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

    EACCES             The calling process does not have appropriate
                       permissions.
    EBADF              The descriptor is invalid.
    EDOM               The send and receive timeout values are too
                       large to fit in the timeout fields of the
                       socket structure.
    EINVAL             The optlen argument is invalid.
    EISCONN            The socket is already connected; the specified
                       option cannot be set when the socket is in the
                       connected state.
    EFAULT             The optval argument is not in a readable part
                       of the user address space.
    ENOBUFS            The system had insufficient resources to
                       complete the call.
    ENOPROTOOPT        The option is unknown.
    ENOTSOCK           The socket descriptor is invalid.
    EFAULT             The optname argument is invalid.