I wrote a simple server emulator for UO, I followed your protocol guide but I am seeing strange results. Now I will admit I am not very good with networking.
I attempted to login with clients 2.0.3 and 4.0.11c with removed encryption, I get same results with both.

Here is the Post Login Packet

Hex:
C0A82208063656E747269667567616C000000000000000000070617373776F72640000000000000000000000FF
Ascii:
??☻ ?centrifugal password

So according to this the ID would be C0 and not 91

I know I am doing something wrong, so can someone help me figure out why I get strange results?