MQTT (or Eclipse Mosquitto) is a lightweight messaging protocol that is designed for use in constrained devices and low-bandwidth, high-latency, or unreliable networks. It is commonly used in Internet of Things (IoT) devices/applications for efficient and reliable communication between devices.
Also, MQTT does not have a web interface, so you will need to use a client to interact with it.
You can connect MQTT to Home Assistant and Node Red via docker hostname. Add the MQTT integration in Home Assistant and use mqtt as the hostname/Broker, and 1883 as the port. In Node Red, you can use the mqtt node to connect to the MQTT server.
While MQTT can be set up to use a username and password, it is not recommended to expose it to the internet. So by default, MQTT is not exposed to the internet, nor does it have a username and password.
To add a username and password, you will need to edit the mosquitto.conf file. You can find the file in the /opt/mqtt/config/ directory. You will need to add the following lines to the file: