**免责声明：**类似的主题没有为我的问题提供有效的解决方案！

• 已重新启动MongoDB服务器（发生错误时它仍在运行）
• 在Windows上使用MongoDB服务器作为服务（手动启动）
• 通过MongoDB Shell CLI Package建立连接，方法是在命令提示符中按Enter键建立默认连接（mongodb://127.0.0.1:27017/directConnection=true&serverSelectionTimeoutMS=2000）
• 调用npm安装和npm启动（我的依赖项如下所示）
• 检查MongoDB是否正在运行
• 已通过Windows资源监视器检查端口27017是否已被使用TCP的mongod.exe占用，并且未受防火墙限制
• 已检查我没有使用可能会干扰的VPN或代理连接。
• 然后我打开了我正在收听的http://localhost:3000/（app.listen(3000);）
  但是，我仍然收到以下错误：

const timeoutError = new error_1.MongoServerSelectionError(`Server selection timed out after ${serverSelectionTimeoutMS} ms`, this.description);                                     ^
 
MongoServerSelectionError: connect ECONNREFUSED ::1:27017
    at Timeout._onTimeout (\node_modules\mongodb\lib\sdam\topology.js:330:38)
    at listOnTimeout (node:internal/timers:557:17)
    at processTimers (node:internal/timers:500:7) {
  reason: TopologyDescription {
    type: 'Unknown',
    servers: Map(1) {
      'localhost:27017' => ServerDescription {
        _hostAddress: HostAddress { isIPv6: false, host: 'localhost', port: 27017 },
        address: 'localhost:27017',
        type: 'Unknown',
        hosts: [],
        passives: [],
        arbiters: [],
        tags: {},
        maxWireVersion: 0,
        roundTripTime: -1,
        lastUpdateTime: 536295834,
        lastWriteDate: 0,
        error: MongoNetworkError: connect ECONNREFUSED ::1:27017
            at connectionFailureError (\node_modules\mongodb\lib\cmap\connect.js:293:20)
            at Socket.<anonymous> (\node_modules\mongodb\lib\cmap\connect.js:267:22)
            at Object.onceWrapper (node:events:510:26)
            at Socket.emit (node:events:390:28)
            at emitErrorNT (node:internal/streams/destroy:164:8)
            at emitErrorCloseNT (node:internal/streams/destroy:129:3)
            at processTicksAndRejections (node:internal/process/task_queues:83:21)
      }
    },
    stale: false,
    compatible: true,
    heartbeatFrequencyMS: 10000,
    localThresholdMS: 15,
    logicalSessionTimeoutMinutes: undefined
  }
}

我的相依性：

"dependencies": {
    "ejs": "^3.1.6",
    "express": "^4.17.1",
    "mongodb": "^4.0.1"
  },
  "devDependencies": {
    "nodemon": "^2.0.7"
  }

仅供参考：节点. js v17.0.1

**更新：**这是我的database.js文件

const mongodb = require('mongodb');

const MongoClient = mongodb.MongoClient;

let database;

async function connectToDatabase() {
  const client = await MongoClient.connect('mongodb://localhost:27017');
  database = client.db('file-demo');
}

function getDb() {
  if (!database) {
    throw { message: 'Database not connected!' };
  }
  return database;
}

module.exports = {
  connectToDatabase: connectToDatabase,
  getDb: getDb,
};

这是我的app.js：

const path = require('path');

const express = require('express');

const userRoutes = require('./routes/users');
const db = require('./data/database');

const app = express();

app.set('view engine', 'ejs');
app.set('views', path.join(__dirname, 'views'));

app.use(express.urlencoded({ extended: false }));
app.use(express.static('public'));

app.use(userRoutes);

db.connectToDatabase().then(function () {
  app.listen(3000);
});