SPX IDs
Connection Control
01h-08h (not used by standard SPX)
04h Negotiate size request/response (only SPX II)
08h SPX II type packet (only SPX II)
10h End of message
20h Attention
40h Acknowledgment required
80h System packet
Datastream Type
00h-FDh Client defined (standard SPX)
FCh Orderly release request
FDh Orderly release acknowledgment
FEh End of connection
FFh End of connection acknowledgment