Javascript 404在角度和节点中使用socket.io时出错

我正在使用socket.io制作一个MEAN应用程序。我通过我的节点发送一个事件，该事件在我的index.js文件中定义，该文件包含在我的app.js中。我在运行angular应用程序时遇到404错误

let  express = require('express');
let router = express.Router();
let server = require('http').Server(express);
let io = require('socket.io')(server);


/* GET home page. */
router.get('/', function(req, res, next) {
   res.render('index', { title: 'Express' });
});


io.on('connection', (socket) => {
   console.log('User connected');
   socket.emit('hello',{
      greeting: 'Hello agam'
   });
});
module.exports = router;

包含socket.io和调用节点服务器的代码

import { Component, OnInit } from '@angular/core';
import * as socketIo from 'socket.io-client';
@Component({
  selector: 'app-home-component',
  templateUrl: './home-component.component.html',
  styleUrls: ['./home-component.component.css']
})
export class HomeComponentComponent implements OnInit {
  constructor() {

   }

  ngOnInit() {
    const socket = socketIo('http://localhost:3000');
    socket.on('hello', (data) => {
    console.log(data);
    });
  }

 }

运行应用程序时出现的错误：

zone.js:2935 GET http://localhost:3000/socket.io/?
EIO=3&transport=polling&t=M4aQ8Fg 404 (Not Found)

这是我的app.js：

var express = require('express');
var path = require('path');
var logger = require('morgan');
var cookieParser = require('cookie-parser');
var bodyParser = require('body-parser');
var cors = require('cors');

var index = require('./routes/index');
var users = require('./routes/users');

var app = express();



app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'ejs');

app.use(cors({origin: true, credentials: true}));

app.use(logger('dev'));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false }));
app.use(cookieParser());
app.use(express.static(path.join(__dirname, 'public')));

app.use('/', index);
app.use('/users', users);

app.use(function(req, res, next) {
var err = new Error('Not Found');
 err.status = 404;
  next(err);
});

app.use(function(err, req, res, next) {
 res.locals.message = err.message;
 res.locals.error = req.app.get('env') === 'development' ? err : {};

 res.status(err.status || 500);
 res.render('error');
});

module.exports = app;

加：

---

请粘贴您的代码，而不是图片，否则问题将被否决！这也适用于错误消息…抱歉。就这么做了。必须发布错误的详细屏幕截图。请帮助问题似乎在您的express服务器中。。。你们能把代码粘贴到路由器所在的地方吗？就是这么做的。请看一看，我在任何地方都看不到你在做

listen（）。您还将express传递到
.Server（）
，而不调用它。
var app = require('express')();
var http = require('http').Server(app);
var io = require('socket.io')(http);

...
  // And at end of file
  http.listen(3000, () => {
    console.log('started on port 3000');
  });