import java.net.*;

public class UDPPortScanner {

  public static void main(String[] args) {
    
    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 + ".");
      } // end try
    } // end for

  }
  
}