NO OPEN PORT in Windows XP

Question

Hi all,
i try to look all the open port of my computer with socket, but neither is open!!! How is possible?
I would to look the computer connected to my LAN, and to do so i have think to look at the echo port... but neither...
the code is:
import java.net.*;
import java.io.*;
public class LowPortScanner {
  public static void main(String[] args) {
    String host = "localhost";
    if (args.length > 0) {
      host = args[0];
    for (int i = 0; i < 26; i++) {
         System.out.println("Try " +i);
      try {
        Socket s = new Socket(host, i);
        System.out.println("There is a server on port " + i + " of "
         + host);
      catch (UnknownHostException ex) {
        System.err.println(ex);
        break;
      catch (IOException ex) {
        // must not be a server on this port
    } // end for
  }  // end main
}  // end PortScannerThanks a lot
bye

Answer 1

Port does not necessarily mean Socket.
Socket is TCP. Port applies to both TCP and UDP.
And one way isReachable() works is to use ICMP which is kind of odd and doesn't really fit into TCP nor UDP.
I am not confident that either of the ports that you listed are TCP. (Could be but I don't have the documentation here to look it up.)
OSes (including current windows ones) have a command that will list the ports in use on a computer and the type of usage. You should run the appropriate command and see what it says.