public int getMqttPort() {
        return this.getMappedPort(MQTT_PORT);
    }
Get the mapped port for the MQTT port of the container.
<p>
Must be called after the container is started.

@return the port on the host machine for mqtt clients to connect
modules/hivemq/src/main/java/org/testcontainers/hivemq/HiveMQContainer.java