import java.net.*;
import java.io.*;

public class LocalPortScanner {

  public static void main(String[] args) {
    
    for (int port = 1; port <= 65535; port++) {
      
      try {
        // the next line will fail and drop into the catch block if
        // there is already a server running on the port
        // make sure your firewalls are turned off as otherwise
        // you will get an error and it looks as if a port is active
        ServerSocket server = new ServerSocket(port);
      }
      catch (IOException e) {
        System.out.println("There is a server on port " + port + ".");
      } // end try
      
    } // end for

  }
  
}