey alice!
PRIVMSG alice :This is a private message

Testing Channel Modes

# alice creates a channel (becomes operator automatically)
JOIN #secret

# Set invite-only + password + user limit
MODE #secret +ikl key123 10

# Set topic (operator only when +t is set)
TOPIC #secret :Welcome to the secret channel

# Invite bob
INVITE bob #secret

# bob joins with key
JOIN #secret key123

# Give bob operator status
MODE #secret +o bob

# Kick bob
KICK #secret bob :reason here

Testing with irssi

irssi -c 127.0.0.1 -p 6667 -w mypassword -n mynick

Once connected:

/join #test
/msg #test Hello!
/msg othernick Private hello
/topic #test New topic
/mode #test +i
/invite othernick #test
/kick #test othernick reason
/quit bye

Graceful Shutdown

Press Ctrl+C on the server terminal to trigger a clean shutdown via SIGINT.

🚀 Installation & Structure

📥 Compilation & Usage

Build

make        # Compile the project
make clean  # Remove object files
make fclean # Full cleanup (objects + binary)
make re     # Recompile from scratch

Usage

./ircserv <port> <password>

Argument	Range	Description
port	1 - 65535	TCP port to listen on
password	non-empty	Connection password for clients

Supported IRC Commands

Command	Parameters	Description
PASS	<password>	Authenticate with the server
NICK	<nickname>	Set or change nickname (max 9 chars)
USER	<user> <mode> <unused> :<realname>	Set username and real name
JOIN	<channel>[,<channel>] [<key>[,<key>]]	Join one or more channels
PART	<channel>[,<channel>] [:<reason>]	Leave one or more channels
PRIVMSG	<target> :<message>	Send a message to user or channel
NOTICE	<target> :<message>	Send a notice (no auto-reply)
KICK	<channel> <user> [:<reason>]	Remove a user from a channel
INVITE	<nickname> <channel>	Invite a user to a channel
TOPIC	<channel> [:<topic>]	View or set the channel topic
MODE	<channel> [<flags> [<params>]]	View or change channel modes
PING	<token>	Connection keepalive
QUIT	[:<message>]	Disconnect from the server

Channel Modes

Mode	Parameter	Description
i	none	Set/remove invite-only channel
t	none	Restrict TOPIC changes to operators
k	<key>	Set/remove channel password
o	<nickname>	Give/take channel operator status
l	<limit>	Set/remove maximum user count

Connecting with an IRC Client

irssi:

irssi -c 127.0.0.1 -p 6667 -w mypassword

WeeChat:

/server add local 127.0.0.1/6667 -password=mypassword
/connect local

HexChat: Set server to 127.0.0.1/6667, server password to mypassword.

Testing with socat:

socat - TCP:127.0.0.1:6667
PASS mypassword
NICK testuser
USER testuser 0 * :Test User
JOIN    #general
PRIVMSG #general :Hello everyone!
QUIT :bye

📁 Project Structure

ft_irc/
│
├── docs/
│   └── README.md                # Mandatory project documentation
├── include/
│   ├── Irc.hpp                  # Main header: standard includes, defines, forward declarations
│   ├── Replies.hpp              # IRC numeric reply constants (RPL:: and ERR:: namespaces)
│   ├── Server.hpp               # Server class: poll loop, command dispatch, helpers
│   ├── Client.hpp               # Client class: connection state, buffer, identity
│   └── Channel.hpp              # Channel class: membership, modes, relay
├── src/
│   ├── main.cpp                 # Entry point, argument validation, signal handlers
│   ├── Server.cpp               # Constructor, destructor, boot(), run(), helper methods
│   ├── Network.cpp              # Socket setup, accept, receive with buffering, disconnect
│   ├── Client.cpp               # Client state management, OCF, fullId() prefix
│   ├── Channel.cpp              # Channel membership, operator management, broadcast
│   ├── Parse.cpp                # IRC message parser, command dispatcher, registration check
│   ├── CmdAuth.cpp              # PASS, NICK, USER, QUIT, PING command handlers
│   ├── CmdChannel.cpp           # JOIN, PART, TOPIC, MODE (with decomposed sub-handlers)
│   └── CmdMessage.cpp           # PRIVMSG, NOTICE, KICK, INVITE command handlers
├── .gitignore
├── Makefile
└── README.md                    # Project documentation

💡 Key Learning Outcomes

The ft_irc project teaches fundamental network programming and protocol implementation:

• Socket Programming: Creating, binding, and listening on TCP sockets
• I/O Multiplexing: Using poll() to handle multiple file descriptors in a single thread
• Non-blocking I/O: Setting sockets to non-blocking mode with fcntl()
• Protocol Implementation: Parsing and responding to IRC protocol messages
• Buffer Management: Handling partial TCP reads and command reconstruction
• State Management: Tracking client registration, channel membership, and operator status
• Signal Handling: Graceful shutdown with SIGINT, ignoring SIGPIPE for broken connections
• Memory Management: Proper cleanup of dynamically allocated clients and channels

⚙️ Technical Specifications

• Language: C++ (C++98 standard)
• Compiler: c++ with -Wall -Wextra -Werror -std=c++98
• I/O Model: Single-threaded, non-blocking with poll()
• Protocol: IRC (RFC 1459 / RFC 2812 subset)
• Transport: TCP/IP (IPv4)
• Max Connections: 128
• Buffer Size: 512 bytes per read, 4096 bytes max per client
• Nickname Length: 9 characters maximum

🔧 Requirements

• Linux or macOS
• C++ compiler with C++98 support
• Make
• An IRC client for testing (irssi, WeeChat, HexChat, or socat/netcat)

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Note

This project provides hands-on experience with network programming, protocol design, and concurrent connection handling, demonstrating proficiency in systems-level C++ programming.