Estou fazendo um programa para pingar

import java.io.*;
 import java.net.*;
 
 public class PseudoPing {
   public static void main(String args[]) {
     try {
       Socket t = new Socket(args[0], 7);
       DataInputStream dis = new DataInputStream(t.getInputStream());
       PrintStream ps = new PrintStream(t.getOutputStream());
       ps.println("Hello");
       String str = is.readLine();
       if (str.equals("Hello"))
         System.out.println("Alive!") ;
       else
         System.out.println("Dead or echo port not responding");              
       t.close();
       }
     catch (IOException e) {
       e.printStackTrace();}
       }
      }