UDP Port Scanner : Port « Network « Java Tutorial

import java.net.DatagramSocket;
import java.net.SocketException;

public class MainClass {

  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 + ".");
      }
    }
  }
}

19.10.Port
	19.10.1.	Low Port Scanner
	19.10.2.	High Port Scanner
	19.10.3.	Port Scanner
	19.10.4.	Local Port Scanner
	19.10.5.	UDP Port Scanner