Now, we will configure Mosquitto to work with WebSockets. First, we will work with WebSockets without TLS, and therefore, the communications between the client and Mosquitto through WebSockets will be unsecure. This way, any client that knows the host name and port will be able to establish a communication with the Mosquitto server.
In case you are running the Mosquitto server in a Terminal window in macOS or Linux, press Ctrl+C to stop it. In Windows, stop the appropriate service.
Go to the Mosquitto installation directory and open the mosquitto.conf configuration file. In Chapter 2, Securing an MQTT Mosquitto Server, we learned that it is a good practice to make a backup copy of the existing mosquitto.conf configuration file before making changes to it. This way, we can easily roll back to the previous configuration if something goes wrong.
In macOS, Linux, or Windows, add the following lines at the end of the configuration file:
listener 9001...