Solaris

Port activity isn't logged, that would be overkill. You might have a look at the system logs (dmesg) for error events, but I doubt it is really system related. You should connect your application to a debugger and see what happens to your listening socket.

If the server is actually still listening, a pstack run against it should show a thread blocked in accept().

IME the most likely cause is a thread calling close() on the wrong file descriptor and killing the socket. You can run truss against the server and watch for that.

And are you checking the value that you get from accept() to make sure it's not an error? And when you do get an error, do you log it somewhere?

Because if the socket gets closed out from under accept(), it should return with an error.

Thanks. The thread is not available in the pstack dump. Unfortunately, we didn't log anything in the catch block(error condition case).

Is there any Solaris logs where I can get the reason about the port in LISTEN state which got killed or closed?

Why not starting by correcting this issue first ?
No.