How to override advertised endpoint URL for OPC UA server in Docker to connect to clients (MATLAB) on host?

[Aditi250199]

I am encountering a persistent issue when trying to connect MATLAB to a Python-based OPC UA server running inside a Docker container on my Windows 11 machine. Below are the key details:

System and Software Details
• Host OS: Windows 11 Version 24H2
• Docker Version: 28.0.4
• Python Version (inside Docker): 3.11.13
• python-opcua Package: 0.98.13
• MATLAB Version: R2024b

Setup Summary
• I have a Python OPC UA server running in a Docker container using python-opcua.
• The server is bound to opc.tcp://0.0.0.0:4840 inside the container.
• From the host machine, I try to connect MATLAB using:

uaClient = opcua('opc.tcp://:4840'); OR
uaClient = opcua('opc.tcp://localhost:4840'); OR
uaClient = opcua('opc.tcp://host.docker.internal:4840');
connect(uaClient);

• MATLAB throws the following error:
Error using opcua (line 46)
Unable to receive endpoint from URL opc.tcp://0.0.0.0:4840. Check if hostname can be resolved or try providing the IP address instead of hostname. For more information, see Troubleshooting.
• I tried connecting to my server running inside docker container using UA Expert by manually add endpoint URL (ie using Advanced add url: opc.tcp://host.docker.internal:4840/) .The UA client on host connects and the nodes of the server are read.
However, in the logs the detected endpoint is 172.17.x.x .

Troubleshooting Done

1. The Python OPC UA server is definitely running and accepting connections inside Docker (it logs the values and runs without crashing).
2. I’ve tried these endpoint settings on the server:

o opc.tcp://0.0.0.0:4840

o Setting application URI and discovery URLs as:
server.set_application_uri("opc.tcp://host.docker.internal:4840")
server.set_discovery_urls(["opc.tcp://host.docker.internal:4840"])

o Binding to host.docker.internal, localhost, and specific IPs : all fail.

3. Tried switching between host.docker.internal, localhost, and actual IPs on MATLAB’s client : all result in failure.
4. Confirmed Docker is exposing port 4840.
5. The Server.py in docker (url="opc.tcp://0.0.0.0:4840") is able to connect to a dummy client.py on host (url = "opc.tcp://localhost:4840") and UA EXPERT as client on host (url = "opc.tcp://localhost:4840").

The communication incompatibility issue arises only when MATLAB is a client on host machine.

How can I correctly override the advertised endpoint URLs returned in GetEndpoints, so they show host.docker.internal instead of 0.0.0.0?
Is there a clean way to bind and advertise different endpoint addresses using python-opcua?

I’d appreciate any help in resolving this. Thank You.

[AndreasHeine]

set propper hostename of your docker container and server the same!?