Not only can you restrict access to the Mosquitto MQTT broker using a username and password you can also restrict access to topics using an ACL (Access control list). Unless you are running an open broker you will want to restrict access to topics so that only authorized users/clients can publish or subscribe to them. Topic restrictions are configured on the Broker, and there is nothing to configure on the client. Topic restriction is done in an access control list ( ACL ) file. To enable topic restrictions you need to edit the mosquitto.conf file to use it. Note: You … Continue reading Mosquitto ACL -Configuring and Testing MQTT Topic Restrictions