2.4.2 Subscribing to Topics

In addition to publishing its data, the AVR®-IoT Development Boards are capable of subscribing to a topic. When subscribing to a topic, it will receive data from the Google Cloud whenever data is published to the cloud on the subscription topic. Subscribing to topics is desired when the receiver is interested in the information sent to the broker by other connected client devices publishing data using the subscribed topic. After sending a SUBSCRIBE packet, all the messages published on the specific topic of subscription are received by the board. As of now, the board subscribes to the ‘/devices/{deviceID}/config’ topic. This is the only topic provided by Google Cloud for subscribing using the MQTT connection.