Node.js [错误：无法连接到[localhost:27017]]。此错误发生在mongodb上

我的示例代码在这里。我正在从《开发_backbone.js_应用程序》一书中学习 我已经在我的电脑上安装了mongodb。我在这个网站上搜索了它的答案，但没有任何线索。 有人有什么解决办法吗？谢谢

// Module dependencies.
var application_root = __dirname,
    express = require('express'), //Web framework
    path = require('path'), //Utilities for dealing with file paths
    mongoose = require('mongoose'); //MongoDB integration
//Create server
var app = express();
// Configure server
app.configure(function () {
    //parses request body and populates request.body
    app.use(express.bodyParser());
    //checks request.body for HTTP method overrides
    app.use(express.methodOverride());
    //perform route lookup based on URL and HTTP method
    app.use(app.router);
    //Where to serve static content
    app.use(express.static(path.join(application_root, 'site')));
    //Show all errors in development
    app.use(express.errorHandler({
        dumpExceptions: true,
        showStack: true
    }));
});


//Start server
var port =4711;
app.listen(port, function () {
    console.log('Express server listening on port %d in %s mode',
        port, app.settings.env);
});

// Routes
app.get( '/api', function( request, response ) {

    response.send( 'Library API is running and the requestis' );
});

//Connect to database
mongoose.connect( 'mongodb://localhost/library_database', function(err) { if (err) console.log(err); } );
//Schemas
var Book = new mongoose.Schema({
    title: String,
    author: String,
    releaseDate: Date
});
//Models
var BookModel = mongoose.model( 'Book', Book );

//Get a list of all books
app.get( '/api/books', function( request, response ) {
    return BookModel.find( function( err, books ) {
        if( !err ) {
            return response.send( books );
        } else {
            return console.log( err );
        }
    });
});

---

您是否已在本地安装并运行mongodb？？

---

在运行mongo的情况下，保持终端选项卡或窗口处于打开状态。

当您在计算机上使用本地数据库时，必须执行mongod（可以在下载并解压缩的mongodb的bin文件夹中找到）。

这是windows还是linux？PC？Windows Linux还是Mac？您是如何运行它的？Windows 8操作系统作为服务运行的？还是你刚安装的？如果未作为服务安装并启动该服务，则需要在命令行窗口中运行。我在命令行窗口中运行它，在上面显示的server.js文件所在的目录中使用命令“node server.js”