⚡ nanoXchange-py: FIX-Based Limit Order Book Simulator (Python)

nanoXchange-py is a FIX-style message-driven Limit Order Book simulator, purpose-built in Python for rapid experimentation, educational exploration, and pre-production prototyping. It emulates the core mechanics of a trading exchange — including matching limit/market orders with price-time priority, managing multiple tickers, and dynamically evolving order books.

This simulator provides a launchpad for the future high-performance system nanoXchange (C++), and is ideal for quantitative developers, system designers, and exchange engineers looking to sharpen their edge or build novel infrastructure.

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🎯 Project Goals

• 📈 Prototype order matching algorithms using FIX-style interfaces
• 🧠 Learn realistic exchange design patterns via Python OOP
• 🔁 Provide a stepping stone toward high-performance C++ deployments
• 🛠️ Build tools for testing HFT strategies and exchange logic

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🧩 Key Concepts & Design Patterns

• FIX Protocol Emulation: All orders are submitted, parsed, and returned using a human-readable FIX-style protocol.
• Modular OOP Architecture:
  • Exchange uses the Singleton Pattern for global state
  • Command classes follow the Command Pattern for encapsulated request handling
  • Parser handles encoding/decoding and acts as the protocol translator
• MatchEngine follows Separation of Concerns, isolating trade execution logic
• OrderBook uses heap-based priority queues for price-time management
• Clean extensibility for logging, networking, or analytics

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🛠️ Features

• ✅ FIX-style order interface (e.g. 35=D|57=O1|39=AAPL|...)
• ✅ Market and Limit order support
• ✅ Modular, extensible class-based architecture
• ✅ Matching logic based on price-time priority
• ✅ Clean separation of parsing, exchange, order book, and match engine
• ✅ Unit tests covering core command and matching components
• 🔧 Ready for integration with:
  • UDP/TCP clients and servers
  • Historical scenario replays
  • GUI / REST APIs

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🚀 Dev Workflow

git clone https://github.com/nanoXchange/nanoXchange-py.git
cd nanoXchange-py
make setup        # Create & activate virtual environment
pip install -r requirements.txt
make run          # Launch interactive CLI (TODO)

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💡 User Guide (FIX-style CLI)

Once inside the prompt, use FIX-style messages:

35=D|57=O1|39=AAPL|38=5|54=BUY|11=LIMIT|55=151.0
35=D|57=O2|39=AAPL|38=3|54=SELL|11=MARKET
35=8|39=AAPL
EXIT

• 35=D: Place order
• 35=F: Cancel order
• 35=8: Display order book

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✅ Running Tests

make test

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📌 Freezing Dependencies

make freeze
# runs: pip freeze > requirements.txt

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🛣️ Roadmap

Near-term (Python)

• FIX-based CLI with parsing + encoding
• Limit and market matching via MatchEngine
• Command-based architecture (Add, Cancel, Display)
• CI workflow + pre-commit hooks (black, ruff)
• Add structured event logger
• Add scenario replay tool (JSON/CSV)

Mid-term

• Add support for batch orders
• Add UDP networking interface
• Add trade log ingestion + replay

Long-term (C++)

• Port core engine to high-performance nanoXchange (C++)
• Connect bots and client APIs to simulation
• Simulate real market dynamics and microstructure

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🤝 Contributing

We welcome contributions from quant devs, exchange engineers, and curious hackers.

1. Fork this repo
2. Create a new feature branch
3. Submit a pull request with clear commits and passing tests

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📜 License

This project is licensed under the MIT License. See LICENSE.

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🙌 Acknowledgements

• Inspired by professional matching engine architecture
• Designed for education, experimentation, and performance evolution
• Built by:
  • Julian Tay
  • Nihal Ramesh

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📬 Contact

📧 Questions or collaboration ideas?
📂 Open an Issue
🚀 Stay tuned for the C++ version: nanoXchange