p1
    OpenVMS usage:buffer
    type:         vector byte (unsigned)
    access:       read only
    mechanism:    (Alpha and I64) by 32- or 64-bit reference
                  (VAX) by 32-bit reference
    The address of the buffer containing the data to be transmitted.
    The length of this buffer is specified by the p2 argument.
 p2
    OpenVMS usage:buffer_length
    type:         quadword unsigned (Alpha and I64); longword
                  unsigned (VAX)
    access:       read only
    mechanism:    (Alpha and I64) by 64-bit value
                  (VAX) by 32-bit value
    The length (in bytes) of the buffer containing data to be
    transmitted. The address of this buffer is specified by the p1
    argument.
 p3
    OpenVMS usage:socket_name
    type:         vector byte (unsigned)
    access:       read only
    mechanism:    by item_list_2 descriptor
    The remote port number and IP address of the message destination.
    The p3 argument is the address of an item_list_2 descriptor
    pointing to the socket address structure containing the remote
    port number and IP address.
 p4
    OpenVMS usage:mask_longword
    type:         longword (unsigned)
    access:       read only
    mechanism:    by value
    Longword of flags to specify attributes for this write operation.
    The following table lists the available write flags:
    Write Flag            Description
    TCPIP$C_MSG_OOB       Writes an out-of-band (OOB) byte.
    TCPIP$C_MSG_          Sends message directly without routing.
    DONTROUTE
    TCPIP$C_MSG_NBIO      Completes the I/O operation and returns
                          an error if a condition arises that would
                          cause the I/O operation to be blocked.
                          (Similar to using IO$M_NOWAIT.)
 p5
    OpenVMS usage:buffer_list
    type:         vector byte (unsigned)
    access:       read only
    mechanism:    (Alpha and I64) by 32- or 64-bit
                  descriptor-fixed-length descriptor
                  (VAX) by 32-bit descriptor-fixed-length descriptor
    Input buffer list describing one or more buffers containing
    the data to be transmitted. The p5 argument is the address
    of a descriptor pointing to a input buffer list. Buffers are
    transmitted in the order specified by the input buffer list. The
    transfer-length value returned in the I/O status block is the
    total number of bytes transferred from all buffers.
    If you use the p1 and p2 arguments, do not use the p5 argument;
    they are mutually exclusive.