socket..io
<script src="https://cdn.socket.io/socket.io-3.0.1.min.js"></script>socket..io
<script src="https://cdn.socket.io/socket.io-3.0.1.min.js"></script>js socket.emit
const socket = io('ws://localhost:3000');
socket.on('connect', () => {
// either with send()
socket.send('Hello!');
// or with emit() and custom event names
socket.emit('salutations', 'Hello!', { 'mr': 'john' }, Uint8Array.from([1, 2, 3, 4]));});
// handle the event sent with socket.send()
socket.on('message', data => {
console.log(data);
});
// handle the event sent with socket.emit()
socket.on('greetings', (elem1, elem2, elem3) => {
console.log(elem1, elem2, elem3);
});how to check whether the user is online or not using socket.io
const users = {};
io.on('connection', function(socket){
console.log('a user connected');
socket.on('login', function(data){
console.log('a user ' + data.userId + ' connected');
// saving userId to array with socket ID
users[socket.id] = data.userId;
});
socket.on('disconnect', function(){
console.log('user ' + users[socket.id] + ' disconnected');
// remove saved socket from users object
delete users[socket.id];
});
});socket.io
$ npm install socket.iosocket io express
const app = require("express")();const httpServer = require("http").createServer(app);const options = { /* ... */ };const io = require("socket.io")(httpServer, options);io.on("connection", socket => { /* ... */ });httpServer.listen(3000);// WARNING !!! app.listen(3000); will not work here, as it creates a new HTTP serverCopyright © 2021 Codeinu
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