The clnt_destroy routine destroys the client's RPC handle by
    deallocating all memory related to the handle. The client is
    undefined after the clnt_destroy call.

    If the clnt_create routine had previously opened the socket
    associated with the client handle or the program had used the
    clnt_control routine to set CL_FD_CLOSE, this routine closes the
    socket. If the clnt_create routine had not previously opened the
    socket associated with the client handle or the program had used
    the clnt_control routine to set CL_FD_NCLOSE, this routine leaves
    the socket open.