Integration test using server and client

Hello,

I need to create a server client on gitlab in integration test to check message communication between them.
Is it possible to do that?

I just try to generate a server on localhost on specific address and try to run the client, I get that error:

OSError: Multiple exceptions: [Errno 111] Connect call failed ('127.0.0.1', 8765), [Errno 99] Cannot assign requested address