This one is interesting to me as I’m also doing a similar thing and store and forward kind of set up crossed my mind.
So I have numerous Raspberry Pi’s in the field, Some talking to Siemens PLC’s and some with Arduinos attached using various sensors. The plan is to use Node Red to handle all that business.
I was going to set up a broker in the cloud and I’m currently playing with Azure but having issues with the SAS tokens, The Pi’s communicate to the world via a local Cell modem on the site. That’s where the ‘store and forward’ comes in as with it being a cell connection anything could happen and we still want to log the data should that machine be taken further away then the router coverage.
From the above it seems that storing a local version of say Mosquito on the Pi as a broker would be better as the broker does indeed ‘store and forward’?
HiveMQTT has a demo broker available http://www.mqtt-dashboard.com/ for any one playing around with MQTT. I’ve successfully subscribed to some of the published articles in ignition using the cirrus MQTT Engine.
The server URL is tcp://broker.hivemq.com:1883 then set up what articles you want to subscribe to in the Name Spaces then they appear in the designer like Tags to use.