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MQTT Protocol

MQTT Protocol Tutorial

MQTT.ORG docs: a publish/subscribe messaging protocol which is extremely lightweight, for IoT, M2M and mobile messaging

_images/pubsub_concept.png

Publish/Subscribe Model

_images/pubsub_concept.png

MQTT Control Packets

MQTT Packet Structure

Compact: 1 byte header

MQTT Packet Types

MQTT Packet Flags

MQTT Client Libraries

MQTT Client Libraries

mosquitto_pub mosquitto_sub co

mqtt.org:

TODO: LIST

Maintained by emqtt.com:

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QoS0, QoS1, QoS2 Messages

C->S Sequence...

Qos is set in both PUBLISH and SUBSCRIBE. The publish message that a subscriber received has the mininum Qos between PUBLISH Qos and SUBSCRIBE Qos as the MQTT v3.1.1 addressed:

The Server might grant a lower maximum QoS than the subscriber requested. The QoS of Payload Messages sent in response to a Subscription MUST be the minimum of the QoS of the originally published message and the maximum QoS granted by the Server.

Retained Message

publish a retained message:

mosquitto_pub -t topic -m msg -q 1 -r

subscribe to get the message:

mosquitto_sub -t topic -m msg -q 1 -r

Will Message

Keep Alive

Clean Session and Offline Messages

MQTT Client Libraries

mosquitto_pub mosquitto_sub co

mqtt.org:

TODO: LIST

Maintained by emqtt.com:

TODO: LIST