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| Add-on communication |
There are different ways of communicating between add-ons inside Home Assistant.
Network
We use an internal network that's allowed to communicate with every add-on, including to/from Home Assistant, by using its name or alias. Only add-ons that run on the host network are limited in that they can talk with all internal add-ons by their name, but all other add-ons can't address these add-ons by name. However, using an alias works for both!
Names/aliases are used for communication inside Home Assistant.
The name is generated using the following format: {REPO}_{SLUG}, e.g., local_xy or 3283fh_myaddon. In this example, {SLUG} is defined in an add-on's config.yaml file. You can use this name as the DNS name also, but you need to replace any _ with - to have a valid hostname. If an add-on is installed locally, {REPO} will be local. If the add-on is installed from a Github repository, {REPO} is a hashed identifier generated from the GitHub repository's URL (ex: https://github.com/xy/my_hassio_addons). See here to understand how this identifier is generated. Note that this identifier is required in certain actions that use the Supervisor add-on API. You can view the repository identifiers for all currently installed add-ons via a GET request to the Supervisor API addons endpoint.
Use supervisor for communication with the internal API.
Home Assistant Core
An add-on can talk to the Home Assistant Core API using the internal proxy. This makes it very easy to communicate with the API without knowing the password, port or any other information about the Home Assistant instance. Using this URL: http://supervisor/core/api/ ensures that internal communication is redirected to the right place. The next step is to add homeassistant_api: true to the config.yaml file and read the environment variable SUPERVISOR_TOKEN. Use this as the Home Assistant Core bearer token when making requests.
For example curl -X GET -H "Authorization: Bearer ${SUPERVISOR_TOKEN}" -H "Content-Type: application/json" http://supervisor/core/api/config
There is also a proxy for the Home Assistant Websocket API that works like the API proxy above and requires SUPERVISOR_TOKEN as the password. Use this URL: ws://supervisor/core/websocket.
It is also possible to talk directly to the Home Assistant instance, which is named homeassistant, over the internal network. However, you'll need to know the configuration that is used by the running instance.
We have several actions inside Home Assistant to run tasks. Send data over STDIN to an add-on to use the hassio.addon_stdin action.
Supervisor API
To enable calls to the Supervisor API, add hassio_api: true to the config.yaml file and read the environment variable SUPERVISOR_TOKEN. Now you can use the API over the URL: http://supervisor/. Use the SUPERVISOR_TOKEN with header Authorization: Bearer. You may also need to change the Supervisor API role to hassio_role: default.
Add-ons can call some API commands without needing to set hassio_api: true:
/core/api/core/api/stream/core/websocket/addons/self/*/services*/discovery*/info
Note: For Home Assistant API access requirements, see above.
Services API
We have an internal services API to make services public to other add-ons without the user needing to add any configuration. An add-on can get the full configuration for a service to use and to connect to it. The add-on needs to mark the usage of a service in the add-on configuration in order to be able to access a service. All supported services, including its available options, are documented in the API documentation.
Supported services are:
- mqtt
- mysql
You can use Bashio to get this information for your add-on init as: bashio::services <service> <query>
For example:
MQTT_HOST=$(bashio::services mqtt "host")
MQTT_USER=$(bashio::services mqtt "username")
MQTT_PASSWORD=$(bashio::services mqtt "password")