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🐍 ModbusSniffer – Free Modbus RTU Analyzer with GUI (Python / PyQt6)

A lightweight and user-friendly Modbus RTU sniffer tool with a graphical interface.
Easily analyze and debug communication between PLCs, HMIs, and other Modbus RTU devices via serial ports.

GitHub release License: MIT

ModbusSniffer GUI demo

Live preview of ModbusSniffer GUI in action

🚀 Why ModbusSniffer (This Fork)?

🔍 General Highlights

  • 🧰 Sniffs raw Modbus RTU frames from serial ports (RS-485, USB)
  • 🖥️ Graphical User Interface (PyQt6) — no terminal needed
  • 📋 Frame table: Real-time view with decoded address, function code, and data
  • 🌈 Live Logging: Color-coded request–response pairs, unmatched requests highlighted
  • 🪟 Cross-platform: Windows & Linux
  • 🆓 Free & Open Source (MIT license)

🛠️ Why This Fork (What's New)

  • 💻 Modular code refactor — clear separation into modules and classes
  • 🧠 Rewritten Modbus parser (ModbusParser class) with clean structure
  • 🖥️ Fully integrated GUI (previously only CLI)
  • 🔄 All command-line functionality preserved and upgraded into the GUI

🆕 What’s New

See the full CHANGELOG.md for details.

🔧 ToDo

  • Improve GUI with:
  • Add frame filtering
  • Add posibility to set log files path

🗺️ Roadmap

  • Support for Modbus TCP
  • Custom function code decoding
  • Advanced filtering and analysis tools
  • Plugin system for extensions

📚 Documentation & Support

  • Detailed documentation will be available in the docs/ folder soon.
  • Questions or issues? Open an issue or join the Discussions.

🧪 Testing

Run tests with pytest:

pip install -e .[dev]
pytest

Coverage report: 

pytest --cov=modbus_sniffer

🤝 Contributing

Contributions are welcome!

  1. Fork the repository
  2. Create your feature branch (git checkout -b feature-name)
  3. Commit your changes (git commit -m "Add feature")
  4. Push to branch (git push origin feature-name)
  5. Open a Pull Request

After cloning the repository and setting up a virtual environment, you can install all development tools (used in CI/CD pipeline and for local testing, linting, and packaging) with:

pip install -e .[dev]
This includes formatters, linters, type checkers, test runners, and build tools.

🤝 Acknowledgments

Thanks to the original author BADAndrea for the initial ModbusSniffer implementation.
Special thanks to all contributors and the open-source community for feedback and improvements.

📜 License

This project is licensed under the MIT License — see the LICENSE file.

This project is a fork of BADAndrea ModbusSniffer
Fork maintained by niwciu with enhancements described above.

❤️ Thank you for using this version of ModbusSniffer!

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