When calling ocpp15ConnectionToCSMS, a client and a server are created. The issue is that in these two cases clientPath is not used the same way. In the client, it is used to build the from header following "$clientPath:$clientPort". Whereas in the server it is used as a path. So to call the server, this route is expected: "localhost:$clientPort/$clientPath.removeSuffix("/")
Two parameters should be used in the lib to make a difference. Otherwise we cannot use ocpp15ConnectionToCSMS as client and server at the same time.
It may be the same issue for 16 and 20