Empty reply from server error in CURL with node.js, express and mongoDB

I am getting the error "Empty reply from server" In CURL, when I try to run "http://localhost:3000/light"

var express = require('express'),
    values = require('./routes/values');

var app = express();

app.get('/light', values.findAll);

app.listen(3000);
console.log('Listening on port 3000...');

and my values.js is

var mongo = require('mongodb');

var Server = mongo.Server,
    Db = mongo.Db,
    BSON = mongo.BSONPure;

var server = new Server('localhost', 27017, {auto_reconnect: true});
db = new Db('sensordb', server);

db.open(function(err, db) {
    if(!err) {
        console.log("Connected to 'sensordb' database");
        db.collection('values', {safe:true}, function(err, collection) {
            if (err) {
                console.log("The 'values' collection doesn't exist. Creating it with sample data...");
                populateDB();
            }
        });
    }
});

exports.findAll = function(req, res) {
    db.collection('values', function(err, collection) {
        collection.find().toArray(function(err, items) {
            res.send(items);
        });
    });
};

var populateDB = function() {

    var values = [
    {
        value: "10",
        date: "121212",
        time: "1214"
    },
    {
        value:  "12",
        date: "121212",
        time: "1224"
    }];

    db.collection('values', function(err, collection) {
        collection.insert(values, {safe:true}, function(err, result) {});
    });

};

Well basically in the above code, I create a database and if the database is empty, I try to populate it. When I run the server code on my terminal I also get something like:

=  Please ensure that you set the default write concern for the database by setting    =
=   one of the options                                                                 =
=                                                                                      =
=     w: (value of > -1 or the string 'majority'), where < 1 means                     =
=        no write acknowlegement                                                       =
=     journal: true/false, wait for flush to journal before acknowlegement             =
=     fsync: true/false, wait for flush to file system before acknowlegement           =
=                                                                                      =
=  For backward compatibility safe is still supported and                              =
=   allows values of [true | false | {j:true} | {w:n, wtimeout:n} | {fsync:true}]      =
=   the default value is false which means the driver receives does not                =
=   return the information of the success/error of the insert/update/remove            =
=                                                                                      =
=   ex: new Db(new Server('localhost', 27017), {safe:false})                           =
=                                                                                      =
=   http://www.mongodb.org/display/DOCS/getLastError+Command                           =
=                                                                                      =
=  The default of no acknowlegement will change in the very near future                =
=                                                                                      =
=  This message will disappear when the default safe is set on the driver Db           =
========================================================================================

Is the above error causing some problem? If so, what? if not, what is responsible?

Any help would be really appreciated.