Int 21 Fn FF9A  - Topware Network Os V5.10+ - Receive Of User-defined Pac  [N]

   AX = FF9Ah
   ES:BX -> buffer for user-defined packet (see #2220)

Return: nothing

Format of TopWare user-defined packet:
Offset Size    Description (Table 2220)
 00h   BYTE    FFh
 01h   WORD    (call) length of data field plus 3
       (ret) length of received message (0000h if none received)
 03h   BYTE    destination ID (FFh for broadcast message)
 04h   BYTE    sending station ID
 05h   BYTE    type code (11h; all other codes reserved for TopWare)
 06h  N BYTEs  received message