MQTT


MQTT (aka MQ Telemetry Transport) is a machine-to-machine or “Internet of Things” connectivity protocol on top of TCP/IP. It allows extremely lightweight publish/subscribe messaging transport.

Configuration

Adding MQTT to your Home Assistant instance can be done via the user interface, by using this My button:

Your first step to get MQTT and Home Assistant working is to choose a broker.

Choose a MQTT broker

Run your own

The most private option is running your own MQTT broker.

The recommended setup method is to use the Mosquitto MQTT broker add-on.

Neither ActiveMQ MQTT broker nor the RabbitMQ MQTT Plugin are supported, use a known working broker like Mosquitto instead. There are at least two issues with the ActiveMQ MQTT broker which break MQTT message retention.

Connect to a public broker

The Mosquitto project runs a public broker. This is the easiest to set up, but there is no privacy as all messages are public. Use this only for testing purposes and not for real tracking of your devices or controlling your home. To use the public mosquitto broker, configure the MQTT integration to connect to broker test.mosquitto.org on port 1883 or 8883.

If you experience an error message like Failed to connect due to exception: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed, then add certificate: auto to your broker configuration and restart Home Assistant.

Broker configuration

MQTT broker settings are configured when the MQTT integration is first setup, and can be changed if needed. To change the settings, click on “Configure” in the integration page in the UI, then “Re-configure MQTT”.

Advanced broker configuration

Advanced broker configuration options include setting a custom client ID, setting a client certificate and key for authentication and enabling TLS validation of the brokers certificate for. To access the advanced settings, open the MQTT broker settings, switch on Advanced options and click Next. The advanced options will be shown by default if there are advanced settings active already.

Alternative client ID

You can set a custom MQTT client ID, this can help when debugging. Mind that the client ID must be unique. Leave this settings default if you want Home Assistant to generate a unique ID.

Keep alive

The time in seconds between sending keep alive messages for this client. The default is 60 seconds. The keep alive setting should be minimal 15 seconds.

Broker certificate validation

To enable a secure the broker certificate should be validated. If your broker uses a trusted certificate then choose auto. This will allow validation against certifite CAs bundled certificates. If a self-signed certificate is used, select Custom. A custom PEM encoded CA-certificate can be uploaded. Click NEXT to show the control to upload the CA certificate. If the server certificate does not match the hostname then validation will fail. To allow a connection without the verification of the hostname, turn the Ignore broker certificate validation switch on.

Securing the the connection

With a secure broker connection it is possible to use a client certificate for authentication. To set the client certificate and private key turn on the option Use a client certificate and click “Next” to show the controls to upload the files. Only a PEM encoded client certificates together with a PEM encoded private key can be uploaded. Make sure the private key has no password set.

A configured client certificate will only be active if broker certificate validation is enabled.

Configure MQTT options

To change the settings, click on “Configure” in the integration page in the UI, then “Re-configure MQTT”. Click NEXT to open the MQTT options page.

Discovery options

MQTT discovery is enabled by default. Discovery can be turned off. The prefix for the discovery topic (default homeassistant) can be changed here as well. See also MQTT Discovery section

Birth and last will messages

Home Assistant’s MQTT integration 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 a disconnected client. Please note that the LWT message will be sent both in case of a clean (e.g. Home Assistant shutting down) and in case of an unclean (e.g. Home Assistant crashing or losing its network connection) disconnect.

By default, Home Assistant sends online and offline to homeassistant/status.

MQTT Birth and Last Will messages can be customized or disabled from the UI. To do this, click on “Configure” in the integration page in the UI, then “Re-configure MQTT” and then “Next”.

Testing your setup

The mosquitto broker package ships commandline tools (often as *-clients package) to send and receive MQTT messages. For sending test messages to a broker running on localhost check the example below:

mosquitto_pub -h 127.0.0.1 -t home-assistant/switch/1/on -m "Switch is ON"

Another way to send MQTT messages manually is to use the “MQTT” integration in the frontend. Choose “Settings” on the left menu, click “Devices & Services”, and choose “Configure” in the “Mosquitto broker” tile. Enter something similar to the example below into the “topic” field under “Publish a packet” and press “PUBLISH” .

   home-assistant/switch/1/power

and in the Payload field

   ON

In the “Listen to a topic” field, type # to see everything, or “home-assistant/switch/#” to just follow a published topic, then press “START LISTENING”. The messages should appear similar to the text below:

Message 23 received on home-assistant/switch/1/power/stat/POWER at 12:16 PM:
ON
QoS: 0 - Retain: false
Message 22 received on home-assistant/switch/1/power/stat/RESULT at 12:16 PM:
{
    "POWER": "ON"
}
QoS: 0 - Retain: false

For reading all messages sent on the topic home-assistant to a broker running on localhost:

mosquitto_sub -h 127.0.0.1 -v -t "home-assistant/#"

MQTT Discovery

The discovery of MQTT devices will enable one to use MQTT devices with only minimal configuration effort on the side of Home Assistant. The configuration is done on the device itself and the topic used by the device. Similar to the HTTP binary sensor and the HTTP sensor. To prevent multiple identical entries if a device reconnects, a unique identifier is necessary. Two parts are required on the device side: The configuration topic which contains the necessary device type and unique identifier, and the remaining device configuration without the device type.

MQTT discovery is enabled by default, but can be disabled. The prefix for the discovery topic (default homeassistant) can be changed. See the MQTT Options sections

Discovery messages

Discovery topic

The discovery topic needs to follow a specific format:

<discovery_prefix>/<component>/[<node_id>/]<object_id>/config
  • <component>: One of the supported MQTT components, eg. binary_sensor.
  • <node_id> (Optional): ID of the node providing the topic, this is not used by Home Assistant but may be used to structure the MQTT topic. The ID of the node must only consist of characters from the character class [a-zA-Z0-9_-] (alphanumerics, underscore and hyphen).
  • <object_id>: The ID of the device. This is only to allow for separate topics for each device and is not used for the entity_id. The ID of the device must only consist of characters from the character class [a-zA-Z0-9_-] (alphanumerics, underscore and hyphen).

The <node_id> level can be used by clients to only subscribe to their own (command) topics by using one wildcard topic like <discovery_prefix>/+/<node_id>/+/set.

Best practice for entities with a unique_id is to set <object_id> to unique_id and omit the <node_id>.

Discovery payload

The payload must be a serialized JSON dictionary and will be checked like an entry in your configuration.yaml file if a new device is added, with the exception that unknown configuration keys are allowed but ignored. This means that missing variables will be filled with the platform’s default values. All configuration variables which are required must be present in the payload. The reason for allowing unknown documentation keys is allow some backwards compatibility, software generating MQTT discovery messages can then be used with older Home Assistant versions which will simply ignore new features.

Subsequent messages on a topic where a valid payload has been received will be handled as a configuration update, and a configuration update with an empty payload will cause a previously discovered device to be deleted.

A base topic ~ may be defined in the payload to conserve memory when the same topic base is used multiple times. In the value of configuration variables ending with _topic, ~ will be replaced with the base topic, if the ~ occurs at the beginning or end of the value.

Configuration variable names in the discovery payload may be abbreviated to conserve memory when sending a discovery message from memory constrained devices.

Support by third-party tools

The following software has built-in support for MQTT discovery:

Discovery examples

Motion detection (binary sensor)

A motion detection device which can be represented by a binary sensor for your garden would send its configuration as JSON payload to the Configuration topic. After the first message to config, then the MQTT messages sent to the state topic will update the state in Home Assistant.

  • Configuration topic: homeassistant/binary_sensor/garden/config
  • State topic: homeassistant/binary_sensor/garden/state
  • Payload: {"name": "garden", "device_class": "motion", "state_topic": "homeassistant/binary_sensor/garden/state"}
  • Retain: The -r switch is added to retain the configuration topic in the broker. Without this, the sensor will not be available after Home Assistant restarts.

To create a new sensor manually.

mosquitto_pub -r -h 127.0.0.1 -p 1883 -t "homeassistant/binary_sensor/garden/config" -m '{"name": "garden", "device_class": "motion", "state_topic": "homeassistant/binary_sensor/garden/state"}'

Update the state.

mosquitto_pub -h 127.0.0.1 -p 1883 -t "homeassistant/binary_sensor/garden/state" -m ON

Delete the sensor by sending an empty message.

mosquitto_pub -h 127.0.0.1 -p 1883 -t "homeassistant/binary_sensor/garden/config" -m ''

For more details please refer to the MQTT testing section.

Sensors

Setting up a sensor with multiple measurement values requires multiple consecutive configuration topic submissions.

  • Configuration topic no1: homeassistant/sensor/sensorBedroomT/config
  • Configuration payload no1: {"device_class": "temperature", "name": "Temperature", "state_topic": "homeassistant/sensor/sensorBedroom/state", "unit_of_measurement": "°C", "value_template": "{{ value_json.temperature}}" }
  • Configuration topic no2: homeassistant/sensor/sensorBedroomH/config
  • Configuration payload no2: {"device_class": "humidity", "name": "Humidity", "state_topic": "homeassistant/sensor/sensorBedroom/state", "unit_of_measurement": "%", "value_template": "{{ value_json.humidity}}" }
  • Common state payload: { "temperature": 23.20, "humidity": 43.70 }

Entities with command topics

Setting up a light, switch etc. is similar but requires a command_topic as mentioned in the MQTT switch documentation.

  • Configuration topic: homeassistant/switch/irrigation/config
  • State topic: homeassistant/switch/irrigation/state
  • Command topic: homeassistant/switch/irrigation/set
  • Payload: {"name": "garden", "command_topic": "homeassistant/switch/irrigation/set", "state_topic": "homeassistant/switch/irrigation/state"}
  • Retain: The -r switch is added to retain the configuration topic in the broker. Without this, the sensor will not be available after Home Assistant restarts.
mosquitto_pub -r -h 127.0.0.1 -p 1883 -t "homeassistant/switch/irrigation/config" \
  -m '{"name": "garden", "command_topic": "homeassistant/switch/irrigation/set", "state_topic": "homeassistant/switch/irrigation/state"}'

Set the state.

mosquitto_pub -h 127.0.0.1 -p 1883 -t "homeassistant/switch/irrigation/set" -m ON

Using abbreviations and base topic

Setting up a switch using topic prefix and abbreviated configuration variable names to reduce payload length.

  • Configuration topic: homeassistant/switch/irrigation/config
  • Command topic: homeassistant/switch/irrigation/set
  • State topic: homeassistant/switch/irrigation/state
  • Configuration payload: {"~": "homeassistant/switch/irrigation", "name": "garden", "cmd_t": "~/set", "stat_t": "~/state"}

Another example using abbreviations topic name and base topic

Setting up a light that takes JSON payloads, with abbreviated configuration variable names:

  • Configuration topic: homeassistant/light/kitchen/config

  • Command topic: homeassistant/light/kitchen/set

  • State topic: homeassistant/light/kitchen/state

  • Example state payload: {"state": "ON", "brightness": 255}

  • Configuration payload:

    {
      "~": "homeassistant/light/kitchen",
      "name": "Kitchen",
      "unique_id": "kitchen_light",
      "cmd_t": "~/set",
      "stat_t": "~/state",
      "schema": "json",
      "brightness": true
    }
    

Use object_id to influence the entity id

The entity id is automatically generated from the entity’s name. All MQTT entity components optionally support providing an object_id which will be used instead if provided.

  • Configuration topic: homeassistant/sensor/device1/config
  • Example configuration payload:
{
  "name":"My Super Device",
  "object_id":"my_super_device",
  "state_topic": "homeassistant/sensor/device1/state"
 }

In the example above, the entity_id will be sensor.my_super_device instead of sensor.device1.

Manual configured MQTT items

For most platforms it is also possible to manual set up MQTT items in configuration.yaml. Read more about configuration in YAML.

If you have a lot of manual configured items you might want to consider splitting up the configuration.

Using Templates

The MQTT platform support templating. Read more about using templates with the MQTT integration.

MQTT Notifications

The MQTT notification support is different than the other notification platforms. It is a service. This means that you don’t have to create a configuration entry but you need to provide more details when calling the service.

Call Service section from Developer Tools -> Services allows you to send MQTT messages. Choose mqtt.publish from the list of Available services: and enter something like the sample below into the Service Data field and hit CALL SERVICE.

{"payload": "Test message from HA", "topic": "home/notification", "qos": 0, "retain": 0}

The same will work for automations.

Examples

REST API

Using the REST API to send a message to a given topic.

$ curl -X POST \
    -H "Authorization: Bearer ABCDEFGH" \
    -H "Content-Type: application/json" \
    -d '{"payload": "Test message from HA", "topic": "home/notification"}' \
    http://IP_ADDRESS:8123/api/services/mqtt/publish

Automations

Use as script in automations.

automation:
  alias: "Send me a message when I get home"
  trigger:
    platform: state
    entity_id: device_tracker.me
    to: "home"
  action:
    service: script.notify_mqtt
    data:
      target: "me"
      message: "I'm home"

script:
  notify_mqtt:
    sequence:
      - service: mqtt.publish
        data:
          payload: "{{ message }}"
          topic: home/"{{ target }}"
          retain: true

Publish & Dump services

The MQTT integration will register the service mqtt.publish which allows publishing messages to MQTT topics. There are two ways of specifying your payload. You can either use payload to hard-code a payload or use payload_template to specify a template that will be rendered to generate the payload.

Service mqtt.publish

Service data attribute Optional Description
topic no Topic to publish payload to.
topic_template no Template to render as topic to publish payload to.
payload yes Payload to publish.
payload_template yes Template to render as payload value.
qos yes Quality of Service to use. (default: 0)
retain yes If message should have the retain flag set. (default: false)

You must include either `topic` or `topic_template`, but not both. If providing a payload, you need to include either `payload` or `payload_template`, but not both.

topic: home-assistant/light/1/command
payload: on
topic: home-assistant/light/1/state
payload_template: "{{ states('device_tracker.paulus') }}"
topic_template: "home-assistant/light/{{ states('sensor.light_active') }}/state"
payload_template: "{{ states('device_tracker.paulus') }}"

payload must be a string. If you want to send JSON then you need to format/escape it properly. Like:

topic: home-assistant/light/1/state
payload: "{\"Status\":\"off\", \"Data\":\"something\"}"

Example of how to use qos and retain:

topic: home-assistant/light/1/command
payload: on
qos: 2
retain: true

Service mqtt.dump

Listen to the specified topic matcher and dumps all received messages within a specific duration into the file mqtt_dump.txt in your configuration folder. This is useful when debugging a problem.

Service data attribute Optional Description
topic no Topic to dump. Can contain a wildcard (# or +).
duration yes Duration in seconds that we will listen for messages. Default is 5 seconds.
topic: openzwave/#

Logging

The logger integration allows the logging of received MQTT messages.

# Example configuration.yaml entry
logger:
  default: warning
  logs:
    homeassistant.components.mqtt: debug

Event event_mqtt_reloaded

Event event_mqtt_reloaded is fired when Manually configured MQTT entities have been reloaded and entities thus might have changed.

This event has no additional data.