如何解决Mern Stack应用连接失败错误

const mongoose = require('mongoose');

mongoose.connect('mongodb://localhost:27017/mydatabase', {
  useNewUrlParser: true,
  useUnifiedTopology: true
}).then(() => {
  console.log('MongoDB connected');
}).catch(err => {
  console.error('MongoDB connection error:', err);
});

const express = require('express');
const cors = require('cors');
const app = express();

app.use(cors());

app.get('/api/data', (req, res) => {
  res.json({ message: 'Hello from server' });
});

app.listen(5000, () => {
  console.log('Server is running on port 5000');
});

fetch('http://localhost:5000/api/data')
  .then(response => response.json())
  .then(data => console.log(data))
  .catch(error => console.error('Error:', error));