Problem with a UDPSocket

UDPSockets seem not to work when ports on your router are closed. Well, I’m doing everything as the guides say but I just never get the response. It’s not a problem with my network: the program on C++ of the same type connects and recieves data just fine; to the same server, to the same port. Example project (containing the server IP and port I need to connect):
P.S. You can connect to a server just once a minute or so (since it’s an Remote Control protocol).
P.P.S. After these three bytes, server should respond with something - it doesn’t matter what is it. I just never get its response.
Am I doing something wrong?