Connecting to mongodb

Code:

     var Db = require('mongodb').Db,
        Server = require('mongodb').Server,
        Client = new Db('test', new Server('127.0.0.1', 52235, {}))

In Function: ...

     Client.open(function(err, pClient) {
        Client.collection('test_insert', function(err, collection){
            collection.find().toArray(function(err, results) {
                console.log(results);
            });
        });
        // etc.
     });

This shows error: Cannot read property 'arbiterOnly' of undefined can you help me?