# Broker

The broker will act as an intermediary between OpenMQTTGateway and your controller, it can be seen as a centralized hub at the heart of your automation system. It carry on messages following a publish / subscribe mechanism.

All the events or commands could pass by the broker.

There is many choice of brokers, here is some of the most populars:

This wikipedia list gives you more details about the different choices you have. This github list seems to be the most exhaustive ones. Here is also some idea of criterias from HiveMQ.

Once your broker installed it can be interesting to see the traffic passing to it and to publish data, so as to do that there is several tools available: