VMS Help TCPIP Services, Programming Interfaces, Sockets API, sendmsg(), Errors  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    ENOTSOCK           The socket descriptor is invalid.
    EFAULT             An invalid user space address is specified for
                       a argument.
    EMSGSIZE           The socket requires that messages be sent
                       atomically, but the size of the message to be
                       sent makes this impossible.
    EWOULDBLOCK        Blocks if the system does not have enough
                       space for buffering the user data.