Lines beginning with "S:" are server messages.
Lines beginning with "C:" are client messages.

S: <listening on port 8778>
C: <connecting>
If the client is from an allowed IP:
S: R
Or else:
S: D
S: <close connection>

From now on, we assume that a connection is already built to the server

C: L <uname> <pass>
If the client is already logged in:
S: L
If uname or pass is missing:
S: E
If the specified user is not allowed to login:
S: D
If the specified uname/pass combination is bad:
S: B
If login successful:
S: S

C: Q
S: S
S: <close connection>

C: U <uid>
If client hasn't login yet:
S: L
If uid is not numeric:
S: E
If uid is used:
S: U
If uid is free:
S:F

C: N <uname>
If client hasn't login yet:
S: L
If uname exists:
S: U
If uname doesn't exist:
S: F

C: A <uname>:<uid>:<teacher?>:<samba?>:<passwd>:<comment>
If client hasn't login yet:
S: L
If uid, teacher?, samba?, passwd or comment is not specified
S: E
If uid is not numeric:
S: E
If uid or uname is used:
S: E
If teacher? not 0 nor 1, and samba? not 0 nor 1
S: E
If tempfile or scriptfile couldn't be created:
S: F
If user couldn't be created:
S: F
If user has been created:
S: S

C: D <uname>
If client hasn't login yet:
S: L
If uname doesn't exist:
S: E
If scriptfile couldn't be created:
S: F
If user cannot be deleted:
S: F
If user is deleted:
S: S