What causes the ENOTCONN error?

Question

I\'m currently maintaining some web server software and I need to perform a lot of I/O operations. The read(), write(), close() and

Answer 1

If you're sure you've connected properly in the first place, ENOTCONN is most likely to be caused by either the fd being closed on your end (perhaps in another thread?) while you're in the middle of a request, or by the connection dropping while you're in the middle of the request.

In any case, it means that the socket is not connected. Go ahead and clean up that socket. It's dead. No problem calling close() or shutdown() on it.