home-assistant.io/source/developers/component_discovery.markdown

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layout	title	description	date	sidebar	comments	sharing	footer
page	Component Discovery	How to make component discovery work.	2017-11-23 07:27 +02:00	true	false	true	true

This option is only available for built-in components.

Home Assistant has a discovery service running in the background to discover new devices. Whenever a new device is discovered, a SERVICE_DISCOVERED event will be fired with the found service and the information. The discovery component has some knowledge about which components handle which type of services and will ensure those are loaded and listening before firing the SERVICE_DISCOVERED event.

{% linkable_title Add discovery instructions %}

Device discovery for Home Assistant has been extracted into an external library called NetDisco. This library is integrated using the discovery component and scans the network in intervals for uPnP and zeroconf/mDNS services.

To have your device be discovered, you will have to extend the NetDisco library to be able to find your device. This is done by adding a new discoverable. See the repository for examples of existing discoverable.

{% linkable_title Listening to SERVICE_DISCOVERED events %}

From your component, you will have to set up the listening for specific services. Given below is an example how one would listen for a discovered AwesomeDevice:

from homeassistant.components.discovery import SERVICE_AWESOMEDEVICE
from homeassistant.helpers import discovery

DOMAIN = 'awesomedevice'

DEPENDENCIES = ['http']

def setup(hass, config):
    cfg = config.get(DOMAIN)

    def device_discovered(service, info):
        """ Called when a Awesome device has been discovered. """
        print("Discovered a new Awesome device: {}".format(info))

    discovery.listen(
        hass, SERVICE_AWESOMEDEVICE, device_discovered)

    return True

{% linkable_title Auto-loading your component upon discovery %}

The discovery component is capable of setting up your components before firing the EVENT_PLATFORM_DISCOVERED event. To do this you will have to update the SERVICE_HANDLERS constant in the discovery component:

SERVICE_AWESOMEDEVICE = 'awesomedevice'

SERVICE_HANDLERS = {
    ...
    SERVICE_AWESOMEDEVICE: ('awesomedevice', None),
}