No subject

protocol with just TT/KK used in the inverse.

requests:
YR         (starts new session)
TT base64  (message exchange)

responses
YR base64  (first message in an exchange)
KK base64  (additional message in an exchange)
AF base64  (last message in an exchange)
BH error   (failure)

Plus a bunch of other commands, all shared between the modes

Seems like it does not matter very much which command you use for
requests (TT/KK/AF), with the exception of YR only used when starting a
new session.

Regards
Henrik