MQTT: Message queuing at server side -


i using mqtt implement 1 of kind of email notification system. planning use trigger notifications inside webapp. confused between whether mqtt stores data @ server side when throw on mqtt url publisher id in json format? reason asking because in case, mqtt stores last thrown data, if send 1 previous 1 disappeared. want know present @ mqtt side birth(as mq stands message queuing) & haven't used or need implemented @ server/consumer side?

there common error on internet ... mqtt stands mq telemetry transport , not message queueing telemetry transport. created ibm (with eurotech) , part of mq products family in ibm. mqtt hasn't queue. broker receives message on topic , forwards on subscribers on topic. there 2 main variations on behaviour:

  • if publisher send message "retain" flag active, broker store message (only this). if client subscribes topic, broker sends last storage message. it's called "last known message"
  • if subscriber connects broker "clean session" false, broker saves subscriptions , messages if client offline. it's queue not queue. "clean session" false, if client goes offline publishers send messages topic subscribed, broker store these messages. when client returns online, receive messages lost.

paolo.


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