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

---
layout: page
title: "WebSocket API"
description: "Home Assistant WebSocket API documentation"
date: 2016-11-26 13:27
sidebar: true
comments: false
sharing: true
footer: true
---

Home Assistant contains a WebSocket API. This API can be used to stream information from a Home Assistant instance to any client that implements WebSocket. Implementations in different languages:

 - [JavaScript](https://github.com/home-assistant/home-assistant-js-websocket) - powers the frontend
 - [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/)
 - [JavaScript/HTML](https://raw.githubusercontent.com/home-assistant/home-assistant-dev-helper/master/ha-websocket.html) - WebSocket connection in your browser 

Connect your websocket implementation to `ws://localhost:8123/api/websocket`.

## {% linkable_title Server states %}

 1. Client connects
 2. Authentication phase starts
    a. If no further authentication necessary for the user: go to 3
    b. Server sends `auth_required` message
    c. Client sends `auth` message
    d. If `auth` message correct: go to 3.
    e. Server sends `auth_invalid`. Go to 6.
 3. Send `auth_ok` message
 4. Authentication phase ends.
 5. Command phase starts.
    a. Client can send commands.
    b. Server can send results of previous commands.
 6. Client or server disconnects session.

During the command phase, the client attaches a unique identifier to each message. The server will add this identifier to each message so that the client can link each message to it's origin.

## {% linkable_title Message format %}

Each API message is a JSON serialized object containing a `type` key. After the authentication phase messages also must contain an `id`, an integer that contains the number of interactions.

Example of an auth message:

```json
{
  "type": "auth",
  "api_password": "supersecret"
}
```

```json
{
   "id" 5,
   "type":"event",
   "event":{
      "data":{},
      "event_type":"test_event",
      "time_fired":"2016-11-26T01:37:24.265429+00:00",
      "origin":"LOCAL"
   }
}
```

## {% linkable_title Authentication phase %}

When a client connects to the server, the server will test if the client is authenticated. Authentication will not be necessary if no api_password is set or if the user fulfills one of the other criteria for authentication (trusted network, password in url/header).

If no authentication is needed, the authentication phase will complete and the server will send an `auth_ok` message.

```json
{
  "type": "auth_ok"
}
```

If authentication is necessary, the server sends out `auth_required`.

```json
{
  "type": "auth_required"
}
```

This means that the next message from the client should be an auth message:

```json
{
  "type": "auth",
  "api_password": "supersecret"
}
```

If the client supplies valid authentication, the authentication phase will complete by the server sending the `auth_ok` message:

```json
{
  "type": "auth_ok"
}
```

If the data is incorrect, the server will reply with `auth_invalid` message and disconnect the session.

```json
{
  "type": "auth_invalid",
  "message": "Invalid password"
}
```

## {% linkable_title Command phase %}

During this phase the client can give commands to the server. The server will respond to each command with a `result` message indicating when the command is done and if it was successful.

```json
{
  "id": 6.
  "type": "result",
  "success": true,
  // Can contain extra result info
  "result": null
}
```

## {% linkable_title Subscribe to events %}

The command `subscribe_events` will subscribe your client to the event bus. You can either listen to all events or to a specific event type. If you want to listen to multiple event types, you will have to send multiple `subscribe_events` commands.

```json
{
  "id": 18,
  "type": "subscribe_events",
  // Optional
  "event_type": "state_changed"
}
```

The server will respond with a result message to indicate that the subscription is active.

```json
{
  "id": 18,
  "type": "result",
  "success": true,
  "result": null
}
```

For each event that matches, the server will send a message of type `event`. The `id` in the message will point at the original `id` of the `listen_event` command.

```json
{
   "id": 18,
   "type":"event",
   "event":{
      "data":{
         "entity_id":"light.bed_light",
         "new_state":{
            "entity_id":"light.bed_light",
            "last_changed":"2016-11-26T01:37:24.265390+00:00",
            "state":"on",
            "attributes":{
               "rgb_color":[
                  254,
                  208,
                  0
               ],
               "color_temp":380,
               "supported_features":147,
               "xy_color":[
                  0.5,
                  0.5
               ],
               "brightness":180,
               "white_value":200,
               "friendly_name":"Bed Light"
            },
            "last_updated":"2016-11-26T01:37:24.265390+00:00"
         },
         "old_state":{
            "entity_id":"light.bed_light",
            "last_changed":"2016-11-26T01:37:10.466994+00:00",
            "state":"off",
            "attributes":{
               "supported_features":147,
               "friendly_name":"Bed Light"
            },
            "last_updated":"2016-11-26T01:37:10.466994+00:00"
         }
      },
      "event_type":"state_changed",
      "time_fired":"2016-11-26T01:37:24.265429+00:00",
      "origin":"LOCAL"
   }
}
```

### {% linkable_title Unsubscribing from events %}

You can unsubscribe from previously created subscription events. Pass the id of the original subscription command as value to the subscription field.

```json
{
  "id": 19,
  "type": "unsubscribe_events",
  "subscription": 18
}
```

The server will respond with a result message to indicate that unsubscribing was successful.

```json
{
  "id": 19,
  "type": "result",
  "success": true,
  "result": null
}
```


### {% linkable_title Calling a service %}

This will call a service in Home Assistant. Right now there is no return value. The client can listen to `state_changed` events if it is interested in changed entities as a result of a service call.

```json5
{
  "id": 24,
  "type": "call_service",
  "domain": "light",
  "service": "turn_on",
  // Optional
  "service_data": {
    "entity_id": "light.kitchen"
  }
}
```

The server will indicate with a message indicating that the service is done executing.

```json
{
  "id": 24,
  "type": "result",
  "success": true,
  "result": null
}
```

### {% linkable_title Fetching states %}

This will get a dump of all the current states in Home Assistant.

```json
{
  "id": 19,
  "type": "get_states"
}
```

The server will respond with a result message containing the states.

```json
{
  "id": 19,
  "type": "result",
  "success": true,
  "result": [ ... ]
}
```

### {% linkable_title Fetching config %}

This will get a dump of the current config in Home Assistant.

```json
{
  "id": 19,
  "type": "get_config"
}
```

The server will respond with a result message containing the config.

```json
{
  "id": 19,
  "type": "result",
  "success": true,
  "result": { ... }
}
```

### {% linkable_title Fetching services %}

This will get a dump of the current services in Home Assistant.

```json
{
  "id": 19,
  "type": "get_services"
}
```

The server will respond with a result message containing the services.

```json
{
  "id": 19,
  "type": "result",
  "success": true,
  "result": { ... }
}
```

### {% linkable_title Fetching panels %}

This will get a dump of the current registered panels in Home Assistant.

```json
{
  "id": 19,
  "type": "get_panels"
}
```

The server will respond with a result message containing the current registered panels.

```json
{
  "id": 19,
  "type": "result",
  "success": true,
  "result": [ ... ]
}
```

## {% linkable_title Error handling %}

If an error occurs, the `success` key in the `result` message will be set to `false`. It will contain an `error` key containing an object with two keys: `code` and `message`.

| Code | Description |
| ----- | ------------ |
| 1 | A non-increasing identifier has been supplied.
| 2 | Received message is not in expected format (voluptuous validation error).
| 3 | Requested item cannot be found

```json
{
   "id": 12,
   "type":"result",
   "success": false,
   "error": {
      "code": 2,
      "message": "Message incorrectly formatted: expected str for dictionary value @ data['event_type']. Got 100"
   }
}
```