[PUBLISH] queue publishes while offline

[YoDaMa]

You don't have to wait until you establish a connection before you start publishing. MQTT.js queues up all messages you publish in your outgoing store until it actually connects and then it publishes them for you.

https://github.com/mqttjs/MQTT.js/issues/676#issuecomment-327367623

[YoDaMa]

https://stackoverflow.com/questions/38737217/how-to-store-data-mqtt-when-offline-and-send-them-when-online