React Native useWebSocket

React Hook designed to provide robust WebSocket integrations to your React Native project.

Credit (fork from): robtaussig/react-use-websocket

Example Implementation

``js
import * as React from "react";
import useWebSocket, { ReadyState } from "../../src";
import { Button, Text, FlatList } from "react-native";

export default function App() {

const [socketUrl] = React.useState("wss://echo.websocket.org");

const messageHistory = React.useRef < any > [];

const { sendMessage, lastMessage, readyState } = useWebSocket(socketUrl);

messageHistory.current = React.useMemo(
() => messageHistory.current.concat(lastMessage),
[lastMessage]
);

const sendM = () => sendMessage("Hello");

const handleClickSendMessage = React.useCallback(sendM, [sendM]);

const connectionStatus = {
[ReadyState.CONNECTING]: "Connecting",
[ReadyState.OPEN]: "Open",
[ReadyState.CLOSING]: "Closing",
[ReadyState.CLOSED]: "Closed",
[ReadyState.UNINSTANTIATED]: "Uninstantiated",
}[readyState];

return (
<>
onPress={handleClickSendMessage}
disabled={readyState !== ReadyState.OPEN}
title={"Click Me to send 'Hello'"}
/>
The WebSocket is currently {connectionStatus}
{lastMessage ? Last message: {lastMessage.data} : null}
keyExtractor={(item, i) => {
return i.toString();
}}
data={messageHistory.current}
renderItem={({ item }) =>
item && item.message && {item.message.data}
}
/>

);
}

`



From the example above, the component will rerender every time the readyState of the WebSocket changes, as well as when the WebSocket receives a message (which will change lastMessage). sendMessage is a memoized callback that will pass the message to the current WebSocket (referenced to internally with useRef).

Features

- Handles reconnect logic

- Multiple components can (optionally) use a single WebSocket, which is closed and cleaned up when all subscribed components have unsubscribed/unmounted

- Written in TypeScript

- Socket.io support

- No more waiting for the WebSocket to open before messages can be sent. Pre-connection messages are queued up and sent on connection

- Provides direct access to unshared WebSockets, while proxying shared WebSockets. Proxied WebSockets provide subscribers controlled access to the underlying (shared) WebSocket, without allowing unsafe behavior

Getting Started

`sh
npm install react-native-use-websocket
`



`js
import useWebSocket from 'react-native-use-websocket';

// In functional React component
// This can also be an async getter function. See notes below on Async Urls.

const socketUrl = 'wss://echo.websocket.org';
const {
sendMessage,
sendJsonMessage,
lastMessage,
lastJsonMessage,
readyState,
getWebSocket
} = useWebSocket(socketUrl, {
onOpen: () => console.log('opened'),
//Will attempt to reconnect on all close events, such as server shutting down
shouldReconnect: (closeEvent) => true,
});
`

Requirements

- React 16.8+

- Cannot be used within a class component (must be a functional component that supports React Hooks)

Async Urls

Instead of passing a string as the first argument to useWebSocket, you can pass a function that returns a string (or a promise that resolves to a string). It's important to note, however, that other rules still apply -- namely, that if the function reference changes, then it will be called again, potentially instantiating a new WebSocket if the returned url changes.



`js
import useWebSocket from 'react-use-websocket';

// In functional React component

const getSocketUrl = useCallback(() => {
return new Promise(resolve => {
setTimeout(() => {
resolve('wss://echo.websocket.org');
}, 2000);
});
}, []);

const {
sendMessage,
lastMessage,
readyState,
getWebSocket
} = useWebSocket(getSocketUrl, STATIC_OPTIONS);
`

API

$3

`ts
type sendMessage = (message: string) => void;
`

The argument sent through sendMessage will be passed directly to WebSocket#send. sendMessage will be static, and thus can be passed down through children components without triggering prop changes. Messages sent before the WebSocket is open will be queued up and sent on connection.

$3

`ts
type sendJsonMessage = (message: any) => void;
`

Message will first be passed through JSON.stringify.

$3

`ts
type lastMessage = WebSocketEventMap['message'];
`

Will be an unparsed MessageEvent received from the WebSocket.

$3

`ts
type lastMessage = any;
`

A JSON.parsed object from the lastMessage. If lastMessage is not a valid JSON string, lastJsonMessage will be an empty object.

$3

`ts
enum ReadyState {
UNINSTANTIATED = -1,
CONNECTING = 0,
OPEN = 1,
CLOSING = 2,
CLOSED = 3
}
`

Will be an integer representing the readyState of the WebSocket. -1 is not a valid WebSocket readyState, but instead indicates that the WebSocket has not been instantiated yet (either because the url is null or connect param is false)

$3

`ts
type getWebSocket = () => WebSocket | Proxy
`

If the WebSocket is shared, calling this function will lazily instantiate a Proxy instance that wraps the underlying WebSocket. You can get and set properties on the return value that will directly interact with the WebSocket, however certain properties/methods are protected (cannot invoke close or send, and cannot redefine any of the event handlers like onmessage, onclose, onopen and onerror. An example of using this:



`js
const {
sendMessage,
lastMessage,
readyState,
getWebSocket
} = useWebSocket('wss://echo.websocket.org', {
share: true
});

useEffect(() => {

console.log(getWebSocket().binaryType) //=> 'blob'

//Change binaryType property of WebSocket
getWebSocket().binaryType = 'arraybuffer';
console.log(getWebSocket().binaryType) //=> 'arraybuffer'

//Attempt to change event handler
getWebSocket().onmessage = console.log //=> A warning is logged to console: 'The WebSocket's event handlers should be defined through the options object passed into useWebSocket.'

//Attempt to change an immutable property
getWebSocket().url = 'www.google.com';
console.log(getWebSocket().url); //=> 'wss://echo.websocket.org'

//Attempt to call webSocket#send
getWebSocket().send('Hello from WebSocket'); //=> No message is sent, and no error thrown (a no-op function was returned), but an error will be logged to console: 'Calling methods directly on the WebSocket is not supported at this moment. You must use the methods returned by useWebSocket.'

}, []);
`

If the WebSocket is not shared (via options), then the return value is the underlying WebSocket, and thus methods such as close and send can be accessed and used.

Reconnecting

By default, useWebSocket will not attempt to reconnect to a WebSocket. This behavior can be modified through a few options. To attempt to reconnect on error events, set Options#retryOnError to true. Because CloseEvents are less straight forward (e.g., was it triggered intentionally by the client or by something unexpected by the server restarting?), Options#shouldReconnect must be provided as a callback, with the socket CloseEvent as the first and only argument, and a return value of either true or false. If true, useWebSocket will attempt to reconnect up to a specified number of attempts (with a default of 20) at a specified interval (with a default of 5000 (ms)). The option properties for attempts is Options#reconnectAttempts and the interval is Options#reconnectInterval. As an example:



`js
const didUnmount = useRef(false);

const [sendMessage, lastMessage, readyState] = useWebSocket(
'wss://echo.websocket.org', {
shouldReconnect: (closeEvent) => {

/*
useWebSocket will handle unmounting for you, but this is an example of a
case in which you would not want it to automatically reconnect
*/
return didUnmount.current === false;
},
reconnectAttempts: 10,
reconnectInterval: 3000,
});

useEffect(() => {
return () => {
didUnmount.current = true;
};
}, []);
`

Options

`ts
interface Options {
share ? : boolean;
shouldReconnect ? : (event: WebSocketEventMap['close']) => boolean;
reconnectInterval ? : number;
reconnectAttempts ? : number;
filter ? : (message: WebSocketEventMap['message']) => boolean;
retryOnError ? : boolean;
onOpen ? : (event: WebSocketEventMap['open']) => void;
onClose ? : (event: WebSocketEventMap['close']) => void;
onMessage ? : (event: WebSocketEventMap['message']) => void;
onError ? : (event: WebSocketEventMap['error']) => void;
onReconnectStop?: (numAttempts: number) => void;
fromSocketIO ? : boolean;
queryParams ? : {
[key: string]: string | number;
};
protocols ? : string | string[];
options ? : {
[optionName: string]: any;
headers: {
[headerName: string]: string;
};
} | null;
}
`

$3

See section on Reconnecting.

$3

Number of milliseconds to wait until it attempts to reconnect. Default is 5000.

$3

Each of Options#onMessage, Options#onError, Options#onClose, and Options#onOpen will be called on the corresponding WebSocket event, if provided. Each will be passed the same event provided from the WebSocket.

$3

If provided in options, will be called when websocket exceeds reconnect limit, either as provided in the options or the default value of 20.

$3

If set to true, a new WebSocket will not be instantiated if one for the same url has already been created for another component. Once all subscribing components have either unmounted or changed their target socket url, shared WebSockets will be closed and cleaned up. No other APIs should be affected by this.

$3

SocketIO acts as a layer on top of the WebSocket protocol, and the required client-side implementation involves a few peculiarities. If you have a SocketIO back-end, or are converting a client-side application that uses the socketIO library, setting this to true might be enough to allow useWebSocket to work interchangeably. This is an experimental option as the SocketIO library might change its API at any time. This was tested with Socket IO 2.1.1.

$3

Pass an object representing an arbitrary number of query parameters, which will be converted into stringified query params and appended to the WebSocket url.



`js
const queryParams = {
'user_id': 1,
'room_id': 5
};

//?user_id=1&room_id=5
`

$3

SocketIO sends messages in a format that isn't JSON-parsable. One example is:

`
"42["Action",{"key":"value"}]"
`

An extension of this hook is available by importing useSocketIO:

`js
import { useSocketIO } from 'react-use-websocket';

//Same API in component
const {
sendMessage,
lastMessage,
readyState
} = useSocketIO('socket.io');
`

It is important to note that lastMessage will not be a MessageEvent, but instead an object with two keys: type and payload.

$3

If a function is provided with the key filter, incoming messages will be passed through the function, and only if it returns true will the hook pass along the lastMessage` and update your component.