In versions of the MQTT protocol lower than 3.1.1, the MQTT server was known as an MQTT broker. Starting in MQTT 3.1.1, the MQTT broker was renamed the MQTT server, and therefore we will refer to it as the server. However, we must take into account that the documentation for MQTT servers, tools, and client libraries can use the old MQTT broker name to refer to the server. MQTT servers are also known as message brokers.
The MQTT server uses the previously explained topic-based filtering to filter and distribute messages to the appropriate subscribers. There are many MQTT server implementations that provide additional message filtering features by providing custom plugins. However, ...
