🚀 LAN Messenger

A high-performance, multi-threaded chat application built in C using TCP sockets. Features real-time messaging, colorful terminal output, and robust client-server architecture.

✨ Features

• Real-time messaging - Instant private messaging between connected clients
• Multi-threaded architecture - Handles up to 50 concurrent connections
• Thread-safe operations - Mutex-protected client management
• Unique ID system - Auto-generated 4-digit IDs for each user
• Graceful disconnection - Clean shutdown with proper resource cleanup
• Debug mode - Comprehensive logging for development and troubleshooting

🛠️ Build & Run

Join a server

use this command to join a server

if executed type in the server ip address

bash <(curl -L https://raw.githubusercontent.com/4n4k1n/LAN-messenger/refs/heads/main/setup.sh)

Quick Start

# Clone the repository
git clone https://github.com/4n4k1n/LAN-messenger.git
cd LAN-messenger

# Build the application
make

# Run the server (in one terminal)
./server

# Connect clients (in separate terminals)
./client

Build Options

make              # Standard build
make all          # Same as make
make debug        # Build with colorful debug messages
make server       # Build server only
make client       # Build client only
make clean        # Clean build artifacts
make fclean       # Full clean (removes executables)

🎮 Usage

Starting the Server

./server

Server starts on 127.0.0.1:12345 and displays status messages.

Connecting Clients

./client

Available Commands:

• @username#id message - Send private message
• /list - Show online users
• /quit - Exit gracefully

Example Session

Enter username: Anakin
Logging in...

=== Personal Messages ===
You are: Anakin#1234

Commands:
  @username#id message  - Send private message
  /list                 - Show online users
  /quit                 - Exit

================================

> /list
Online users:
  Anakin#1234
  Korb#5678
Total: 2 user(s) online

> @Korb#5678 Hello there!
[You → Korb#5678]: Hello there!

> [Korb#5678 → You]: Hi Anakin!

🏗️ Architecture

Server Components

• Main server thread - Accepts new connections and manages client pool
• Client handler threads - One dedicated thread per connected client
• Thread-safe client management - Mutex-protected operations for up to 50 clients
• Message routing system - Direct messaging and broadcast notifications

Client Components

• Main client thread - Handles user input and connection management
• Receive thread - Continuously listens for incoming messages
• Message parser - Parses @username#id message format

Network Protocol

Login:     LOGIN:username
Private:   PRIVATE:target_name:target_id:message
List:      LIST
Quit:      QUIT

Responses:
WELCOME:username:id
MSG:sender#id:message
SENT:receiver#id:message
LIST:user1#id1,user2#id2,...
ERROR:error_message
NOTIFY:notification

🔧 Technical Details

Requirements

• Compiler: GCC with C99 support
• Libraries: pthread, standard C library
• Platform: Linux/Unix-like systems
• Memory: Address sanitizer enabled for debugging

Thread Safety

• Mutex-protected client array operations
• Thread-safe message routing
• Proper resource cleanup on disconnection

Memory Management

• Dynamic memory allocation for message parsing
• Automatic cleanup on client disconnect
• Address sanitizer for memory leak detection

📁 Project Structure

LAN-messenger/
├── inc/
│   └── messenger.h          # Header with prototypes and constants
├── src/
│   ├── server/
│   │   ├── server.c         # Main server logic
│   │   └── accept_client.c  # Client connection handling
│   └── client/
│       ├── client.c         # Main client logic
│       ├── receive_msg.c    # Message receiving thread
│       └── parse_msg.c      # Message parsing utilities
├── Dockerfile               # Container config
├── docker-compose.yml       # Compose file
├── Makefile                 # Build configuration
├── setup.sh                 # script to start a client
└── README.md                # This file

🚀 Development

Debug Mode

Enable debug mode for detailed logging:

make debug
./server    # Shows debug messages
./client    # Also shows debug info

Adding Features

1. Follow existing code patterns in src/
2. Update function prototypes in inc/messenger.h
3. Maintain thread safety with proper mutex usage
4. Test with multiple clients for concurrency issues

📜 License

This project is open source and available under the MIT License.

🙏 Acknowledgments

• Built with modern C programming practices
• Thread-safe design patterns
• TCP socket programming fundamentals