public static void main(String[] args) throws Exception {
        if (args.length != 1) {
            System.err.println(
                    "Usage: java ReliableUdpServer <listening port>");
            System.exit(1);
        }
        int serverPort = Integer.parseInt(args[0]);
        //create new datagram socket with a specific port number binded to it
        DatagramSocket dataSocket = new DatagramSocket(serverPort);

        new ReliableUdpThread(dataSocket).start();
    }