Subscribe/Unsubscribe Path

Subscribe

The subscribe/suback sequence shows the potential for a publish publish for the newly subscribed topic before the suback packet arrives.

Client -> Haka: subscribe call note right: subscribe(topic=T) packet enqueued. Client <- Haka: subscribe return == ... == Client -> Haka: write call Haka -> Socket: send subscribe note right: subscribe packet transferred to socket write buffer. Client <- Haka: write return == ... == Client -> Haka: read call Haka <- Socket: recv publish(topic=T, QoS=0) note right: publish(topic=T) may arrive before suback! Client <- Haka: on_publish call Client -> Haka: on_publish return Client <- Haka: read return == ... == Client -> Haka: read call Haka <- Socket: recv suback(topic=T) Client <- Haka: on_suback call Client -> Haka: on_suback return Client <- Haka: read return

Unsubscribe Path

The unsubscribe/unsuback sequence is very similar to the subscribe/suback sequence.

Client -> Haka: unsubscribe call note right: unsubscribe packet enqueued. Client <- Haka: unsubscribe return == ... == Client -> Haka: write call Haka -> Socket: send unsubscribe note right: unsubscribe packet transferred to socket write buffer. Client <- Haka: write return == ... == Client -> Haka: read call Haka <- Socket: recv unsuback Client <- Haka: on_unsuback call Client -> Haka: on_unsuback return Client <- Haka: read return