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

    EBADF              The fildes argument is not a valid open file
                       descriptor.
    EINTR              A signal was caught during the ioctl()
                       operation.
    If an underlying device driver detects an error, errno might be
    set to one of the following values:
    EINVAL             Either the request or the arg argument is not
                       valid.
    ENOTTY             Reserved for Compaq use. The fildes argument
                       is not associated with a character special
                       device, or the specified request does not
                       apply to the type of object that the fildes
                       argument references.
    ENXIO              The request and arg arguments are valid for
                       this device driver, but the service requested
                       cannot be performed on the particular
                       subdevice.