A server socket's handle may be closed and reopen by LWIP for another connection while the application is still using it.

A server-side application starts using a server socket after the accept() callback provides it with a handle. If the connection is aborted from client-side the error() and close() callbacks are quickly invoked. If immediately another client connection is established the accept() callback is invoked and provides the same socket handle as the last time. Having in mind that usually the LWIP is started with a higher priority the application may sleep through that whole socket handle change and keep sending data designated for the first socket through the completely new socket.