subscribe(cmd, nodeID) {
		return new this.broker.Promise((resolve, reject) => {
			const topic = this.getTopicName(cmd, nodeID);
			this.client.subscribe(topic, { qos: this.qos }, (err, granted) => {
				if (err) return reject(err);

				this.logger.debug("MQTT server granted", granted);

				resolve();
			});
		});
	}
Subscribe to a command

@param {String} cmd
@param {String} nodeID

@memberof MqttTransporter