我使用以下示例代码从NodeJS连接到MongoDB时遇到问题。我试着运行“mongod”，有或没有sudo，但nodejs代码仍然无法连接。我可以使用“mongo”成功连接到数据库。
运行时间：Mac OS 10.6.8

var mongoClient = require('mongodb').MongoClient;
   mongoClient.connect("mongodb://localhost:27017/test", function(error, db) {
        if(!error){
             console.log("We are connected");
        }
        else
           console.dir(error);
    });

运行上述代码时出现以下错误：[错误：无法连接到[localhost：27017]]
也尝试了mongoose，但类似的错误：

var mongoose = require('mongoose');
    mongoose.connect('mongodb://localhost/test');
    var db = mongoose.connection;
    db.on('error', console.error.bind(console, 'connection error:'));
    db.once('open', function callback () {
          console.log("DB connected");
    // yay!
    });

输出：连接错误：[错误：无法连接到[localhost：27017]]
这是mongod的日志

mongod --help for help and startup options
2014-07-11T23:33:47.843-0700 kern.sched unavailable
2014-07-11T23:33:47.849-0700 [initandlisten] MongoDB starting : pid=29942 port=27017 dbpath=/data/db 64-bit host=usc8bcc8a0d0b1
2014-07-11T23:33:47.849-0700 [initandlisten]
2014-07-11T23:33:47.849-0700 [initandlisten] ** WARNING: soft rlimits too low. Number of files is 256, should be at least 1000
2014-07-11T23:33:47.849-0700 [initandlisten] db version v2.6.3
2014-07-11T23:33:47.849-0700 [initandlisten] git version: nogitversion
2014-07-11T23:33:47.849-0700 [initandlisten] build info: Darwin usc8bcc8a0d0b1 10.8.0 Darwin Kernel Version 10.8.0: Tue Jun  7 16:33:36 PDT 2011; root:xnu-1504.15.3~1/RELEASE_I386 i386 BOOST_LIB_VERSION=1_49
2014-07-11T23:33:47.849-0700 [initandlisten] allocator: system
2014-07-11T23:33:47.849-0700 [initandlisten] options: {}
2014-07-11T23:33:47.850-0700 [initandlisten] journal dir=/data/db/journal
2014-07-11T23:33:47.850-0700 [initandlisten] recover : no journal files present, no recovery needed
2014-07-11T23:33:47.901-0700 [initandlisten] waiting for connections on port 27017
2014-07-11T23:34:47.901-0700 [clientcursormon] mem (MB) res:48 virt:2810
2014-07-11T23:34:47.901-0700 [clientcursormon]  mapped (incl journal view):320
2014-07-11T23:34:47.901-0700 [clientcursormon]  connections:0