Microsoft say this about Winsock error 10058 - WSAESHUTDOWN:

A request to send or receive data was disallowed because the socket had already been shut down in that direction with a previous shutdown call. By calling shutdown a partial close of a socket is requested, which is a signal that sending or receiving, or both have been discontinued.

Full details of Winsock TCP error 10058 - WSAESHUTDOWN:

Berkeley description: A request to send data was disallowed because the socket had already been shut down with a previous shutdown() call.

WinSock description: Same as Berkeley. By calling shutdown() you do a partial close of a socket, which means you have discontinued sending. The WinSock implementation will not allow you to send after this.

TCP/IP scenario: Calling with how=1 or how=2 sends a TCP FIN packet to the remote address, which literally means "I'm done sending." If the local host sent any more data after that point, it would be in clear violation of the TCP specification (RFCs 793 and 1122).