To destruct TCP connections gracefully base on fatal signals does not seem to be a good idea.

I would suggest to put this in the hands of the peer. Between two nodes that have TCP connections, and want to maintain it all the time, it is better to have heart beat sending back and forth, or at least one way (depends on your application). When the heartbeats is gone (not received for a while, or couple retries), the connection should be deemed as gone, then both sides should try to reestablish the connection.

Generally speaking heartbeats should be handled on its own thread, so it is not blocked by anyone else.

The other thing is that, you should look into your code, see whether there is any blocking call in your socket program. If you can, try to avoid them, so you always have the chance to check the connection.