The point is, that my problem doesn't affect only a special programme, but all multiplayer programmes I have access to including the official conitec sample.

@community

If you have A7.84, could you please do a quick test on your pc with the pong_multiplayer.c in the samples folder. Please test with the command line command -sv -cl and -cl (you can do the test with both server and client on the same pc) whether the sample works for you or not.