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Update the WS API docs (#937)
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Paulus Schoutsen
GitHub
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@ -2,15 +2,7 @@
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title: "WebSocket API"
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---
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Home Assistant contains a WebSocket API. This API can be used to stream information from a Home Assistant instance to any client that implements WebSockets. Implementations in different languages:
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- [JavaScript](https://github.com/home-assistant/home-assistant-js-websocket) - powers the frontend
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- [Python](https://raw.githubusercontent.com/home-assistant/home-assistant-dev-helper/master/ha-websocket-client.py) - CLI client using [`asyncws`](https://async-websockets.readthedocs.io/en/latest/)
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- [JavaScript/HTML](https://raw.githubusercontent.com/home-assistant/home-assistant-dev-helper/master/ha-websocket.html) - WebSocket connection in your browser
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Connect your websocket implementation to `ws://localhost:8123/api/websocket`. You will need a valid access token.
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If you are not using the [`frontend`](https://www.home-assistant.io/components/frontend/) in your setup then you need to add the [`websocket_api` component](https://www.home-assistant.io/components/websocket_api/) to your `configuration.yaml` file to use the WebSocket API.
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Home Assistant contains a WebSocket API. This API can be used to stream information from a Home Assistant instance to any client that implements WebSockets. We maintain a [JavaScript library](https://github.com/home-assistant/home-assistant-js-websocket) which we use in our frontend.
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## Server states
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@ -61,7 +53,8 @@ When a client connects to the server, the server sends out `auth_required`.
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```json
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{
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"type": "auth_required"
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"type": "auth_required",
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"ha_version": "2021.5.3"
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}
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```
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@ -78,7 +71,8 @@ If the client supplies valid authentication, the authentication phase will compl
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```json
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{
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"type": "auth_ok"
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"type": "auth_ok",
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"ha_version": "2021.5.3"
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}
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```
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@ -8,104 +8,73 @@ As a component you might have information that you want to make available to the
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To register a command, you need to have a message type, a message schema and a message handler. Your component does not have to add the websocket API as a dependency. You register your command, and if the user is using the websocket API, the command will be made available.
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### Message Types
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### Defining your command schema
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Message types are made up the domain and the message type, separated by a forward slash. In the below example, we're defining `media_player/thumbnail`.
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A command schema is made up of a message type and what type of data we expect when the command is invoked. You define both the command type and the data schema via a decorator on your command handler. Message handlers are callback functions that are run inside the event loop.
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```python
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# The type of the message
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WS_TYPE_MEDIA_PLAYER_THUMBNAIL = "media_player/thumbnail"
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```
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### Message Schema
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The message schema defines what type of data we expect when the message is invoked. It is defined as a voluptuous schema and has to extend the base web socket command schema.
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```python
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import voluptuous as vol
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from homeassistant.components import websocket_api
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import homeassistant.helpers.config_validation as cv
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# The schema for the message
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SCHEMA_WEBSOCKET_GET_THUMBNAIL = websocket_api.BASE_COMMAND_MESSAGE_SCHEMA.extend(
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@websocket_api.websocket_command(
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{
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"type": WS_TYPE_MEDIA_PLAYER_THUMBNAIL,
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# The entity that we want to retrieve the thumbnail for.
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"entity_id": cv.entity_id,
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vol.Required("type"): "frontend/get_panels",
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vol.Optional("preload_panels"): bool,
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}
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)
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@callback
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def ws_get_panels(
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hass: HomeAssistant, connection: websocket_api.ActiveConnection, msg: dict
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) -> None:
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"""Handle the websocket command."""
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panels = ...
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connection.send_result(msg["id"], {"panels": panels})
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```
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### Defining a handler
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#### Doing I/O or sending a delayed response
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Message handlers are callback functions that are run inside the event loop. If you want to do I/O or have to wait for your result, create a new function and queue it up using `hass.async_add_job`. This is done so that the websocket API can get back to handling the next message as soon as possible.
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#### Sending a direct response
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If you are defining a command that is querying simple information, you might be able to fulfill the request while the handler is being called by the websocket API. To do this, use `connection.to_write.put_nowait`.
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If your command needs to interact with the network, a device or needs to compute information, you will need to queue a job to do the work and send the response. To do this, make your function async and decorate with `@websocket_api.async_response`.
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```python
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@callback
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def websocket_handle_thumbnail(hass, connection, msg):
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"""Handle getting a thumbnail."""
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from homeassistant.components import websocket_api
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# We know the answer without having to fetch any information,
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# so we send it directly.
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connection.to_write.put_nowait(
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websocket_api.result_message(
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msg["id"], {"thumbnail": "http://via.placeholder.com/350x150"}
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)
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)
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```
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#### Sending a delayed response
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If your command needs to interact with the network, a device or needs to compute information, you will need to queue a job to do the work and send the response. To do this, use `connection.send_message_outside`.
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```python
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@callback
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def websocket_handle_thumbnail(hass, connection, msg):
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@websocket_api.websocket_command(
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{
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vol.Required("type"): "camera/get_thumbnail",
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vol.Optional("entity_id"): str,
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}
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)
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@websocket_api.async_response
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async def ws_handle_thumbnail(
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hass: HomeAssistant, connection: ActiveConnection, msg: dict
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) -> None:
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"""Handle get media player cover command."""
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# Retrieve media player using passed in entity id.
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player = hass.data[DOMAIN].get_entity(msg["entity_id"])
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# If the player does not exist, send an error message.
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if player is None:
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connection.to_write.put_nowait(
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websocket_api.error_message(
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connection.send_error(
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msg["id"], "entity_not_found", "Entity not found"
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)
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)
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return
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# Define a function to be enqueued.
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async def send_image():
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"""Send image."""
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data, content_type = await player.async_get_media_image()
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data, content_type = await player.async_get_media_image()
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# No media player thumbnail available
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if data is None:
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connection.send_message_outside(
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websocket_api.error_message(
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msg["id"], "thumbnail_fetch_failed", "Failed to fetch thumbnail"
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)
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)
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return
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connection.send_message_outside(
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websocket_api.result_message(
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msg["id"],
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{
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"content_type": content_type,
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"content": base64.b64encode(data).decode("utf-8"),
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},
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)
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# No media player thumbnail available
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if data is None:
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connection.send_error(
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msg["id"], "thumbnail_fetch_failed", "Failed to fetch thumbnail"
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)
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return
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# Player exist. Queue up a job to send the thumbnail.
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hass.async_add_job(send_image())
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connection.send_result(
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msg["id"],
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{
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"content_type": content_type,
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"content": base64.b64encode(data).decode("utf-8"),
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},
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)
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```
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### Registering with the Websocket API
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@ -115,11 +84,8 @@ With all pieces defined, it's time to register the command. This is done inside
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```python
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async def async_setup(hass, config):
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"""Setup of your component."""
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hass.components.websocket_api.async_register_command(
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WS_TYPE_MEDIA_PLAYER_THUMBNAIL,
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websocket_handle_thumbnail,
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SCHEMA_WEBSOCKET_GET_THUMBNAIL,
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)
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hass.components.websocket_api.async_register_command(ws_get_panels)
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hass.components.websocket_api.async_register_command(ws_handle_thumbnail)
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```
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## Calling the command from the frontend (JavaScript)
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