INT 21 - TopWare Network OS v5.10+ - RECEIVE OF USER-DEFINED PACKETS            
	AX = FF9Ah
	ES:BX -> buffer for user-defined packet (see #02532)
Return: nothing


Format of TopWare user-defined packet:
Offset	Size	Description	(Table 02532)
 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