chatting program with node.js

I am a student who learning develop. So I learning node.js with youtube and blog.
But my program isn’t working(No Server error)

This is my directory

directory image

This is my HTML file

<!DOCTYPE html>
<html lang="ko">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <link rel="stylesheet" href="style.css">
    <title>BSM CHAT</title>
</head>
<body>
    <header id="header">
        <div class="header_logo">
            <a href="./index.html">
                <h1>BSM chat</h1>
                <p>Share some information to each others</p>
            </a>
        </div>
        <div class="header_bar">
            <ul>
                <li><a href="../main.html">INTRO</a></li>
                <li><a href="https://bssm.kro.kr/">BSM</a></li>
                <li><a href="#">로그인</a></li>
                <li><a href="./index.html">채팅</a></li>
                <li><a href="https://github.com/">github</a></li>
            </ul>
        </div>
    </header>
    <br>
    <divS id="section">
        <div class="app__wrap">
            <div id="info" class="app__info"></div>
            <div id="chatWindow" class="app__window"></div>
            <div class="app__input__wrap">
                <input id="chatInput" type="text" class="app__input" autofocus placeholder="대화를 입력해주세요.">
                <button id="chatMessageSendBtn" class="app__button">전송</button>
            </div>
        </div><br>
    </section>
    
    <script src="/js/index.js"></script>
    <script src="/socket.io/socket.io.js"></script>
</body>
</html>

This is my index.js file

'use strict';
let socket = io();

let chatWindow = document.getElementById('chatWindow');
let sendButton = document.getElementById('chatMessageSendBtn');
let chatInput = document.getElementById('chatInput');

socket.on('connect', function(){
    let name = prompt('대화명을 입력해주세요.', '');
    socket.emit('newUserConnect', name);
});

socket.on('updateMessage', function(data){
    if(data.name === 'SERVER'){
        let info = document.getElementById('info');
        info.innerHTML = data.message;

        setTimeout(() => {
            info.innerText = '';
        }, 1000);

    }else{
        let chatMessageEl = drawChatMessage(data);
        chatWindow.appendChild(chatMessageEl);

        chatWindow.scrollTop = chatWindow.scrollHeight;
    }
});

sendButton.addEventListener('click', function(){
    let message = chatInput.value;

    if(!message) return false;
   
    socket.emit('sendMessage', {
        message
    });

    chatInput.value = '';
});

function drawChatMessage(data){
    let wrap = document.createElement('p');
    let message = document.createElement('span');
    let name = document.createElement('span');

    name.innerText = data.name;
    message.innerText = data.message;

    name.classList.add('output__user__name');
    message.classList.add('output__user__message');

    wrap.classList.add('output__user');
    wrap.dataset.id = socket.id;

    wrap.appendChild(name);
    wrap.appendChild(message);

    return wrap;
}

This is my app.js file

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

app.use(cors({
    origin: '*'
}));

app.use(express.static('src'));

app.get('/', function(req, res){
    fs.readFile('./src/index.html', (err, data) => {
        if(err) throw err;

        res.writeHead(200, {
            'Content-Type' : 'text/html'
        })
        .write(data)
        .end();
    });
});

io.sockets.on('connection', function(socket){
    socket.on('newUserConnect', function(name){
        socket.name = name;

        io.sockets.emit('updateMessage', {
            name : 'SERVER',
            message : name + '님이 접속했습니다.'
        });
    });

    socket.on('disconnect', function(){
        io.sockets.emit('updateMessage', {
            name : 'SERVER',
            message : socket.name + '님이 퇴장했습니다.'
        });
    });

    socket.on('sendMessage', function(data){
        data.name = socket.name;
        io.sockets.emit('updateMessage', data);
    });
});

server.listen(8080, function(){
    console.log('서버 실행중...');
});

Chatting is not working
Do you know what is the problem?

I try to fix the code and I
expected working well… but Chatting isn’t working