Detecting a closed connection

Hello,

in a client/server system running on base of Event, I check for closed
connections and remove all related data from the server process, inform
other related clients and so on. This is done via an io read/error event
watcher. The callback calls a function that first of all checks the
handle/socket by fileno(). Quite simple, but it works perfectly if a
client dies a usual way, e.g. by signal.

Now, it does NOT work if the client system is shut down by switching off
its hardware. The server system does not recognize this (remote shells
do not close etc.) So, there seems to be no catchable event. Are there
known strategies to detect such cases?

Thanks in advance

                        Jochen