在 node.js 上使用 socket.io 时如何处理 CORS

我目前正在学习如何使用 Node 创建聊天应用程序并为后端表达并为前端做出反应，但遇到 CORS 错误。

由于 CORS，我在下面收到此错误，但是，我已经在应用程序上实现了所有可以实现的 CORS。

这是错误

:3001/chat?name=jaden&room=love:1 Access to XMLHttpRequest at 'http://localhost:8000/socket.io/?EIO=4&transport=polling&t=NOYd8LK' from origin 'http://127.0.0.1:3001' has been blocked by CORS policy: The 'Access-Control-Allow-Origin' header has a value 'http://localhost:3001' that is not equal to the supplied origin.
polling-xhr.js:203 GET http://localhost:8000/socket.io/?EIO=4&transport=polling&t=NOYd8LK net::ERR_FAILED
create @ polling-xhr.js:203
Request @ polling-xhr.js:120
request @ polling-xhr.js:63
doPoll @ polling-xhr.js:92
poll @ polling.js:76
doOpen @ polling.js:23
open @ transport.js:43
open @ socket.js:170
Socket @ socket.js:94
push../node_modules/component-emitter/index.js.Emitter.emit @ index.js:145
onError @ polling-xhr.js:246
(anonymous) @ polling-xhr.js:196
setTimeout (async)
xhr.onreadystatechange @ polling-xhr.js:195
:3001/chat?name=jaden&room=love:1 Access to XMLHttpRequest at 'http://localhost:8000/socket.io/?EIO=4&transport=polling&t=NOYd9p5' from origin 'http://127.0.0.1:3001' has been blocked by CORS policy: The 'Access-Control-Allow-Origin' header has a value 'http://localhost:3001' that is not equal to the supplied origin.
polling-xhr.js:203 GET http://localhost:8000/socket.io/?EIO=4&transport=polling&t=NOYd9p5 net::ERR_FAILED

这是后端代码

const express = require('express')
const http = require('http')
const socketIo = require('socket.io')
const cors = require('cors')

const app = express()

app.use(cors())

const server = http.createServer(app)

const io = socketIo(server, {
  cors: {
        origin: "http://localhost:3001",
        methods: ["GET", "POST"]
      }
})

// Listening for a connection on the socket.io server

io.on('connection', (socket)=>{
  // the moment i get a connection, i want to send a welcome message
  socket.on('join', ({name, room})=>{
    socket.emit('message', {user:'admin', text:`${name}, You're welcome!`})
    socket.broadcast.emit('message', {user:'admin', text:`${name}, just joined`})
    console.log('welcome message')
  })

  socket.on('sendMessage', (message)=>{
    io.emit('message', {user:'user', text:message})
  })

  socket.on("disconnect", ()=>{
    io.emit('message', {user:'admin', text:`user Just left!`})
  })

})


const port = process.env.PORT || 8000
server.listen(port, ()=> console.log(`Listening on port : ${port}`))