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!
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