Snap7 – Industrial Ethernet Communication Suite (Extended Fork)

Snap7 is an open-source, 32/64-bit multi-platform Ethernet communication suite designed for native interfacing with Siemens S7 PLCs (S7-200, S7-300, S7-400, S7-1200, and S7-1500).

This repository is an extended, community-maintained fork of the original Snap7 project by Davide Nardella. It maintains full compatibility with the core C/C++ engine while introducing modern build toolchain fixes, continuous integration, typed Python wrappers, and a desktop diagnostic HMI workbench for rapid field commissioning.

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🎯 Fork Enhancements & Additions

While preserving the zero-dependency, high-performance C/C++ core, this fork adds:

• Toolchain & Build Modernization: Cleaned MinGW-w64 Makefiles, resolved hardcoded linking paths, and fixed 64-bit integer type issues on modern Windows toolchains.
• Continuous Integration & Security: GitHub Actions workflows for automated loopback smoke tests and CodeQL static security analysis.
• Extended Python Bridge (demo/fork_bridge.py): High-level client wrapper providing typed reads/writes (REAL, INT, DINT, BOOL), dynamic SZL parsing, and automated connection management.
• Dynamic S7 Mock Server (demo/snap7_server.py): Multi-threaded local S7 server with auto-updating Data Blocks (DB1) for offline testing without physical PLC hardware.
• Modern Diagnostic Station (demo/): PySide6 (Qt) commissioning HMI featuring real-time hardware-accelerated telemetry, connection failover, and protocol event logging.

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🖥️ Diagnostic HMI & Commissioning Workbench

Located in the demo/ directory, this tool allows automation engineers and developers to test, monitor, and validate S7 communication without installing Step 7 or TIA Portal.

Key Capabilities

Capability	Description
Telemetry Dashboard	Real-time polling and visualization of process metrics and system status
High-Rate Plotting	Low-overhead, hardware-accelerated time-series graphing powered by pyqtgraph
Dynamic Failover	Automatic fallback to the built-in simulator upon communication timeout
Protocol Event Logging	Structured, timestamped communication terminal with status codes
Runtime Configuration	Persistent settings (config.ini) for Target IP, Rack, Slot, Port, and Polling Rates

Quick Start (Demo Workbench)

cd demo
pip install -r requirements.txt

• Run in Simulation Mode (No hardware required):

python scada_dashboard.py --simulate

• Run with the Dynamic Mock Server:

# Terminal 1: Start local S7 server
python snap7_server.py

# Terminal 2: Launch diagnostic client
python scada_dashboard.py

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🔌 Python Client Quick Example

The Python bridge (demo/fork_bridge.py) wraps the native library for rapid scripting:

from demo.fork_bridge import ForkClient

client = ForkClient()
client.connect("192.168.0.1", rack=0, slot=1)

# Read 100 bytes from DB1 starting at offset 0
raw_bytes = client.db_read(db_number=1, start=0, size=100)

# Typed read (e.g., REAL at offset 4)
temp_value = client.read_real(db_number=1, offset=4)
print(f"Temperature: {temp_value:.2f} °C")

client.disconnect()

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📦 Pre-built Binaries

Pre-compiled native binaries are located in the repository:

Platform	Architecture	Library Path
Windows	32-bit (x86)	release/Windows/Win32/snap7.dll
Windows	64-bit (x64)	release/Windows/Win64/snap7.dll
Linux	64-bit (x86_64)	release/Linux/x86_64/libsnap7.so
Linux	ARMv7 (RPi / Embedded)	release/Linux/arm_v7/libsnap7.so

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🔧 Building the Core C/C++ Library from Source

Prerequisites

• Linux (Debian/Ubuntu):

sudo apt-get update && sudo apt-get install build-essential

• Windows: MSYS2 with mingw-w64-x86_64-gcc and make.

Compilation

• Linux (x86_64):

cd build/unix
make -f x86_64_linux.mk

• Windows (MinGW-w64):

cd build/windows/MinGW64
make

Running Loopback Verification

cd examples/cpp/<platform>
make
./loopback_test

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📁 Repository Layout

snap7/
├── demo/                   # Extended tooling, Python bridge, and Qt diagnostic HMI
│   ├── scada_dashboard.py  # Diagnostic station main executable
│   ├── fork_bridge.py      # High-level typed Snap7 Python wrapper
│   ├── snap7_server.py     # Standalone dynamic mock server
│   ├── sensor_simulator.py # Process metric generator
│   └── ui/                 # PySide6 layout components and design tokens
├── src/                    # Core Snap7 C/C++ source code
│   ├── core/               # ISO-on-TCP and S7 protocol stack
│   ├── lib/                # API exports (snap7.def, libmain)
│   └── sys/                # OS abstraction layer (sockets, threads)
├── build/                  # Makefiles for Linux, Windows, macOS, BSD, and Solaris
├── examples/               # Native examples (C/C++, C#, Pascal, LabVIEW)
├── docs/                   # Deployment guides and network architecture notes
├── SECURITY.md             # Security policy and vulnerability disclosure
└── LICENSE                 # LGPL-3.0 License

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🔐 Industrial Deployment & Security

Deploying software directly onto OT/ICS networks requires strict operational measures:

• Restrict access to S7 TCP Port 102 using managed industrial firewalls or VLAN segmentation.
• Note that legacy S7comm is an unencrypted, unauthenticated protocol; do not route raw S7 traffic across untrusted or public networks.
• Refer to docs/secure-deployment.md for network hardening guidelines.

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📄 License

This project is licensed under the GNU Lesser General Public License v3.0 (LGPLv3).

See LICENSE and lgpl-3.0.txt for details.

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🌐 Acknowledgments

• Davide Nardella – Creator and lead developer of the foundational Snap7 library.
• The Open-Source Industrial Automation Community for testing, protocol validation, and continuous field feedback.