OPC/UA Client Sample Project

This project demonstrates a Python implementation to interact with an OPC/UA server, enabling the reading of tag values in either standard read or subscription modes. The provided code is built using the asyncua library, which supports asynchronous communication with OPC/UA servers.

Project Overview

Features:

• Standard Read Mode: Continuously reads values from a set of nodes on the server at a specified interval.
• Subscription Mode: Listens for data changes on specific nodes and logs updates.
• Asynchronous communication ensures efficient handling of server interactions.

Prerequisites:

1. Python 3.8+ is required to run this project.
2. Install the asyncua library:

   pip install asyncua

3. Ensure access to an OPC/UA server. The server URL is specified in the code.

---

Code Walkthrough

Key Components:

• Server Connection: The client connects to the server using the Client class, with a customizable URL.

• Namespace Index: The projectName variable is used to retrieve the server's namespace index, which helps identify nodes correctly.

• Nodes to Read: Specify nodes to be read in nodesToReadStr. These are provided in the format:

  ns=<NamespaceIndex>;g=<GUID>
  

  Example:

  f"ns={idx};g=0bd2dca9-0f76-17ca-c11d-fb328f5d85b6"

• Standard Read Loop: The client reads values continuously from the specified nodes and logs the time taken for each read operation.

• Subscription Mode (Optional): The SubHandler class handles data change notifications when subscribing to a node. Uncomment the relevant section to enable this mode.

---

Usage Instructions

1. Clone the Repository:

   git clone <repository-url>
   cd <repository-folder>

2. Update Configuration:

   • Modify the url variable to point to your OPC/UA server.
   • Add or remove node strings in the nodesToReadStr list to customize which tags are read.

3. Run the Script:

   python opcua_reader.py

4. Monitor Logs: Output includes:

   • Time taken for each read operation in standard read mode.
   • Data change notifications in subscription mode (if enabled).

---

Example Output

Standard Read Mode:

INFO:root:Index of namespace OpcReadTime is 2
ReadMode time: 0:00:00.123456
Value from node ns=2;g=0bd2dca9-0f76-17ca-c11d-fb328f5d85b6: 42

Subscription Mode:

Received value for node ns=2;g=0bd2dca9-0f76-17ca-c11d-fb328f5d85b6: 42

---

Notes

• This code assumes the OPC/UA server supports GUID-based node identification.
• Ensure proper error handling and logging in production environments.
• You can adapt the read interval (asyncio.sleep) and subscription update rate as needed.

---

Future Improvements

• Add enhanced error handling and connection recovery.
• Implement dynamic node discovery to avoid manual node configuration.
• Integrate unit tests for key functions.

Happy coding! 🚀