You cannot directly do it, and you should not. Please see my comment to the question.
If the client is disconnected, it does not simply exist for the service. Everything is triggered by the initiative of the client, not service.
The fact that you can ping the client's host
means nothing. When you can ping something, it means you communicate with some service, not client. To be successfully pinged, the host should run a server implementing the ICMP protocol:
http://en.wikipedia.org/wiki/Internet_Control_Message_Protocol[
^],
http://en.wikipedia.org/wiki/Ping_%28networking_utility%29[
^].
Instead of thinking it the direction of total technology abuse, you should rather try to find a bug which causes your connection to break prematurely and fix it. This is a general and very important approach to engineering: don't try to cover up your and other's bugs with additional constructs.
—SA