@startuml Seq_Subscription

title Real-time Data Transfer — Subscription

participant "CloudConnectController" as CC
participant "MqttClient" as MQTT
participant "AWS IoT Core (MQTT broker)" as AWS

== Subscribe (on every new session) ==

MQTT -> CC : didStateChanged(Connected)\n→ onCloudStateChanged()
CC -> MQTT : subscribe(topic, QoS)
MQTT -> AWS : SUBSCRIBE (topic filter, requested QoS)
AWS --> MQTT : SUBACK

== Subscription Delivery ==

AWS -> MQTT : PUBLISH on the subscribed topic
MQTT -> CC : didMessageReceived(payload, topic)\n→ onCloudMessageReceived()
CC -> CC : parse Envelope → Header\n(msgId, sequence, timestamp)
CC -> CC : convert serialized Protobuf payload → JSON for output

@enduml