Example 11-1: Look for Local Ports

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//

ServerSocket server = new ServerSocket(port);

}

catch (IOException e) {

System.out.println("There is a server on port

" + port + ".");

} // end try

} // end for

}

}

Here's the output I got when running

LocalPortScanner on my NT workstation:

D:JAVAJNP2examples11>java LocalPortScanner

There is a server on port 135.

There is a server on port 1025.

There is a server on port 1026.

There is a server on port 1027.

There is a server on port 1028.