Minitalk

A simple client-server communication program that transmits messages using only UNIX signals.

📋 Description

Minitalk is a project that demonstrates inter-process communication (IPC) using UNIX signals. The program consists of a server (listener) and a client (speaker) that communicate by encoding text messages into binary and transmitting them bit-by-bit using SIGUSR1 and SIGUSR2 signals.

How it works:

• Server (listener): Displays its PID and waits to receive messages
• Client (speaker): Takes a message and sends it to the server using the server's PID
• Each character is broken down into 8 bits
• SIGUSR1 represents bit 0
• SIGUSR2 represents bit 1
• Server reconstructs the message from received bits and displays it

🚀 Features

• ✅ Reliable message transmission with acknowledgment system
• ✅ Bit-level manipulation for character encoding
• ✅ Asynchronous signal handling
• ✅ Support for extended ASCII characters
• ✅ Clean error handling

🛠️ Installation

# Clone the repository
git clone https://github.com/ccakirr/minitalk.git
cd minitalk

# Compile the project
make

This will create two executables: listener (server) and speaker (client).

📖 Usage

Starting the Server

./listener

The server will display its PID:

Server PID: 12345

Sending a Message

./speaker [SERVER_PID] "Your message here"

Example:

./speaker 12345 "Hello, World!"

The message will appear on the server terminal.

🔧 Compilation

Available Makefile rules:

• make - Compile both server and client
• make clean - Remove object files
• make fclean - Remove object files and executables
• make re - Recompile everything

📚 Technical Details

Signal Flow

1. Client converts each character to binary (8 bits)
2. For each bit:
   • Sends SIGUSR1 for 0
   • Sends SIGUSR2 for 1
3. Server receives signal and reconstructs the bit
4. Server sends acknowledgment back to client
5. After 8 bits, server displays the character

Libraries Used

• libft - Custom C library
• ft_printf - Custom printf implementation
• Standard signal handling functions

🎓 Learning Outcomes

This project teaches:

• UNIX signal handling
• Inter-process communication
• Bit manipulation
• Asynchronous programming
• Signal safety considerations

⚙️ Requirements

• Unix-based operating system (Linux, macOS)
• GCC compiler
• Make

📝 Project Structure

minitalk/
├── listener.c          # Server implementation
├── speaker.c           # Client implementation
├── Makefile           # Build configuration
├── libft/             # Custom C library
└── ft_printf/         # Custom printf implementation

🐛 Error Handling

The program handles:

• Invalid PID
• Signal transmission failures
• Memory allocation errors
• Invalid arguments

👨‍💻 Author

Caner Çakır

• GitHub: @ccakirr

📄 License

This project is part of the 42 School curriculum.

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Made with ❤️ as part of 42 Istanbul