When refreshing the page, io.on('connection') is fired multiple times. Why?

Question

Socket.io

const models = require('../models/models.js');
const path = require('path');
let user = false;




module.exports = function (app,passport,io, req, res) {
    let users={};
    let keys={};


    io.on('connection', function(socket){
        user = req.user;

        console.log('Пользователь ' + user.email + ' подключился!');

        users[user.email] = socket.id;
        keys[socket.id] = user.email;

        //Отлючение пользователя
        socket.on('disconnect', function(){
            console.log('Отлючение ' + user.email);
            delete users[keys[socket.id]];
            delete keys[socket.id];
        });
    });

};

That is, when I open the page, I see in the console:

The user user has connected!

When refreshing the page:

disable user

The user user has connected!
The user user has connected!

When you re-update 2 shutdowns, 3 connections,
then 3 disconnections 4 connections. and so on
. I connected the controller in which I have io.connect like this:

app.get('/chat', isLoggedIn, function(req, res) {
        require('./controller/controller.js')(app,passport,io, req, res);
        res.render('chat.ejs');
    });

Why does socket.io call connect callback multiple times after page reload?
Here is the same. But there is no answer

Answer 1

Each time a connection is made, a new disconnect listener is created.
At a minimum, it must be pulled out of on('connection').
On the client, it is similar to check that there are no on () in others.
And of course, connecting the module with each request adds event listening every time.
Very strange code, why everything is mixed together and the socket server and the normal server.
Take out the socket server separately. On the route, only give the layout with scripts.