Java Examples - Check port

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Problem Description:

How to check whether a port is being used or not?

Solution:

Following example shows how to check whether any port is being used as a server or not by creating a socket object.

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

public class Main {
   public static void main(String[] args) {
      Socket Skt;
      String host = "localhost";
      if (args.length gt; 0) {
         host = args[0];
      }
      for (int i = 0; i < 1024; i++) {
         try {
            System.out.println("Looking for "+ i);
            Skt = new Socket(host, i);
            System.out.println("There is a server on port "
            + i + " of " + host);
         }
         catch (UnknownHostException e) {
            System.out.println("Exception occured"+ e);
            break;
         }
         catch (IOException e) {
         }
      }
   }
}

Result:

The above code sample will produce the following result.

Looking for 0
Looking for 1
Looking for 2
Looking for 3
Looking for 4. . . 


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