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

 efn
    OpenVMS usage:ef_number
    type:         longword (unsigned)
    access:       read only
    mechanism:    by value
    Event flag that $QIO sets when the I/O operation completes. The
    efn argument is a longword value containing the number of the
    event flag, however, $QIO uses only the low-order byte.
    If efn is not specified, event flag 0 is set.
    The specified event flag is set if the service terminates without
    queuing an I/O request.
 chan
    OpenVMS usage:channel
    type:         word (unsigned)
    access:       read only
    mechanism:    by value
    I/O channel that is assigned to the device to which the request
    is directed. The chan argument is a word value containing the
    number of the I/O channel.
 func
    OpenVMS usage:function_code
    type:         longword (unsigned)
    access:       read only
    mechanism:    by value
    Function codes and function modifiers specifying the operation
    to be performed. The func argument is a longword containing the
    function code.
    For information about the network pseudodevice and TELNET device
    function codes and modifiers, see Network Pseudodevice Driver
    Functions and <REFERENCE>(TEL_FUNC_CODE).
 iosb
    OpenVMS usage:io_status_block
    type:         quadword (unsigned)
    access:       write only
    mechanism:    by 32-bit reference or 64-bit reference (Alpha)
                  by 32-bit reference (VAX)
    I/O status block to receive the final completion status of the
    I/O operation. The iosb is the address of the quadword I/O status
    block.
    When the $QIO begins executing, it clears the event flag. The
    $QIO also clears the quadword I/O status block if the iosb
    argument is specified.
    Although the iosb argument is optional, Compaq strongly
    recommends that you specify it, for the following reasons:
    o  If you are using an event flag to signal the completion of
       the service, you can test the I/O status block for a condition
       value to be sure that the event flag was not set by an event
       other than service completion.
    o  If you are using the $SYNCH service to synchronize completion
       of the service, the I/O status block is a required argument
       for $SYNCH.
    o  The condition value returned in R0 and the condition value
       returned in the I/O status block provide information about
       different aspects of the call to the $QIO service. The
       condition value returned in R0 provides information about the
       success or failure of the service call itself; the condition
       values returned in the I/O status block give information on
       the success or failure of the service operation. Therefore,
       to access the success or failure of the $QIO call, check the
       condition values returned in both the R0 and the I/O status
       block.
 astadr
    OpenVMS usage:ast_procedure
    type:         procedure value
    access:       call without stack unwinding
    mechanism:    by 32- or 64-bit reference (Alpha)
                  by 32-bit reference (VAX)
    AST service routine to be executed when the I/O completes. The
    astadr argument is the address of the AST routine.
    The AST routine executes at the access mode of the caller of
    $QIO.
 astprm
    OpenVMS usage:user_arg
    type:         quadword unsigned (Alpha); longword unsigned (VAX)
    access:       read only
    mechanism:    by 32- or 64-bit value (Alpha)
                  by 32-bit value (VAX)
    AST parameter to be passed to the AST service routine. On Alpha
    systems, the astprm argument is a quadword value containing the
    AST parameter. On VAX systems, the astprm argument is a longword
    value containing the AST parameter.
 p1 to p6
    OpenVMS usage:varying_arg
    type:         quadword unsigned (Alpha); longword unsigned (VAX)
    access:       read only
    mechanism:    by 32- or 64-bit reference or by 64-bit value
                  depending on the I/O function (Alpha)
                  by 32-bit reference or by 32-bit value depending on
                  the I/O function (VAX)
    Optional device- and function-specific I/O request arguments. The
    parameter values contained in these arguments vary according to
    the function for which they are used. See Network Pseudodevice
    Driver I/O Functions for descriptions of the network pseudodevice
    driver I/O function codes; see List Codes for the p5 Item through
    Service Type Codes for related TELNET device driver I/O function
    codes.