Mqtt

The “Mqtt” object in the Smart Home project provides the ability to publish messages to an MQTT broker.

Quality of Service in MQTT (QoS)

QoS 0: At most once. At this level, the publisher sends the message to the broker once and does not wait for confirmation. It means “fire and forget.”

QoS 1: At least once. This level guarantees that the message will be delivered to the broker, but there is a possibility of message duplication from the publisher. When the broker receives a duplicate message, it resends it to the subscribers and sends an acknowledgment to the publisher. If the publisher doesn’t receive a PUBACK message from the broker, it resends the packet with the DUP flag set to “1.”

QoS 2: Exactly once. This level guarantees the delivery of messages to the subscriber and eliminates the possibility of duplicating sent messages.

The “Mqtt” object in the Smart Home project provides the following method:

1. publish(topic, payload, qos, retain): This method is used to publish messages to an MQTT broker. You pass the arguments topic (the topic), payload (the message content), qos (Quality of Service level), and retain (the “retain” flag).

• topic: A string representing the topic to which the message will be published.
• payload: The content of the message, which can be a string, an object, or binary data.
• qos: The Quality of Service level determines the message delivery guarantees. Possible values are 0 (at most once), 1 (at least once with acknowledgment), or 2 (exactly once with retransmission if needed).
• retain: A flag indicating whether the message should be retained on the broker and sent to new subscribers. Values can be true (retain) or false (do not retain).

Usage example:

const topic = 'smart-home/living-room/light';
const payload = 'on';
const qos = 1;
const retain = true;

Mqtt.publish(topic, payload, qos, retain);

The publish method allows you to send messages to an MQTT broker for transmitting information and controlling devices or the system as a whole in your Smart Home project.

Mqtt object

# Publish a message
Mqtt
  .publish(topic, payload, qos, retain)

Code Example

# mqtt
# ##################################

payload = JSON.stringify({"state": actionName})
Mqtt.publish"zigbee2mqtt/device/set", payload, 0, false)