home-assistant-js-websocket

:aerial_tramway: JavaScript websocket client for Home Assistant

This is a websocket client written in JavaScript that allows retrieving authentication tokens and communicate with the Home Assistant websocket API. It can be used to integrate Home Assistant into your apps. It has 0 dependencies.

Trying it out

We've included an example client based on this lib so that it's easy to try it out:

yarn build
npx http-server -o
# A browser will open, navigate to example.html

Usage

Initializing connection

To initialize a connection, you need an authentication token for the instance that you want to connect to. This library implements the necessary steps to guide the user to authenticate your website with their Home Assistant instance and give you a token. All you need from the user is ask the url of their instance.

// Example connect code
import {
  getAuth,
  createConnection,
  subscribeEntities,
  ERR_HASS_HOST_REQUIRED
} from "home-assistant-js-websocket";

async function connect() {
  let auth;
  try {
    auth = await getAuth();
  } catch (err) {
    if (err === ERR_HASS_HOST_REQUIRED) {
      const hassUrl = prompt(
        "What host to connect to?",
        "http://localhost:8123"
      );
      auth = await getAuth({ hassUrl });
    } else {
      alert(`Unknown error: ${err}`);
      return;
    }
  }
  const connection = await createConnection({ auth });
  subscribeEntities(connection, ent => console.log(ent));
}

connect();

Connections to the websocket API are initiated by calling createConnection(options). This method will return a promise that will resolve to either a Connection object or rejects with error codes ERR_INVALID_AUTH or ERR_CANNOT_CONNECT.

Available options

Currently the following options are available:

Option	Description
setupRetry	Number of times to retry initial connection when it fails. Set to -1 for infinite retries. Default is 0 (no retries)
createSocket	Override the createSocket method with your own. (auth, options) => Promise<WebSocket>

Possible error codes

Currently the following error codes can be expected:

Error	Description
ERR_CANNOT_CONNECT	If the client was unable to connect to the websocket API.
ERR_INVALID_AUTH	If the supplied authentication was invalid.
ERR_CONNECTION_LOST	Raised if connection closed while waiting for a message to be returned.
ERR_HASS_HOST_REQUIRED	If the authentication requires a host to be defined.

You can import them into your code as follows:

import {
  ERR_CANNOT_CONNECT,
  ERR_INVALID_AUTH
} from "home-assistant-js-websocket";

Automatic reconnecting

The connection object will automatically try to reconnect to the server when the connection gets lost. On reconnect, it will automatically resubscribe the event listeners.

The Connection object implements three events related to the reconnecting logic.

Event	Data	Description
ready	-	Fired when authentication is successful and the connection is ready to take commands.
disconnected	-	Fired when the connection is lost.
reconnect-error	Error code	Fired when we encounter a fatal error when trying to reconnect. Currently limited to ERR_INVALID_AUTH.

You can attach and remove listeners as follows:

function eventHandler(connection, data) {
  console.log("Connection has been established again");
}

conn.addEventListener("ready", eventHandler);
conn.removeEventListener("ready", eventHandler);

Entities

You can subscribe to the entities of Home Assistant. Your callback will be called when the entities are first loaded and on every change to the state of any of the entities after that. The callback will be called with a single object that contains the entities keyed by entity_id.

The function subscribeEntities will return an unsubscribe function.

import { subscribeEntities } from "home-assistant-js-websocket";

// conn is the connection from earlier.

subscribeEntities(conn, entities => console.log("New entities!", entities));

Config

You can subscribe to the config of Home Assistant. Config can change when either a component gets loaded.

The function subscribeConfig will return an unsubscribe function.

import { subscribeConfig } from "home-assistant-js-websocket";

// conn is the connection from earlier.

subscribeConfig(conn, config => console.log("New config!", config));

Services

You can subscribe to the available services of Home Assistant. Services can change when a new service gets registered or removed.

The function subscribeServices will return an unsubscribe function.

import { subscribeServices } from "home-assistant-js-websocket";

// conn is the connection from earlier.

subscribeServices(conn, services => console.log("New services!", services));

Collections

Besides entities, config and services you might want to create your own collections. A collection has the following features:

• Fetch a full data set on initial creation and on reconnect
• Subscribe to events to keep collection up to date
• Share subscription between multiple listeners

createCollection(
  key: string,
  fetchCollection: (conn: Connection) => Promise<State>,
  subscribeUpdates: (
    conn: Connection,
    store: Store<State>
  ) => Promise<() => void>,
  conn: Connection,
  onChange: (state: State) => void
)

• key a unique key for the collection
• fetchCollection needs to return a Promsise that resolves to the full state
• subscribeUpdates needs to subscribe to the updates and update the store. Returns a promise that resolves to an unsubscribe function.
• conn is the connection to subscribe to.
• onChange is the callback to be called when collection is changed.

The idea is that your collection code creates a function that fills in the first three parameters and then exposes a subscribeX(conn, onChange) function for other code to call.

Collection Example

import { createCollection } from "home-assistant-js-websocket";

function panelRegistered(state, event) {
  // Returning null means no change.
  if (state === undefined) return null;

  // This will be merged with the existing state.
  return {
    panels: state.panels.concat(event.data.panel)
  };
}

const fetchPanels = conn => conn.sendMessagePromise({ type: "get_panels" });
const subscribeUpdates = (conn, store) =>
  conn.subscribeEvents(store.action(panelRegistered), "panel_registered");

const subscribePanels = (conn, onChange) =>
  createCollection("_pnl", fetchPanels, subscribeUpdates, conn, onChange);

// Now use collection
subscribePanels(conn, panels => console.log("New panels!", panels));

Collections are useful to define if data is needed for initial data load. You can create a collection and have code on your page call it before you start rendering the UI. By the time UI is loaded, the data will be available to use.

Connection API Reference

conn.getStates()

Get the state of all entities. Returns a promise that will resolve to the result of querying the server for all the states.

conn.getServices()

Get all available services. Returns a promise that will resolve to the result of querying the server for all the services.

conn.getConfig()

Get the Home Assistant server config. Returns a promise that will resolve to the result of querying the server for all the config.

conn.callService(domain, service[, serviceData])

Call a service within Home Assistant. Returns a promise that will resolve when the service has been called successfully.

conn.subscribeEvents(eventCallback[, eventType])

Subscribe to all or specific events on the Home Assistant bus. Calls eventCallback for each event that gets received.

Returns a promise that will resolve to a function that will cancel the subscription once called.

conn.addEventListener(eventType, listener)

Listen for events on the connection. See docs.

Using this in NodeJS

To use this package in NodeJS, install the ws package and make it available as WebSocket on the global object before importing this package.

const WebSocket = require("ws");
global.WebSocket = WebSocket;

You'll also need to instantiate your own Auth object.