The code made the assumption that a session state can be identified by
the unique session ID. However, when multiple identities from the same
device are involved, there are two sessions with the same ID running on
the device.
Hence, a second identifying criteria has to be used to uniquely identify
the correct session. Here, the ID of the group was chosen.
Unfortunately, the session state can not be cached easily anymore
leading to a small performance penalty when getting all messages for the
UI.
This Introduction BSP Client uses its own group to communicate with
existing contacts. It uses four types of messages to facilitate
introductions: the introduction, the response, the ack and the abort.
The protocol logic is encapsulated in two protocol engines, one for the
introducer and one for the introducee. The introduction client keeps the
local state for each engine, hands messages over to the engines and
processes the result and state changes they return.
