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Developing web apps with React
We provide React hooks and context providers out of the box. The library can be found on GitHub.
First, install the ux4iot-react library:
npm install ux4iot-react
yarn add ux4iot-react
You initialize the ux4iot React library by wrapping your components with a Ux4iotContext
import {Ux4iotContextProvider} from "ux4iot-react";
function App() {
return (
<div className="App">
<MyView />
There are two modes of operations for the library: Development mode and production mode. The initialization differs between the two modes.


type InitializationOptions = {
onSocketConnectionUpdate?: ConnectionUpdateFunction;
reconnectTimeout?: number;
maxReconnectTimeout?: number;
} & (InitializeDevOptions | InitializeProdOptions);
type InitializeDevOptions = {
adminConnectionString: string;
type InitializeProdOptions = {
ux4iotURL: string;
grantRequestFunction: GrantRequestFunctionType;
event listener on socket connection updates
initial timeout in milliseconds when to reconnect after a session couldn't be established
maximum timeout in milliseconds of the reconnect interval after incrementation
The connection string of ux4iot-server
the websocket url of ux4iot-server
custom function to send grant requests to your custom security backend

Development Mode

const UX4IOT_ADMIN_CONNECTION_STRING = "Endpoint=...SharedAccessKey=...";
const devOptions: InitializeDevOptions = {
<Ux4iotContextProvider options={devOptions}>
You can see a complete example in the tutorial using create-react-app.
The value of the adminConnectionString option can be retrieved via the Azure portal:
You can select either the Primary or the Secondary connection string.
In production mode the admin connection string is used by the Security Backend, but as there is no Security Backend in development mode, the frontend accesses the Admin API on its own. For this reason the frontend requires the admin connection string.

Usage of Development Mode

Under no circumstances should you publish your web application in development mode. It allows anyone with access to the web application to perform any requests towards your IoT devices and it also exposes the admin connection string that must be kept secret.

Production Mode

For production mode you need to provide a security backend for managing access permissions. You also need a Grant Request Function that acts as an adapter between the ux4iot library and this backend.
const UX4IOT_WEBSOCKET_URL 'https://ux4iot-xxx.westeurope.azurecontainer.io';
const prodOptions: InitializeProdOptions = {
grantRequestFunction: customGrantRequestFunction
<Ux4iotContextProvider options={prodOptions}>
The value for the ux4iotURL parameter is available on your ux4iot instance in the Azure portal:
For detailed information on how to implement the Grant Request Function, see the dedicated chapter.

reconnectTimeout & maxReconnectTimeout

When you render a Ux4iotContextProvider, it tries to establish a session by calling the /session endpoint of ux4iot. If this request fails, it will retry again after the milliseconds defined in reconnectTimeout. If the retry fails it will double the timeout and retry again after the doubled timeout or maxReconnectTimeout if maxReconnectTimeout is larger.

Example reconnectTimeout = 5000, maxReconnectTimeout = 50000

Ux4iot fails to connect to ux4iot and fails. Retries afterwards at 5, 10, 20, 40, 50, 50, 50,... seconds
Retries will not stop retrying until the session is established. The defaults are reconnectTimeout = 5000, maxReconnectTimeout = 30000


In both Development and Production mode you can pass a function to the options of the Ux4iotContextProvider
const devOptions: InitializeDevOptions = {
onSocketConnectionUpdate: (reason, description) => { /* handle update */ }
const prodOptions: InitializeProdOptions = {
grantRequestFunction: customGrantRequestFunction
onSocketConnectionUpdate: (reason, description) => { /* handle update */ }
It takes two arguments:
  • reason - can be one of four strings:
    • socket_connect - called when the socket is established with the server
    • socket_connect_error called when the client throws an error when establishing the socket
    • socket_disconnect - called when the socket is disconnected
    • ux4iot_unreachable - called when a sessionId cannot be fetched from the ux4iot instance
    Every reason except for ux4iot_unreachable originates from socket.io and is documented here: https://socket.io/docs/v4/client-api/#event-connect
  • description - string | undefined : error explanation provided in socket_connect_error, socket_disconnect and ux4iot_unreachable
The full function type you need to provide is
export type ConnectionUpdateReason =
| 'socket_connect'
| 'socket_connect_error'
| 'socket_disconnect'
| 'ux4iot_unreachable';
export type ConnectionUpdateFunction = (
reason: ConnectionUpdateReason,
description?: string
) => void;