Create separate rooms based on Pin code in the URL in socket io

I'm new in node js and socket io, I'm trying to create interactive quizzes based on pin code given in the url for ex: http://domain/start/5555 should create a quiz page with name 5555 and when clients have the pin code they can connect to this quiz. So it means i have to have a quiz page which shows all connected clients for example but i have some prblems with io.sockets.in(pincode).emit() because i don't know if i'm creating rooms correctly or not! here is my code

Client.js

var socket = io();
socket.on('connect', function () {
    var params = jQuery.deparam(window.location.search);// To get the name and the room
    socket.emit('join', params, function (err) {
        if (err) {
            alert(err);
            window.location.href = '/join.html';
        } else {
            console.log('No error');
        }
    });
});

Server.js

app.get('/start/:pincode', (req, res) => {
io.on('connection', (socket) => { // to rigester connection listener
    console.log('New user is connected');
    // When somebody connects it verifies if the name and the room are valid strings
    socket.on('join', (params, callback) => {
        if (!isRealSrting(params.name) || !isRealSrting(params.pincode)) {
            return callback('Name and pincode are required');
        }
        socket.join(params.pincode);
        users.removeUser(socket.id);//Remove the user from other places
        users.addUser(socket.id, params.name, params.pincode);
        var x = users.getUserList(params.pincode);
        console.log(x);
        io.sockets.in(params.pincode).emit('updateUserList', { //here it doesn't work i don't know why!
            users: users.getUserList(params.pincode),
            pincode: params.pincode
        });
        socket.emit('newMessage', {
            user: params.name,
            pincode: params.pincode,
            readyMessage: 'You are connected'
        });// when the user connect to the server he gets this message
        callback();
    });
    socket.on('disconnect', () => {
        var user = users.removeUser(socket.id);
        if (user) {
            io.emit('updateUserList', users.getUserList(user.pincode));
            //io.to(user.room).emit('newMessage', generateMessage('Admin', `${user.name} has left`));
        }
    });
});
res.render('start.hbs', {
    pincode: req.params.pincode
});
});

and the main page Start.js

var socket = io();
var pincode;
socket.on('updateUserList', function (users) {
   console.log('here');
   var ol = jQuery('<ol></ol>');
   var usercount = users.users.length; // Players number
   pincode = users.pincode;    
});

Any help or suggestion please?