Fail with bind Ajax to Socket io. And am I actually need this?

I have trouble with binding AJAX to Socket IO. I make a web chat with registration. After registration client send ajax request to the server and it opens web socket to chatting. And i actually don't know am I actyally do this(I mean can I just open socket without AJAX)

var app = express();
var cors = require('cors')
var server = app.listen(4000);

...

            function WebSocket(server, accessMessage)
            {
                var io = require('socket.io')(server);
                    io.on('connection', (ws) => { // ws  -- web socket
                        var currentroom = room_list[0]; // Global room (like a menu)
                        console.log(accessMessage);

                        for (var i = 0; i <= user_list.length; i++) {

                            if (!user_list[i]) {

                                user_list[i] = {
                                    Id: ws,
                                    name: "",
                                    room: "",
                                    Auth: false,
                                    data: {
                                        ImgHASH: ""
                                    }
                                };
                                //joinroom(ws,currentroom);
                                break;

                            }
                        }
                    }
            }