I don't think you can change the port number through any configuration at this stage. But if you are compiling OpenModelica compiler (omc) from sources then you can easily change the port number

refer to the source code  under OMCompiler/SimulationRuntime/opc/ua

client.c:141:                                           "opc.tcp://localhost:4841");
omc_opc_ua.c:458:                         state->nl = UA_ServerNetworkLayerTCP(UA_ConnectionConfig_standard, 4841);


you can change the above two lines in corresponding lines and recompile your omc.

Hope this helps.

thank you @ravi. Although I dont have previous experience in compiling omc, I will look into and try out the method you've suggested. I'll update once I get some lead

Best,
Jal

Alright so I now have an update!

1. First, it was the problem with the port number 4841. At that point I was using Movicon NeXT annd after having a chat with Movicon we figured it was something to do with their software. OPC-UA in that software is still in beta version or not fully developed. I then shifted to Ignition software and it has been working fine with that



2. And I was successfully able to change the OPC-UA port from the documents youv've mentioned and re build the omc. It worked! I was able to Start an OPC-UA srever from a Modelica code using omc at my new server port.