This project has been created as part of the 42 curriculum by marcoga2, mvassall, jrollon-.

🌐 ft_irc — IRC Server

An IRC (Internet Relay Chat) server implementation written in C++98, following the specifications defined in RFC 2810, RFC 2811, and RFC 2812. The server is designed to handle multiple concurrent clients using non-blocking I/O with the epoll event-driven mechanism on Linux.

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📖 Description

ft_irc is a 42 school project whose goal is to build a fully functional IRC server from scratch in C++98. The server enables real-time text-based communication between multiple clients through channels and private messages, just like classic IRC networks.

The server accepts connections from any standard IRC client (such as irssi, WeeChat, HexChat, or netcat) and implements the core subset of the IRC protocol required for:

• User authentication via password, nickname, and username registration.
• Channel management including creation, joining, leaving, topic setting, and user listing.
• Private messaging between users and to channels.
• Channel operator privileges with mode management.
• Graceful disconnection and timeout handling.

Key Highlights

• Single-threaded, event-driven architecture using epoll for high-performance I/O multiplexing.
• Non-blocking sockets with edge-triggered events.
• Full message parsing compliant with the IRC protocol (prefix, command, parameters).
• Per-client input/output buffering to handle partial reads and writes.
• Client inactivity timeout detection with server-initiated PING/PONG.
• Comprehensive numeric reply codes as specified in RFC 2812.

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✨ Features

Implemented IRC Commands

Command	Description
PASS	Authenticate with the server password
NICK	Set or change nickname
USER	Set username and real name during registration
QUIT	Disconnect from the server
JOIN	Join one or more channels (with optional key)
PART	Leave one or more channels
PRIVMSG	Send a message to a user or channel
NOTICE	Send a notice (no automatic reply)
TOPIC	View or set the channel topic
NAMES	List users in a channel
WHO	Query information about channel members
MODE	Query or change channel/user modes
PING	Client-initiated keepalive
PONG	Server response to PING
CAP	Capability negotiation (minimal support)

Supported Channel Modes

Mode	Flag	Description
Invite-only	+i	Only invited users can join the channel
Topic protection	+t	Only channel operators can change the topic
Key (password)	+k	Requires a password to join the channel
User limit	+l	Limits the maximum number of users in the channel
Operator	+o	Grant or revoke channel operator privileges

Channel Features

• Channels must start with #, &, +, or ! (as per RFC 2811).
• Channel names are case-insensitive (stored in lowercase internally).
• Maximum channel name length: 50 characters.
• The first user to join a channel is automatically promoted to channel operator (@).
• Operators can kick users, set modes, change topics, and manage invitations.

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🏗️ Architecture

Project Structure

irc-server/
├── include/                 # Header files
│   ├── IRCServ.hpp          # Main server class
│   ├── IRCClient.hpp        # Client representation
│   ├── IRCChannel.hpp       # Channel management
│   ├── IRCCommand.hpp       # IRC command/reply code enums
│   ├── IRCMessage.hpp       # IRC message parser
│   └── utils.hpp            # Utility functions
├── src/                     # Source files
│   ├── main.cpp             # Entry point
│   ├── IRCServ.cpp          # Server core (socket, epoll, event loop)
│   ├── IRCClient.cpp        # Client state management
│   ├── IRCChannel.cpp       # Channel logic
│   ├── IRCCommand.cpp       # Command string ↔ enum mapping
│   ├── IRCMessage.cpp       # Message parsing (prefix, command, params)
│   ├── answer_auth.cpp      # PASS, NICK, USER, QUIT handlers
│   ├── answer_join.cpp      # JOIN command handler
│   ├── answer_part.cpp      # PART command handler
│   ├── answer_mode.cpp      # MODE command handler
│   ├── answer_topic.cpp     # TOPIC command handler + broadcastToChannel
│   ├── answer_names.cpp     # NAMES command handler
│   ├── answer_who.cpp       # WHO command handler
│   └── utils.cpp            # Utility function implementations
├── Documentacion/           # Internal documentation & references
│   ├── answer_table.md      # Command behavior reference table
│   └── RFC 2812.html        # Redirect to RFC 2812
├── pcap-files/              # Packet capture files for debugging
├── Makefile                 # Build system
└── README.md                # This file

Core Classes

Class	Responsibility
IRCServ	Main server: socket creation, epoll event loop, connection management, command dispatching, message sending/broadcasting
IRCClient	Represents a connected client: nickname, username, fullname, host, file descriptor, flags (PASS/NICK/USER/REGISTERED), input/output buffers, channel membership, timeout tracking
IRCChannel	Represents a channel: name, user map with modes (operator/regular), channel modes (invite-only, topic, key, user limit), topic, invited nicks list, creation metadata
IRCMessage	Parses raw IRC protocol strings into structured objects (prefix, command, parameters) following the :[prefix] COMMAND [params] :[trailing] format
IRCCommand	Enum of all RFC 2812 commands and numeric reply/error codes, with bidirectional string-to-enum conversion

Event Loop Flow

1. epoll_wait() blocks until events are ready
2. For each event:
   a. If event on listening_socket → accept_new_connection()
   b. If EPOLLIN on client fd → read_from_client() → process_client_buffer()
      → parse messages → answer_command() for each complete message
   c. If EPOLLOUT on client fd → flush output buffer to socket
3. Check for clients scheduled for removal (graceful cleanup)
4. Repeat

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🔧 Instructions

Prerequisites

• Operating System: Linux (required for epoll).
• Compiler: c++ (g++ or clang++) with C++98 support.
• Make: GNU Make.

Compilation

Clone the repository and build:

git clone https://github.com/mvg001/irc-server.git
cd irc-server
make

This compiles the project with the following flags:

• -Wall -Werror -Wextra — strict warnings
• -std=c++98 -pedantic — C++98 standard compliance
• -g3 -fsanitize=address — debug symbols and address sanitizer (development mode)

Makefile Targets

Target	Description
make or make all	Build the ircserv binary
make clean	Remove object files
make fclean	Remove object files and the binary
make re	Full rebuild (fclean + all)

Execution

./ircserv <port> <password>

Parameter	Description
port	The TCP port number the server will listen on (e.g., 6667)
password	The connection password clients must provide via PASS

Example:

./ircserv 6667 mypassword

Connecting with an IRC Client

Using irssi

irssi
/connect 127.0.0.1 6667 mypassword
/nick MyNick

Using netcat (for testing)

nc 127.0.0.1 6667
PASS mypassword
NICK testuser
USER testuser 0 * :Test User
JOIN #general
PRIVMSG #general :Hello, world!

Using WeeChat

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

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💡 Usage Examples

Creating and Joining a Channel

PASS mypassword
NICK alice
USER alice 0 * :Alice Wonderland
JOIN #wonderland

Sending Messages

PRIVMSG #wonderland :Hello everyone!
PRIVMSG bob :Hey Bob, private message!

Setting Channel Modes (as Operator)

MODE #wonderland +t          # Only operators can change topic
MODE #wonderland +i          # Invite-only channel
MODE #wonderland +k secret   # Set channel password to "secret"
MODE #wonderland +l 10       # Limit channel to 10 users
MODE #wonderland +o bob      # Give operator status to bob
MODE #wonderland -o bob      # Remove operator status from bob

Changing the Topic

TOPIC #wonderland :Welcome to Wonderland!
TOPIC #wonderland               # Query current topic

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🛠️ Technical Choices

Decision	Rationale
C++98 standard	Required by the 42 project subject to ensure compatibility and mastery of classic C++
epoll (Linux)	Provides efficient, scalable I/O multiplexing for handling many simultaneous connections with O(1) event notification
Non-blocking sockets	Prevents any single client from stalling the entire server; combined with edge-triggered epoll for maximum performance
Single-threaded	Simplifies state management and avoids concurrency bugs; the event-driven model handles concurrency at the I/O level
Per-client I/O buffers	Handles partial TCP reads/writes gracefully — messages are accumulated in the input buffer and flushed from the output buffer as the socket becomes writable
SIGPIPE ignored	Prevents the server from crashing when writing to a disconnected client socket; errors are handled in the send logic instead
Client timeout (120s)	Server sends PING to inactive clients and disconnects them if no PONG is received, ensuring stale connections are cleaned up
Case-insensitive channels	Channel names are stored in lowercase internally, following IRC convention

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📚 Resources

RFC Documents (Primary References)

• RFC 2810 — Internet Relay Chat: Architecture — Overview of the IRC architecture.
• RFC 2811 — Internet Relay Chat: Channel Management — Channel types, modes, and management.
• RFC 2812 — Internet Relay Chat: Client Protocol — The main reference for client-server message format, commands, and numeric replies.
• RFC 2813 — Internet Relay Chat: Server Protocol — Server-to-server communication (not implemented, for context only).

Tutorials & Articles

• Beej's Guide to Network Programming — Essential reference for socket programming in C/C++.
• The epoll man page — Linux epoll API documentation.
• Modern IRC Documentation — Community-maintained, modern take on IRC protocol documentation.
• IRC Numerics List — Comprehensive list of IRC numeric reply codes.
• Chirc — An IRC Server Project — University of Chicago's IRC server project, useful as a learning reference.

Tools Used for Development & Testing

• Wireshark / tcpdump — Network packet analysis (pcap files included in the repository for reference).
• irssi / WeeChat / HexChat — IRC clients used for integration testing.
• netcat (nc) — Raw TCP client used for manual protocol testing.
• ngircd — Reference IRC server used to compare expected behavior and responses.

AI Usage Disclosure

AI tools (specifically GitHub Copilot) were used during the development of this project for the following tasks:

• Code autocompletion: Assisted with repetitive boilerplate code such as getters/setters, constructor initializer lists, and copy constructors following the Orthodox Canonical Form.
• Documentation generation: Helped draft this README.md file based on the existing codebase structure and content.
• Debugging assistance: Consulted for understanding specific IRC numeric reply codes and their expected format.
• Reference lookups: Used to quickly find the correct RFC sections for specific command behaviors.

All core logic — including the server architecture, epoll event loop, message parsing, command handlers, channel mode system, and client management — was designed, implemented, and debugged by the team members.

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👥 Authors

42 Login	GitHub	Role
mvassall	@mvg001	Developer
marcoga2	@marcogmurciano	Developer
jrollon-	@JRM32	Developer

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📄 License

This project was developed as part of the 42 school curriculum. It is intended for educational purposes.