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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
Publish/Subscribe Model¶
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:
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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