Java Tutorial/Network/Port

High Port Scanner

   <source lang="java">

import java.net.InetAddress; import java.net.Socket; public class MainClass {

 public static void main(String[] args) {
   String host = "localhost";
   try {
     InetAddress theAddress = InetAddress.getByName(host);
     for (int i = 1024; i < 65536; i++) {
       Socket theSocket = new Socket(theAddress, i);
       System.out.println("There is a server on port " + i + " of " + host);
     }
   } catch (Exception ex) {
     System.err.println(ex);
   }
 }

}</source>

Local Port Scanner

   <source lang="java">

import java.io.IOException; import java.net.ServerSocket; public class MainClass {

 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
       ServerSocket server = new ServerSocket(port);
     } catch (IOException ex) {
       System.out.println("There is a server on port " + port + ".");
     }
   }
 }

}</source>

Low Port Scanner

   <source lang="java">

import java.io.IOException; import java.net.Socket; import java.net.UnknownHostException; public class MainClass {

 public static void main(String[] args) {
   String host = "localhost";
   for (int i = 1; i < 1024; 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) {
     }
   }
 }

}</source>

Port Scanner

   <source lang="java">

import java.net.InetAddress; import java.net.Socket; public class MainClass {

 public static void main(String[] args) {
   String host = "localhost";
   try {
     InetAddress theAddress = InetAddress.getByName(host);
     for (int i = 1; i < 65536; i++) {
       Socket connection = null;
       connection = new Socket(host, i);
       System.out.println("There is a server on port " + i + " of " + host);
       if (connection != null)
         connection.close();
     } // end for
   } catch (Exception ex) {
     System.err.println(ex);
   }
 }

}</source>

UDP Port Scanner

   <source lang="java">

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 + ".");
     }
   }
 }

}</source>