IRC Server - 42 Project

A complete IRC (Internet Relay Chat) server implementation in C++ that follows the RFC 1459 protocol specification. This server handles multiple client connections, channel management, and real-time messaging.

🚀 Features

• Multi-client Support: Handles multiple simultaneous client connections using poll()
• Channel Management: Create, join, and manage IRC channels with various modes
• User Authentication: Password-based server authentication
• Real-time Messaging: Private messages and channel broadcasts
• Channel Modes: Invite-only, password-protected, user limits, topic restrictions
• Admin Controls: Channel operators with kick, invite, and mode management capabilities
• Signal Handling: Graceful shutdown with SIGINT, SIGQUIT, and SIGPIPE handling

🏗️ Architecture

Server Architecture

┌─────────────────┐    ┌─────────────────┐    ┌─────────────────┐
│   IRC Client    │    │   IRC Client    │    │   IRC Client    │
│   (nc/HexChat)  │    │   (nc/HexChat)  │    │   (nc/HexChat)  │
└─────────┬───────┘    └─────────┬───────┘    └─────────┬───────┘
          │                      │                      │
          └──────────────────────┼──────────────────────┘
                                 │
                    ┌─────────────▼─────────────┐
                    │      IRC Server           │
                    │  ┌─────────────────────┐  │
                    │  │   Main Server Loop  │  │
                    │  │   (poll-based)      │  │
                    │  └─────────────────────┘  │
                    │  ┌─────────────────────┐  │
                    │  │   Command Parser    │  │
                    │  └─────────────────────┘  │
                    │  ┌─────────────────────┐  │
                    │  │   Channel Manager   │  │
                    │  └─────────────────────┘  │
                    │  ┌─────────────────────┐  │
                    │  │   Client Manager    │  │
                    │  └─────────────────────┘  │
                    └───────────────────────────┘

🔧 Connection Handling Details

1. TCP Protocol Overview

The server uses TCP (Transmission Control Protocol) for reliable, ordered communication:

┌─────────────┐    TCP Handshake   ┌─────────────┐
│   Client    │◄──────────────────►│   Server    │
│             │   SYN, SYN-ACK,    │             │
│             │      ACK           │             │
└─────────────┘                    └─────────────┘
       │                                   │
       │        Data Transfer              │
       │◄─────────────────────────────────►│
       │    (IRC Commands/Responses)       │
       │                                   │
       │        Connection Close           │
       │◄─────────────────────────────────►│

TCP Features Used:

• Reliable Delivery: All IRC messages arrive in order
• Connection-oriented: Persistent connections for real-time chat
• Full-duplex: Bidirectional communication (client ↔ server)
• Error Detection: Automatic retransmission of lost packets

2. Server Initialization

The server uses a non-blocking socket with poll() for efficient I/O multiplexing:

// Socket creation and setup
server_socket = socket(AF_INET, SOCK_STREAM, 0);
fcntl(server_socket, F_SETFL, O_NONBLOCK);  // Non-blocking mode
bind(server_socket, (struct sockaddr *)&server_address, sizeof(server_address));
listen(server_socket, SOMAXCONN);

3. Command Processing Pipeline

Raw Data → Buffer Split → Command Parsing → Handler Execution → Response
    ↓           ↓              ↓                ↓              ↓
  recv()    SplitBuffer()   Parser.cpp    ACommands.cpp   sendResponse()

📁 Project Structure

42.irc/
├── main.cpp                 # Entry point
├── Makefile                 # Build configuration
├── includes/
│   ├── Libraries.hpp        # Common includes and macros
│   ├── Server.hpp          # Server class definition
│   ├── Client.hpp          # Client class definition
│   ├── Channel.hpp         # Channel class definition
│   ├── ACommands.hpp       # Command interface
│   └── Parser.hpp          # Command parser
├── src/
│   ├── Server.cpp          # Server implementation
│   ├── Client.cpp          # Client implementation
│   ├── Channel.cpp         # Channel implementation
│   ├── Parser.cpp          # Command parsing logic
│   └── cmds/               # Command implementations
│       ├── Join.cpp        # Channel joining
│       ├── Privmsg.cpp     # Private messaging
│       ├── Kick.cpp        # User kicking
│       ├── Mode.cpp        # Channel modes
│       ├── Nick.cpp        # Nickname changes
│       ├── Pass.cpp        # Password authentication
│       ├── User.cpp        # User registration
│       └── ...             # Other commands

🛠️ Building and Running

Prerequisites

• C++98 compatible compiler (g++)
• Linux/Unix system
• netcat (for testing)

Build

make

Run

./ircserv <port> <password>

Example:

./ircserv 6667 mypassword

Test with netcat

nc localhost 6667

📋 Supported Commands

Command	Description	Example
PASS	Server password authentication	PASS mypassword
NICK	Set nickname	NICK alice
USER	Register username	USER alice 0 * :Alice Smith
JOIN	Join/create channel	JOIN #general
PRIVMSG	Send private message	PRIVMSG #general :Hello!
KICK	Kick user from channel	KICK #general bob :Bad behavior
MODE	Set channel modes	MODE #general +i
TOPIC	Set channel topic	TOPIC #general :Welcome to general chat
INVITE	Invite user to channel	INVITE bob #general
PART	Leave channel	PART #general
QUIT	Disconnect from server	QUIT :Goodbye!

🔒 Channel Modes

• +i: Invite-only channel
• +k: Password-protected channel
• +l: User limit
• +t: Topic restriction (only ops can change)

🧪 Testing

Basic Connection Test

# Terminal 1: Start server
./ircserv 6667 testpass

# Terminal 2: Connect with netcat
nc localhost 6667
PASS testpass
NICK alice
USER alice 0 * :Alice Smith

Channel Operations Test

# Join a channel
JOIN #test

# Send a message
PRIVMSG #test :Hello everyone!

# Set channel mode
MODE #test +i

🚨 Error Handling

The server implements comprehensive error handling:

• Connection errors: Graceful client disconnection
• Protocol errors: Proper IRC error responses
• Signal handling: Clean shutdown on SIGINT/SIGQUIT
• Memory management: Proper cleanup of resources

📚 Protocol Compliance

This implementation follows RFC 1459 IRC protocol specifications:

• Proper message formatting with CRLF line endings
• Standard IRC numeric replies
• Channel naming conventions (#channel)
• User registration flow (PASS → NICK → USER)