2,5.

Today I will just talk about Communication with Devices.
I'm gradually developing interest for IoT and will actually work on the projects I have always wanted to work on.

MQTT vs HTTP at a Glance

MQTT is an industry-standard IoT protocol (Message Queue Telemetry Transport). It is a publish/subscribe (pub/sub) messaging protocol.

HTTP is a "connectionless" protocol: with the HTTP bridge, devices do not maintain a connection to the cloud. Instead, they send requests and receive responses.

From Industrial IoT on Google Cloud Platform on Coursera

Delivery Guarantees
MQTT has three levels of service:

• At most once. Guarantees at least one attempt at delivery.
• At least once. Guarantees the message will be delivered at least once.
• Exactly once. Guarantees the message is delivered only once.

MQTT also has:

• Last will and testament. If a client (ie device) is disconnected unexpectedly, the subscribers will be notified by the MQTT broker.
• Retained messages. New subscribers will get an immediate status update.

The ride is getting more interesting for me!

Protocols - GoogleCloud