home-assistant.io/source/_docs/mqtt/birth_will.markdown

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MQTT Birth and Last will	Instructions on how to setup MQTT birth and last will messages within Home Assistant.	mqtt.png

MQTT supports so-called Birth and Last Will and Testament (LWT) messages. The former is used to send a message after the service has started, and the latter is used to notify other clients about an ungracefully disconnected client.

To integrate MQTT Birth and Last Will messages into Home Assistant, add the following section to your configuration.yaml file:

# Example configuration.yaml entry
mqtt:
  birth_message:
    topic: 'hass/status'
    payload: 'online'
  will_message:
    topic: 'hass/status'
    payload: 'offline'

{% configuration %} birth_message: description: Birth Message. required: false type: list keys: topic: description: The MQTT topic to publish the message. required: true type: string payload: description: The message content. required: true type: string qos: description: The maximum QoS level of the topic. required: false default: 0 type: integer retain: description: If the published message should have the retain flag on or not. required: false default: false type: boolean will_message: description: Will Message required: false type: list keys: topic: description: The MQTT topic to publish the message. required: true type: string payload: description: The message content. required: true type: string qos: description: The maximum QoS level of the topic. required: false default: 0 type: integer retain: description: If the published message should have the retain flag on or not. required: false default: false type: boolean {% endconfiguration %}