INT 7F - Alloy NTNX, MW386 - SEND DATAGRAM
        AH = 11h
        DX:SI -> request block (see below)
Return: AL = status (see below)
Note:   if wildcard channel FFh used, actual channel number will be filled in
SeeAlso: AH=12h

Values for status:
 00h    successful
 01h    busy
 02h    channel range error (not 00h-3Fh)
 03h    invalid subfunction
 0Ah    packet too large (or <2 bytes if NTNX)
 0Bh    can't send packet to itself
 0Ch    invalid number of destinations
 0Dh    destination channel number out of range
 0Eh    destination user is busy
 0Fh    destination user has locked channel
 10h    channel not open
 11h    no datagram server on destination (NTNX)

Format of request block:
Offset  Size    Description
 00h    DWORD   pointer to packet to send
 04h    WORD    packet size in bytes (1-4096)
 06h    BYTE    number of destinations for packet (max 1Fh)
 07h 31 BYTEs   destination user IDs (FFh = broadcast to all except sender)
 26h 31 BYTEs   destination channels (FFh = first available channel)
 45h 31 BYTEs   return destination statuses

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