Detecting socket disconnection?

Question

I am kinda upset that this cannot be handled in an elegant way, after trying different solutions (this, this and several others) mentioned in answers to several SO questions

Answer 1

Neither those answers applies. The first one concerns the case when the connection is broken, and the second one (mine) concerns the case where the peer closes the connection.

In a TCP connection, unless data is being sent or received, there is in principle nothing about pulling a cable that should break a connection, as TCP is deliberately designed to be robust across this sort of thing, and there is certainly nothing about it that should look to the local application like the peer closing.

The only way to detect a broken connection in TCP is to attempt to send data across it, or to interpret a read timeout as a lost connection after a suitable interval, which is an application decision.

You can also set TCP keep-alive on to enable detection of broken connections, and in some systems you can even control the timeout per socket. Not via Java however, so you are stuck with the system default, which should be two hours unless it has been modified.

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