1:
C->H: GUID xxx
H->C: ACCP
C->H: DESC xxx
H->C: WELC

2:
C->H: DESC xxx
H->C: ACCP
C->H: GUID xxx
H->C: WELC

3:
C->H: GUID xxx1
H->C: ACCP
C->H: GUID xxx2
H->C: ACCP
C->H: GUID xxx3 (note that this will be the authoritative one)
H->C: ACCP
C->H: DESC xxx
H->C: WELC

but this remains a state machine (even a very simple one):

Node:
S0 : initial state
S1: state when GUID was received first
S2: state when DESC was received first
S3: end state (welc)

"Function meaning":
Sx (Y) = Sz means when state is Sx and Y is received, go to Sz.

S0 (GUID) = S1  [accp sent]
S1 (GUID) = S1 [accp sent]
S1 (DESC) = S3 [welc sent]

S0 (DESC) = S2  [accp sent]
S2 (DESC) = S2 [accp sent]
S2 (GUID) = S3 [welc sent]


Can you give an example with a password. I'd like to know at which time you reject invalid login and/or invalid password.

Eric