Adds a handler for one event type (EVENT.*), or * for every event.
One poll: acknowledges what was handled since the last, handles what arrives. Answers whether more is waiting. A call while a poll is in flight joins it rather than starting a second one: two overlapping polls are both handed every SET not yet acknowledged, and would handle each twice.
Finds the transmitter and the stream, then polls until stop().
Stops polling. Acknowledgements not yet sent are sent by the next start's first poll.
Remembers a local session's person and identity provider session, after a sign-in.
OptionalexpiresAt: DateForgets a local session, after a sign-out.
Asks the transmitter to send a verification event (SSF 1.0 section 8.1.4.2), to prove the stream end to end.
Optionalstate: string
The stream the receiver is polling, once started.