@green@mk.absturztau.be Ah, you could be in a TIME_WAIT state. Just wait a bit, or add some extra fluff: (socket.create_server() does this automatically on POSIX platforms according to the docs)Running an example several times with too small delay between executions, could lead to this error: OSError: [Errno 98] Address already in use This is because the previous execution has left the socket in a TIME_WAIT state, and can’t be immediately reused. There is a socket flag to set, in order to prevent this, socket.SO_REUSEADDR: s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) s.bind((HOST, PORT)) the SO_REUSEADDR flag tells the kernel to reuse a local socket in TIME_WAIT state, without waiting for its natural timeout to expire.