note sundialsvc4 <p> The only practical way that I have ever found to determine whether a client has crashed is to oblige the protocol between the two to periodically send a &ldquo;heartbeat&rdquo; message if there is nothing else to be sent during some mutually agreed-upon interval. &nbsp; The host should record the latest timestamp as each socket sends a message, or just a boolean flag, and use a periodic timer, say about half-again as long as the heartbeat, to check for absence of response within that time. &nbsp; Upon which the host might <em>presume</em> that the client is dead. &nbsp; You see, you really can&rsquo;t be 100% sure, AFAIK, that all of the intermediates between here-and-there are still in good working order. &nbsp; Maybe the host knows that the socket has been closed or that communication has failed, or maybe it doesn&rsquo;t. &nbsp; But if a bottle washes up on shore, even if it&rsquo;s empty, you know the sender is still out there. </p> 999744 999744