Mastering Industrial Automation: Creating an OPC UA Simulation Server in Python

In the dynamic landscape of industrial automation, OPC Unified Architecture (OPC UA) stands as a cornerstone, facilitating seamless and secure communication among diverse automation systems. You must have been tired of downloading trial versions(create account using professional email?) for your developments/testing. This article offers a practical walkthrough on setting up an OPC UA simulation server using Python, a language celebrated for its ease of use and powerful capabilities. Whether you're a seasoned engineer or just beginning your journey in industrial automation, this guide aims to provide valuable insights into the integration of OPC UA with Python.

Why Python for OPC UA?

Python, with its user-friendly syntax and rich ecosystem, is an excellent choice for implementing OPC UA servers. Its widespread popularity among developers and engineers alike makes it an ideal tool for rapid development and testing. The opcua library in Python simplifies the creation of OPC UA servers, allowing both novices and experienced programmers to efficiently develop and deploy simulation servers.

Step 1: Install Python and Essential Libraries

• Python Installation: For those new to Python, start by downloading and installing it from the official website, python.org. Make sure to select the option to add Python to your system's PATH during installation, enabling easy access from the command line.
• Installing OPC UA Library: Open your command line and run pip install opcua. This command uses pip, Python's package installer, to download and install the OPC UA library, which is crucial for our server setup.

Step 2: Crafting the OPC UA Server Script

• Script Overview: Our script will initialize a server instance, configure its settings, and add simulated data points (variables). You can create as many variables as you want. For the sake of simplicity, I have created two simulated variables, temperature and pressure to mimic real-world data

from opcua import Server
from random import randint
import datetime
import time


server = Server()
server.set_endpoint("opc.tcp://0.0.0.0:48040/freeopcua/server/")


uri = "https://example.org"
idx = server.register_namespace(uri)


obj = server.nodes.objects.add_object(idx, "MyObject")


temp = obj.add_variable(idx, "Temperature", 0)
pressure = obj.add_variable(idx, "Pressure", 0)


temp.set_writable()
pressure.set_writable()


server.start()
print("Server started at {}".format(server.endpoint))

try:
    while True:
        # Update the temperature and pressure with random values
        temperature = randint(20, 30)
        pres = randint(200, 300)

        print("Temperature: {} °C, Pressure: {} kPa".format(temperature, pres))

        # Set the values for the variables
        temp.set_value(temperature)
        pressure.set_value(pres)

        # Sleep for some time
        time.sleep(2)

except KeyboardInterrupt:
    print("Server shutdown")
    server.stop()        

Code Walkthrough:

• Server Initialization: Begin by creating a server object and setting its endpoint URL. This URL is how clients will connect to your server. I have specified 0.0.0.0 as it allows all I.P.s to connect to this server. I am not going to get into details of that as that is not the scope here.
• Namespace Configuration: Namespaces in OPC UA are used to create unique identifiers for nodes. We'll define a custom namespace for our variables.
• Adding Variables: We'll add simulated variables like temperature or pressure to mimic real-world data.
• Server Start: Finally, we'll start the server and enable it to accept connections.

Step 3: Navigating Through Common Setbacks

• Cryptography Library: The cryptography library is needed for secure communication. Its absence can be fixed by running pip install cryptography.
• Certificates for Secure Communication: In a production environment, secure communication is vital. If needed, setting up secure endpoints involves generating and configuring certificates. For simulation purposes, using non-secure endpoints can simplify the process.
• Resolving Permission Error on Port Binding: This common error occurs when the script doesn't have permission to use the specified port. Running your script as an administrator or switching to a higher port number (above 1024) typically resolves this issue. Try running cmd in Administrator mode if you face issues.

Step 4: Executing the Server

• Running the Script: Navigate to your script's directory in the command line and execute it with python [script_name].py(e.g. python OPCUASimulation.py). This launches your OPC UA server.
• Server Testing: To test your server, connect an OPC UA client. You should see your simulated variables and be able to interact with them as you would in a real-world scenario.

Conclusion

Setting up an OPC UA server in Python is a critical skill in industrial automation, bridging the gap between theoretical knowledge and practical application. This exercise not only enhances your understanding of OPC UA but also opens up opportunities to delve into more advanced aspects like complex data structures, security implementations, and performance optimizations in OPC UA servers.