🚀 ft_irc - IRC Server Implementation

A fully compliant, non-blocking IRC server built in C++98

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📋 Table of Contents

• Features
• Requirements
• Installation
• Usage
• Architecture
• Supported Commands
• Testing
• Technical Details
• Project Structure

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✨ Features

Core IRC Functionality

• ✅ Full Authentication - Password-protected server with PASS/NICK/USER registration
• ✅ Channel Management - Create, join, part channels with operator privileges
• ✅ Private Messaging - User-to-user and channel messaging (PRIVMSG/NOTICE)
• ✅ Channel Modes - Invite-only (+i), topic protection (+t), password (+k), user limit (+l), operator (+o)
• ✅ User Modes - Invisible (+i), wallops (+w), restricted (+r), operator (+o/O)
• ✅ Moderation Tools - KICK, INVITE, OPER, KILL commands
• ✅ Discovery - WHO, WHOIS, LIST, NAMES commands

Technical Excellence

• ✅ Non-blocking I/O - Single poll() call for all operations
• ✅ RFC Compliant - Follows IRC protocol specifications (RFC 1459/2812)
• ✅ Robust Parsing - Handles partial data, multiple line endings (CRLF/LF)
• ✅ Output Buffering - Queued sends with POLLOUT management
• ✅ Signal Handling - Graceful shutdown on SIGINT/SIGTERM
• ✅ Colored Logging - ANSI-colored server logs for debugging

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🔧 Requirements

• Compiler: g++ or clang++ with C++98 support
• OS: Linux (tested on Ubuntu/Debian)
• Build tool: make
• Client: Any IRC client (WeeChat, irssi, HexChat, nc)

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📦 Installation

# Clone the repository
git clone <your-repo-url> ft_irc
cd ft_irc

# Build the project
make

# The binary 'ircserv' will be created in the root directory

Compilation Flags

-Wall -Wextra -Werror -std=c++98 -g3

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🚀 Usage

Starting the Server

./ircserv <port> <password>

Example:

./ircserv 6667 mySecurePass123

Output:

[INFO] Starting IRC server on port 6667
[INFO] Password required for connection: mySecurePass123
[INFO] Listening on 0.0.0.0:6667
Press Ctrl+C to stop the server

Connecting with a Client

Using netcat (quick test)

nc 127.0.0.1 6667
PASS mySecurePass123
NICK alice
USER alice 0 * :Alice Wonderland
JOIN #general
PRIVMSG #general :Hello everyone!
QUIT :Goodbye

Using WeeChat

weechat
/server add local 127.0.0.1/6667 -password=mySecurePass123
/connect local
/nick alice
/join #general

Using irssi

irssi
/connect 127.0.0.1 6667 mySecurePass123 alice
/join #general

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🏗️ Architecture

Single Poll() Loop

┌──────────────────────────────────────────┐
│     Main Loop (Server::run)              │
│                                          │
│  while (!signal) {                       │
│      poll(_pfds, _nfds, 100ms);          │ ← ONE poll() call
│                                          │
│      if (POLLIN on listening socket)     │
│          → accept_new_clients()          │ (1 accept/cycle)
│                                          │
│      if (POLLIN on client socket)        │
│          → process_client_messages()     │ (1 read/client)
│                                          │
│      if (POLLOUT on client socket)       │
│          → flush output buffers          │ (1 send/client)
│  }                                       │
└──────────────────────────────────────────┘

Data Flow

Client → [recv] → inbuf → [parse] → Command → [process] → outbuf → [send] → Client

Key Design Decisions

1. Non-blocking I/O: All sockets use fcntl(fd, F_SETFL, O_NONBLOCK)
2. Input Buffering: Accumulates partial data until complete line (\r\n or \n)
3. Output Buffering: Queues messages, sends on POLLOUT readiness
4. Single Poll: Exactly one poll() call per event loop iteration
5. No errno loops: No EAGAIN checking to trigger re-reads (subject requirement)

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📡 Supported Commands

Authentication & Registration

Command	Description	Example
PASS	Set connection password	PASS mySecurePass123
NICK	Set/change nickname	NICK alice
USER	Set username and realname	USER alice 0 * :Alice W.
CAP	Capability negotiation	CAP LS

Channel Operations

Command	Description	Example
JOIN	Join channel(s)	JOIN #general,#random
PART	Leave channel(s)	PART #general :Goodbye
TOPIC	View/set channel topic	TOPIC #general :New topic
LIST	List all channels	LIST
NAMES	List channel members	NAMES #general

Messaging

Command	Description	Example
PRIVMSG	Send message	PRIVMSG #general :Hello!
NOTICE	Send notice (no auto-reply)	NOTICE alice :Info

Moderation & Admin

Command	Description	Example
KICK	Remove user from channel	KICK #general bob :Bad behavior
INVITE	Invite user to channel	INVITE alice #private
MODE	Change channel/user modes	MODE #general +it
OPER	Gain operator privileges	OPER admin pass
KILL	Disconnect user (oper only)	KILL bob :Abuse

Information

Command	Description	Example
WHO	Get user info	WHO #general
WHOIS	Detailed user info	WHOIS alice
PING	Keep-alive check	PING token
PONG	Response to PING	(automatic)

Other

Command	Description	Example
QUIT	Disconnect	QUIT :Bye
ERROR	Server error message	(server-sent)

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🧪 Testing

Manual Testing Scenarios

1. Basic Connection & Authentication

echo -e "PASS wrong\r\nQUIT\r\n" | nc 127.0.0.1 6667
# Expected: ERROR :Password incorrect

2. Multi-Client Chat

# Terminal 1
nc 127.0.0.1 6667
PASS mySecurePass123
NICK alice
USER alice 0 * :Alice
JOIN #test

# Terminal 2
nc 127.0.0.1 6667
PASS mySecurePass123
NICK bob
USER bob 0 * :Bob
JOIN #test
PRIVMSG #test :Hello alice!

3. Channel Modes

MODE #test +i          # Invite-only
MODE #test +t          # Topic protection
MODE #test +k secret   # Set password
MODE #test +l 10       # Max 10 users
MODE #test +o alice    # Give alice operator

4. Partial Data (Subject Requirement)

# Send command in fragments (simulating slow connection)
(printf "PA"; sleep 0.1; printf "SS pass"; sleep 0.1; printf "123\r\n") | nc 127.0.0.1 6667
# Expected: Server correctly assembles and processes "PASS pass123"

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🔍 Technical Details

Compliance with Subject Requirements

✅ Non-blocking I/O

• All sockets use O_NONBLOCK via fcntl(fd, F_SETFL, O_NONBLOCK)
• No other fcntl() usage (F_GETFL forbidden by subject)

✅ Single poll()

• Exactly 1 poll() call in entire codebase (src/Server.cpp:110)
• No select(), epoll(), or kqueue()
• Verify with: grep -r "poll(" src/

✅ poll() before I/O

• Every accept() preceded by POLLIN check
• Every read() preceded by POLLIN check
• Every send() preceded by POLLOUT check
• No errno checking for EAGAIN to trigger actions (forbidden by subject)

✅ Partial Data Handling

• Input buffer accumulates data until complete line
• Supports both \r\n (CRLF) and \n (LF) line endings
• Tested with fragmented input (see test_partial_data.sh)

Error Handling

• Socket errors: Logged and client disconnected
• Unknown commands: 421 ERR_UNKNOWNCOMMAND
• Missing parameters: 461 ERR_NEEDMOREPARAMS
• Privilege errors: 481/482 ERR_NOPRIVILEGES
• Channel errors: 403/471/473/475 (No such channel, full, invite-only, bad key)

Logging System

Color-coded server logs for debugging:

• 🔵 [INFO] - Server startup/status (blue)
• 🟢 [AUTH] - Authentication events (green)
• 🟡 [CHANNEL] - Channel operations (yellow)
• 🔴 [ERROR] - Errors (red)
• 🟣 [CMD] - Commands received (magenta)
• 🔵 [STATE] - Server state (blue)
• 🟠 [CONNECT] - New connections (cyan)
• 🟡 [DISCONNECT] - Client disconnections (yellow)

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📁 Project Structure

ft_irc/
├── inc/                          # Header files
│   ├── Channel.hpp              # Channel management
│   ├── Client.hpp               # Client structure
│   ├── Commands.hpp             # Command handler class
│   ├── Message.hpp              # IRC message parser
│   ├── Server.hpp               # Main server class
│   ├── config.hpp               # Constants (MAX_CLIENTS, BUFFER_SIZE)
│   ├── ft_irc.hpp               # Common includes
│   └── utils.hpp                # Utility functions
│
├── src/                          # Source files
│   ├── main.cpp                 # Entry point
│   ├── Server.cpp               # Server implementation (poll loop)
│   ├── Client.cpp               # Client methods
│   ├── Channel.cpp              # Channel methods
│   ├── Message.cpp              # IRC message parsing
│   ├── Commands.cpp             # Command dispatcher
│   ├── utils.cpp                # Helper functions
│   │
│   └── commands/                # Individual command handlers
│       ├── CAP.cpp              # Capability negotiation
│       ├── PASS.cpp             # Password authentication
│       ├── NICK.cpp             # Nickname management
│       ├── USER.cpp             # User registration
│       ├── JOIN.cpp             # Channel joining (multi-channel support)
│       ├── PART.cpp             # Channel leaving (multi-channel support)
│       ├── TOPIC.cpp            # Topic management
│       ├── MODE.cpp             # Mode changes (channel & user)
│       ├── PRIVMSG_NOTICE.cpp   # Messaging
│       ├── INVITE_KICK.cpp      # Moderation
│       ├── OPER.cpp             # Operator authentication
│       ├── KILL.cpp             # Force disconnect
│       ├── WHO_WHOIS.cpp        # User information
│       ├── LIST_NAMES.cpp       # Channel listing
│       ├── PING_PONG.cpp        # Keep-alive
│       ├── QUIT.cpp             # Disconnect
│       └── ERROR.cpp            # Error handling
│
├── Makefile                      # Build configuration

Key Classes

• Server: Main event loop, socket management, poll() handling
• Client: Client state (fd, nick, user, modes, buffers)
• Channel: Channel state (name, topic, modes, users, operators)
• Message: IRC message parser (command, params, trailing)
• Commands: Command dispatcher and handlers

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📊 Configuration

Edit inc/config.hpp to customize:

#define MAX_CLIENTS 100          // Maximum simultaneous clients
#define BUFFER_SIZE 4096         // Read buffer size

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🐛 Known Limitations

Intentional (Subject Constraints)

• Single server (no server-to-server linking)
• No SSL/TLS support
• No services (NickServ, ChanServ)
• Minimal capability negotiation (CAP)

🎯 Subject Compliance Checklist

Mandatory Part

• ./ircserv <port> <password> usage
• Non-blocking I/O on all operations
• One single poll() (or equivalent)
• poll() called before each accept/read/recv/write/send
• No other fcntl() usage
• No errno checks after I/O operations
• TCP/IP (v4) sockets
• Multiple clients without hanging
• No forking
• Partial data handling
• Low bandwidth client support
• Client-to-client communication
• Authentication (password, nickname, username)
• Channel operations (join, send/receive messages)
• Forward messages to all channel clients
• Distinguish operators from regular users
• Operator-only commands implementation

Commands Implemented

• PASS - Password authentication
• NICK - Set nickname
• USER - Set username
• JOIN - Join channels
• PART - Leave channels
• PRIVMSG - Send messages
• NOTICE - Send notices
• KICK - Kick user (operator)
• INVITE - Invite to channel (operator)
• TOPIC - View/set topic (operator if +t)
• MODE - Channel/user modes (operator)
• PING/PONG - Keep-alive

Channel Modes

• +i - Invite-only channel
• +t - Topic restriction (operators only)
• +k - Channel password
• +o - Operator privileges
• +l - User limit

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📚 Resources

• RFC 1459 - Original IRC Protocol
• RFC 2812 - IRC Client Protocol
• RFC 2813 - IRC Server Protocol
• Modern IRC Documentation
• Numeric Replies Reference

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