请问koa2如何实现socket.io？

[l20]

我代码是这样的：

const Koa = require('koa');
const app = new Koa();
const server = require('http').Server(app.callback());
const io = require('socket.io')(server);

io.on('connection', function(socket){
  io.emit('this', { will: 'be received by everyone'});

  socket.on('private message', function (from, msg) {
    console.log('I received a private message by ', from, ' saying：', msg);
  });

  socket.on('disconnect', function () {
    io.emit('user disconnected');
  });

});

但是前端请求的时候找不到数据，该如何做呢，希望提供ko2的一些源码。

[lensh]

const server = require('http').Server(app.callback());
改成
const server = require('http').createServer(app.callback());

[l20]

@lensh 还是不行啊，浏览器打印这要的错误,是什么原因请求不到呢？

socket.io.js:2 XHR finished loading: GET "http://localhost:3001/socket.io/?EIO=3&transport=polling&t=LwZ9ZPG".
i.create @ socket.io.js:2
i @ socket.io.js:2
o.request @ socket.io.js:2
o.doPoll @ socket.io.js:2
r.poll @ socket.io.js:2
r.doOpen @ socket.io.js:2
r.open @ socket.io.js:2
r.open @ socket.io.js:1
r @ socket.io.js:1
r @ socket.io.js:1
r.open.r.connect @ socket.io.js:1
(anonymous) @ socket.io.js:1
socket.io.js:2 GET http://localhost:3001/socket.io/?EIO=3&transport=polling&t=LwZ9ae6 404 (Not Found)
i.create @ socket.io.js:2
i @ socket.io.js:2
o.request @ socket.io.js:2
o.doPoll @ socket.io.js:2
r.poll @ socket.io.js:2
r.doOpen @ socket.io.js:2
r.open @ socket.io.js:2
r.open @ socket.io.js:1
r @ socket.io.js:1
r @ socket.io.js:1
r.open.r.connect @ socket.io.js:1
(anonymous) @ socket.io.js:1
socket.io.js:2 XHR finished loading: GET "http://localhost:3001/socket.io/?EIO=3&transport=polling&t=LwZ9ae6".

[lensh]

404不是已经很明显了吗？你看看端口是否一致，看服务端的代码是不是监听的3001端口。。。实在不行的话，你提供一下你项目的github地址吧，我再帮你看看。。。

[l20]

@lensh 感谢回答，是其他问题，错误找到了。

[harry-code]

同样遇到，请问大佬是怎么解决的呢？