OPC UA MODBUS PLC Emulator

A complete OPC UA server emulator that simulates a MODBUS PLC connection, along with a scanner client for testing and monitoring. Built with Python using the asyncua library and fully containerized with Docker.

Features

OPC UA Server (PLC Emulator)

• Temperature Sensors: 10 sensors with realistic temperature variations (20-40°C)
• Pressure Sensors: 10 sensors with pressure readings (1000-2000 units)
• Flow Meters: 10 flow meters with flow rate data (20-80 L/min)
• Motor Controls: 10 digital motor on/off controls
• Discrete Inputs: 20 limit switches and digital inputs
• Setpoints: 10 configurable setpoint values
• System Status: PLC running status, communication health, error counters
• OPC UA Methods: Remote PLC restart functionality

OPC UA Scanner/Client

• Full Node Discovery: Automatically discovers all server nodes
• Real-time Monitoring: Continuous monitoring of selected variables
• Method Invocation: Can call server methods remotely
• Structured Output: Organizes discovered nodes by type
• JSON Export: Saves scan results for analysis

Quick Start

Prerequisites

• Docker and Docker Compose
• Make (optional, for convenience commands)

1. Clone and Setup

# Create project directory
mkdir opcua-modbus-emulator
cd opcua-modbus-emulator

# Create all the files (copy the code from the artifacts above)
# Files needed:
# - opcua_server.py
# - opcua_scanner.py
# - docker-compose.yml
# - Dockerfile.server
# - Dockerfile.scanner
# - requirements.txt
# - Makefile (optional)

2. Build and Start

# Using Make (recommended)
make build
make up

# Or using Docker Compose directly
docker-compose build
docker-compose up -d opcua-server

3. Test the Scanner

# Run scanner once
make scan

# Or with Docker Compose
docker-compose run --rm opcua-scanner

4. Monitor Continuously

# Start continuous monitoring
make monitor

# Or manually
docker-compose run --rm opcua-scanner python opcua_scanner.py

Usage

Available Make Commands

make help      # Show all available commands
make build     # Build Docker images
make up        # Start the server and scanner
make down      # Stop all services
make scan      # Run scanner once
make monitor   # Start continuous monitoring
make logs      # Show logs
make status    # Check service status
make clean     # Clean up containers
make test      # Test server connectivity
make info      # Show server information

Manual Docker Commands

# Start server and scanner
docker-compose up -d opcua-server opcua-scanner

# Run scanner interactively
docker-compose run --rm opcua-scanner

# View logs
docker-compose logs -f opcua-server
docker-compose logs -f opcua-scanner

# Stop everything
docker-compose down

Server Configuration

Connection Details

• Server URL: opc.tcp://localhost:4840/freeopcua/server/
• Port: 4840
• Namespace: http://examples.freeopcua.github.io

Node Structure

PLC_System/
├── Temperature_Sensors/
│   ├── Temperature_Sensor_00 (Double, °C)
│   ├── Temperature_Sensor_01 (Double, °C)
│   └── ... (10 total)
├── Pressure_Sensors/
│   ├── Pressure_Sensor_00 (Double, units)
│   ├── Pressure_Sensor_01 (Double, units)
│   └── ... (10 total)
├── Flow_Meters/
│   ├── Flow_Meter_00 (Double, L/min)
│   ├── Flow_Meter_01 (Double, L/min)
│   └── ... (10 total)
├── Motor_Controls/
│   ├── Motor_00_Running (Boolean)
│   ├── Motor_01_Running (Boolean)
│   └── ... (10 total)
├── Discrete_Inputs/
│   ├── Limit_Switch_00 (Boolean)
│   ├── Limit_Switch_01 (Boolean)
│   └── ... (20 total)
├── Setpoints/
│   ├── Setpoint_00 (Double)
│   ├── Setpoint_01 (Double)
│   └── ... (10 total)
├── System_Status/
│   ├── PLC_Running (Boolean)
│   ├── Communication_OK (Boolean)
│   ├── Last_Update (DateTime)
│   └── Error_Count (UInt32)
└── Methods/
    └── RestartPLC (Method)

Data Simulation

The emulator generates realistic MODBUS PLC data:

• Temperature: Base temperatures 20-40°C with ±2.5°C variation
• Pressure: Base pressures 1000-2000 units with ±25 unit variation
• Flow: Flow rates 20-80 L/min with realistic fluctuations
• Motors: Random on/off states with persistence
• Discrete Inputs: Occasional state changes (limit switches)
• Communication: Simulated 1% communication error rate

Monitoring Output Example

============================================================
MONITORING UPDATE - 2024-01-15 10:30:45
============================================================
Temperature_Sensor_00: 22.35
Temperature_Sensor_01: 24.12
Pressure_Sensor_00: 1045.2
Flow_Meter_00: 67.89
Motor_00_Running: True
PLC_Running: True
Communication_OK: True
Error_Count: 2

Use Cases

Industrial Automation Testing

• Test HMI/SCADA systems
• Validate OPC UA client applications
• Simulate factory floor equipment

Development & Training

• Learn OPC UA protocol
• Develop industrial IoT applications
• Test data acquisition systems

Integration Testing

• Validate communication protocols
• Test system integration
• Simulate equipment failures

Security Notes

• The emulator runs with non-root users in containers
• No authentication is configured (suitable for testing only)
• For production use, implement proper OPC UA security

Troubleshooting

Common Issues

1. Port 4840 already in use

   # Check what's using the port
   lsof -i :4840
   # Kill the process or change port in docker-compose.yml

2. Scanner can't connect

   # Check if server is running
   make status
   # Check server logs
   make server-logs

3. Permission denied

   # Fix permissions
   sudo chown -R $USER:$USER ./logs ./scan_results

Logs Location

• Server logs: ./logs/
• Scan results: ./scan_results/scan_results.json

Dependencies

• Python 3.11+
• asyncua 1.0.6
• cryptography 41.0.7
• Docker & Docker Compose

License

This project is provided as-is for educational and testing purposes.

Contributing

Feel free to submit issues and enhancement requests!