我对MERN和React有点陌生，到目前为止，服务器端口一直在工作，直到我尝试连接到Mongodb。

require('dotenv').config()

const express = require("express")
const mongoose = require('mongoose')
const workoutRoutes = require('./routes/workouts')

const app = express()

//middleware
app.use(express.json())

app.use((req, res, next) => {
    console.log(req.path, req.method)
    next()
})

//routes
app.use('/api/workouts', workoutRoutes)

//connect to db
mongoose.connect(process.env.MONGO_URI)
  .then(() => {
    // listen to port
    app.listen(process.env.PORT, () => {
      console.log('listening for requests on port', process.env.PORT)
    })
  })
  .catch((err) => {
    console.log(err)
  }) 

//listening for requests
app.listen(process.env.PORT, () => {
    console.log("listening on port", process.env.PORT)
})

我得到这个错误

Error: listen EADDRINUSE: address already in use :::4000
    at Server.setupListenHandle [as _listen2] (node:net:1733:16)
    at listenInCluster (node:net:1781:12)
    at Server.listen (node:net:1869:7)
    at Function.listen (C:\Users\urbai\OneDrive\Desktop\MERN STACK\backend\node_modules\express\lib\application.js:635:24)
    at C:\Users\urbai\OneDrive\Desktop\MERN STACK\backend\server.js:25:9
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
Emitted 'error' event on Server instance at:
    at emitErrorNT (node:net:1760:8)
    at process.processTicksAndRejections (node:internal/process/task_queues:82:21) {
  code: 'EADDRINUSE',
  errno: -4091,
  syscall: 'listen',
  address: '::',
  port: 4000
}

Node.js v18.13.0
[nodemon] app crashed - waiting for file changes before starting...

我多次尝试更改端口，关闭任务管理器中的打开节点任务，但仍然存在相同的问题