This change has already been proposed in Issue 1767511, which I recently replied to. I think it is valid to send an empty datagram back to the client, and not doing so could break existing code.

Also see Issue 5824 about removing the comment about recvfrom() on Linux.

Your FileNotFoundError is caused by the client removing its receiving socket file. This would also occur if the server was trying to send a non-zero datagram.

IMO this is usually an asynchronous error that is beyond the control of the server. In the TCP case, you can get similar errors if the client disconnected (BrokenPipeError, ConnectionResetError, etc). But these “error” conditions might only be detected after the server has closed its socket, which is why you don’t always see them.