for (int port = 1024; port <= 65535; port++) { try {
// the next line will fail and drop into the catch block if
// there is already a server running on port i
DatagramSocket server = new DatagramSocket(port);
server.close();
} catch (SocketException ex) {
System.out.println("There is a server on port " + port + ".");
}
}
}
}