Here is a simple port  scanner that scan  all ports:

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

public class ScanPort {   

 public static void main(String args[]) {        
  for (int portNumber = 0; portNumber < 65536; portNumber++) {           
try {                
   System.out.println("checking for port " + portNumber + " availability"); 

   /*create a ServerSocket */
 ServerSocket serverSocket = new ServerSocket(portNumber);

/*Available portNumbers*/
 System.out.println("checking for port " + portNumber + " availability, succeeded");

 /*if port number is occupied an IOException will be throwen*/ 
catch (IOException x) {               
System.out.println("ERROR MESSAGE: checking for port " + portNumber + 
   " availability, failed");            
                   }        
           }         
   }
}