🛰️ minitalk – C Unix signals

[](LICENSE)

‍Minitalk is a 42 project that demonstrates inter-process communication (IPC) using Unix signals (SIGUSR1, SIGUSR2). The client process encodes messages bit-by-bit, while the server side acknowledges each bit to ensure reliable, synchronous data transfer.

🔗 View on GitHub 📚 View full documentation

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✨ Features

See features

• Signal-Based Communication
  Transmits data between processes using Unix signals (SIGUSR1, SIGUSR2).
• Bit-Level Message Encoding
  Converts each character of the message into binary and sends it bit-by-bit.
• Synchronous Acknowledgment System
  Ensures reliable delivery by waiting for the server to acknowledge each bit before sending the next.
• Robust Signal Handling
  Handles asynchronous signal reception with reentrant-safe functions and proper flow control.
• Custom Protocol Over Signals
  Implements a lightweight protocol to distinguish between data bits and end-of-message signals.
• Minimal Latency Transmission
  Optimized signal dispatching and response time to achieve near real-time communication.
• PID-Based Targeting
  The client can dynamically target any server process by providing its PID as an argument.

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🎬 Demo

‍Here's a quick look at how client/server communication works in Minitalk:

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⚙️ How It Works

See details

1. The server starts and prints its PID. 2. The client takes the server PID and a message as input. 3. Each character is broken down into bits and sent one bit at a time:

• SIGUSR1 represents binary 0
• SIGUSR2 represents binary 1

4. The server rebuilds characters from incoming signals. 5. The server sends an acknowledgment after each bit, allowing safe and synchronous transmission.

📡 Signal Flow – Sequence Diagram

sequenceDiagram
    participant Client
    participant Server
 
    Client->>Server: SIGUSR1 (bit = 0)
    Server-->>Client: ACK (SIGUSR1)
 
    Client->>Server: SIGUSR2 (bit = 1)
    Server-->>Client: ACK (SIGUSR1)
 
    loop For each bit
        Client->>Server: SIGUSR1 or SIGUSR2
        Server-->>Client: ACK
    end
 
    Client->>Server: End of message
    Server-->>Client: Final ACK

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🚀 Usage

See usage guide

1. To compile both executables: 🛠️

make

Note: This project uses libft as a git submodule. If you're cloning the repository for the first time, don't forget to initialize and update submodules:

git clone --recurse-submodules https://github.com/to0nsa/minitalk.git

or if you already cloned it:

git submodule update --init --recursive

2. Run the server Start the server in one terminal. It will print its Process ID (PID):

./server
PID: <PID>
Waiting for a message...

3. Run the client Use the PID from the server output to send a message:

./client <PID> "Your message here"

🔄 Expected behavior

• The server will print each received character in real time.
• The client will wait for an acknowledgment from the server after each bit to ensure safe delivery.

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🗂️ Project Structure

See project structure

libft/
├── include/         # Header file with function prototypes, librairies...
├── srcs/            # client.c / server.c /utils.c
├── libft/           # Custom C library
├── objs/            # Object files (auto-generated)
└── Makefile         # Clean, silent build system with useful targets

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📝 License

This project is licensed under the [MIT License](LICENSE).

You are free to use, modify, and distribute this code for academic, personal, or professional purposes. Attribution is appreciated but not required.

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📬 Contact

If you have any questions, suggestions, or feedback, feel free to reach out:

• 📧 Email: nicol.nosp@m.as.l.nosp@m.ovis@.nosp@m.hotm.nosp@m.ail.f.nosp@m.r
• 💻 GitHub: github.com/to0nsa

You're also welcome to open an issue or leave a comment on the repository.