TCP connections are not necessarily symmetric, if a read fails doesn't necessarily mean a write will fail; there is a difference between shutdown() and close()

TCP connections are not necessarily symmetric, if a read fails doesn't necessarily mean a write will fail; there is a difference between shutdown() and close() (check a packet dump or this stackoverflow question; https://stackoverflow.com/questions/11436013/writing-to-a-closed-local-tcp-socket-not-failing https://stackoverflow.com/questions/11436013/writing-to-a-cl...). The non blocking read method is fine if you wish to try to treat any client connection with a server initiated FIN as non useable (since the client will never be able to read a response from the server); it cleanly distinguishes on the client side between a CLOSE_WAIT and ESTABLISHED but with an empty read buffer.