Hello,
I am using Codesys V3.5 SP18 Patch 18.
I am trying to make OpcUa Server/Client on two PLCs. Configured the server normally and read all variables from server using UA Expert.
But when starting client on Codesys trough datasource i got error 7001.
Communication failure in data sources OPC UA library. Exact error was not specified.
Does anybody have idea what problem could be?

Hello,
I have a similar problem.
I have 30 PLCs Raspberry Pi (V4.5.0.0) which are running OpcUA Server.
My OpcUA Client runs on windows pc (CodeSys Control win64 V3.5.18.20).
My problem is that the Client cannot be connected too more than 10 Servers at the same time.
The Servers that failed to be connect have the error message:
Communication failure in data sources OPC UA library. Exact error was not specified. Error ID 7001.
All Servers are Tested and communicate well with the client if are not exceed the number of 10 at the same time!!

There is a hard-coded limit of ten TLSContexts in the runtime. So if you don't use encryption, you should be able to connect to a few more, maybe 60?

If you need more, well its convincing CODESYS that you need more and have them to change the magic number in a future release.