title: How to check ip is available in network or not?
body: <p>I have an list of IP which I am getting using UDP broadcasting,
  so on the bases of Alive/Death packet ,i got to know whether user alive or went off.</p>
  
  <p>But i have an single case suppose user went out from network before sent death packet,
  then how can I detect user live or not.</p>
  
  <p><strong>- Solution which i have:</strong></p>
  
  <p>So for this purpose I m running an thread ,in which i send an dummy data to all user(from ip list), so if any ip is not available then it respond IO exception.
  but it taking to much time to identify ip in network.</p>
  
  <p>pls suggest me if have any faster solution.</p>