When the Edge MQTT app is deployed without the MQTTS Bridge parameter defined, then the app runs as a standard MQTT message broker at the edge. Since it uses Mosquitto it is both lightweight and suitable for use on all devices, and provides a lightweight method of carrying out messaging using a publish/subscribe model.
When running with bridging enabled, the Edge MQTT application can receive MQTT messages from local nodes and applications, and forward them to an external MQTT broker. The advantage of using Edge MQTT in this way is that it can prevent message loss in the case of a network outage. When the external MQTT broker becomes unavailable (for example, because of a configuration errors, or the WAN connection of the site is temporarily down), Edge MQTT can store the incoming messages, and automatically transmit them when the broker becomes available.