Format of SPX header:
Offset	Size	Description	)
 00h	WORD	(big-endian) checksum
 02h	WORD	(big-endian) length in bytes of total packet
 04h	BYTE	transport control
 05h	BYTE	packet type (see #03816 at INT 7A/BX=0003h)
 06h 10 BYTEs	destination internet address
 10h	WORD	(big-endian) destination socket
 12h 10 BYTEs	source internet address
 1Ch	WORD	(big-endian) source socket
 1Eh	BYTE	connection control (see #03827)
 1Fh	BYTE	datastream type
		FEh terminate connection request packet
		FFh terminate connection acknowledgement packet
		other user-defined, ignored by SPX
 20h	WORD	(big-endian) source connection ID
 22h	WORD	(big-endian) destination connection ID
 24h	WORD	(big-endian) sequence number
 26h	WORD	(big-endian) acknowledge number
 28h	WORD	(big-endian) allocation number
SeeAlso: #03815