MQTT Broker server on Node-RED
Because this MQTT broker is implemented by Node.js, you can use MQTT-in and MQTT-out nodes without MQTT environment like Mosquitto.
Once you just put this node on Node-RED and hit deploy button, MQTT Broker will run on your Node-RED.
You can set "localhost" in MQTT-in and MQTT-out properties as follows.
In the "manage palette", Node-RED users can install the node using "mqtt-broker" as the keyword.