Agnostic Payload for Flexible Delivery: The payload can be in any format, binary, text, picture data.
Message retaining for last value caching: Client can ask MQTT broker to retain the last message it sent
The message almost looks like below
CONNECT id=thing1
PUBLISH thing1/battery {“value” : “95”} RETAIN
PUBLISH thing1/battery {“value” : “94”} RETAIN
PUBLISH thing1/battery {“value” : “93”} RETAIN
DISCONNECT
CONNECT ID=thing2
SUBSCRIBE thing1/battery
<- :="" battery="" nbsp="" publish="" span="" thing1="" value="">
MQTT has client ID and cleanSession for Session State
CONNECT ID=thing1, cleanSession=FALSE
SUBSCRIBE chat/myRoom QoS=2
DISCONNECT
CONNECT ID=thing2
PUBLISH chat/myRoom “Hello Thing1” QoS=1
PUBLISH chat/myRoom “Are you there?” QoS=2
CONNECT ID=thing1, cleanSession=FALSE
chat/myRoom “Hellow thing1” PUBLISH
chat/myRoom “Are you there?” PUBLISH
PUBLISH chat/myRoom “Am there now!” QoS=1
MQTT has last will and testament for presence
CONNECT ID=thing2
SUBSCRIBE thing1/status
CONNECT ID=thing1 LWT=thing1/status “Bye”
PINGREQ ->
<- nbsp="" pingres="" span="">
(client now has network problem)
(keep alive seconds pass)
<- bye="" nbsp="" publish="" span="" status="" thing1="">
References:
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