Web socket event when reachable again

I wonder if a lamp which was powered off - and therefore unreachable - does send a message (via Zigbee) to deConz so it knows it is reachable again. If it does, it would be great to have a web socket event notifying my application (which is listening on the web socket) about that state change (reachable: true). Currently I do not see any events from any lamp at all. So, maybe it is my fault. If so, than please ignore this feature request and I would appreciate any hint on what I do wrong.
best regards, Peter