使用socket.io（NodeJs）检测客户端是否与网络断开连接

Question

I am creating an app with node.js and socket.io. I need to detect if client side is disconnected from internet and fire socket.disconnect() manually/automatically.

I have searched but cant find any solution. Here is my client and server side code.

const app = require('express')();
const server = require('http').Server(app);
const io = require('socket.io')(server);
const fs = require('fs');

server.listen(8005, () => console.log('app is running at 8005 port'));

app.get('/', (req, res) => {
    res.sendFile(__dirname + '/index.html');
})

const sockets = {};
io.sockets.on('connection', (socket) => {
    socket.once('disconnect', function () {
        console.log('-------disconencted', socket.userId); 
        delete sockets[socket.userId];
    });
    socket.on('init', (data) => {
        socket.userId = data.userId;
        sockets[data.userId] = socket;
        sockets[data.userId].emit('userOnline', { id : data.userId});
        console.log(socket.userId,'--------useronline-----------',data)
    });


    socket.on('test', (data) => {
        socket.emit('testResp', { id : 'sdfd'});
        console.log('--------useronline-----------',socket.userId);
    });

    socket.on('total', data => {
        socket.emit('totalResp', { users: Object.keys(sockets)})
        console.log('--------total-----------',socket.userId);

    })





})

Client side code:

var socket = io('http://localhost:8005');
    socket.on('userOnline', function (data) {
        console.log(socket.userId, '---userOnline--------', data);
    });

    socket.on('testResp', function (data) {
        console.log(socket.userId, '----testResp-------', data);
    });

    socket.on('totalResp', function (data) {
        document.querySelector('#total_users_length').innerHTML = data.users.length;

        console.log(socket.userId, '----totalResp-------', data);
    });
    document.querySelector('#init').addEventListener('click', function(){

        socket.emit('init', {userId: document.querySelector('input').value});
    });

    document.querySelector('#test').addEventListener('click', function(){

      socket.emit('test', {test: 'tst'});
    });

    document.querySelector('#total').addEventListener('click', function(){

    socket.emit('total', {test: 'tst'});
    });

I am storing the userId of user in socket so that when a user disconnected with server, i can find its id and can send notifications. Thanks in advance.

Answer 1

I think you are looking for the disconnect event, You can try with this.

socket.on('disconnect', function () {
    io.emit('user disconnected');
  });
});

Since you have already added this in your code. socket fires the disconnect event whenever the client is not responding to the heartbeat that socket implements internally. You can check the docs for more info Socket.io check the "Disconnection detection" section.