60 lines
2.7 KiB
Markdown
60 lines
2.7 KiB
Markdown
---
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layout: page
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title: "Component Discovery"
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description: "How to make component discovery work."
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date: 2017-11-23 07:27 +02:00
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sidebar: true
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comments: false
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sharing: true
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footer: true
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---
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<p class='note warning'>
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This option is only available for built-in components.
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</p>
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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.
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### {% linkable_title Add discovery instructions %}
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Device discovery for Home Assistant has been extracted into an external library called [NetDisco](https://github.com/home-assistant/netdisco). This library is integrated using [the `discovery` component](https://github.com/home-assistant/home-assistant/blob/dev/homeassistant/components/discovery.py) and scans the network in intervals for uPnP and zeroconf/mDNS services.
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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.](https://github.com/home-assistant/netdisco/tree/master/netdisco/discoverables)
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### {% linkable_title Listening to `SERVICE_DISCOVERED` events %}
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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:
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```python
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from homeassistant.components.discovery import SERVICE_AWESOMEDEVICE
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from homeassistant.helpers import discovery
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DOMAIN = 'awesomedevice'
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DEPENDENCIES = ['http']
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def setup(hass, config):
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cfg = config.get(DOMAIN)
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def device_discovered(service, info):
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""" Called when a Awesome device has been discovered. """
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print("Discovered a new Awesome device: {}".format(info))
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discovery.listen(
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hass, SERVICE_AWESOMEDEVICE, device_discovered)
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return True
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```
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### {% linkable_title Auto-loading your component upon discovery %}
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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`](https://github.com/home-assistant/home-assistant/blob/dev/homeassistant/components/discovery.py#L40) constant in [the `discovery` component](https://github.com/home-assistant/home-assistant/blob/dev/homeassistant/components/discovery.py):
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```python
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SERVICE_AWESOMEDEVICE = 'awesomedevice'
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SERVICE_HANDLERS = {
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...
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SERVICE_AWESOMEDEVICE: ('awesomedevice', None),
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}
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```
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