有没有办法只在express服务器上运行socket.io

我的代码如下所示:

const express = require('express');

const app = express();

const io = require('socket.io')(app);

io.on('connection',(socket) =>{
    console.log('a user is connected');
});

app.listen(port, () => {
    console.log('server started');
});

当我运行上述代码时,会出现以下错误:

Error: You are trying to attach socket.io to an express request handler function. Please pass a http.Server instance.

那么,有什么方法可以让我只使用express模块运行socket.io吗?