Logging into Splunk SDK gives 404 error

I'm trying the basic examples using the Javascript Splunk SDK using Node 0.8.0.

Trying to login to Splunk through the API gives me a 404 error.

My Javascript code -

username = "admin";
password = "changeme";
scheme   = "https";
host     = "localhost";
port     = "8089";
version  = "5.0";

Async = splunkjs.Async;
utils = splunkjs.Utils;

var tag = null;

done = callback = function() {
    $(tag).remove();
};

var http = new splunkjs.ProxyHttp("/proxy");
var service = new splunkjs.Service(http, {
    username: username,
    password: password,
    scheme: scheme,
    host: host,
    port: port,
    version: version
});

Async.chain([
        // First, we log in
        function(done) {
            service.login(done);
        },
        // Retrieve the apps
        function(success, done) {
            if (!success) {
                done("Error logging in");
            }

            service.apps().fetch(done);
        },
        // Print them out
        function(apps, done) {     
            var appsList = apps.list();       
            console.log("Applications:");
            for(var i = 0; i < appsList.length; i++) {
                var app = appsList[i];
                console.log("  App " + i + ": " + app.name);
            } 
            done();
        }
    ],
    function(err) {
        callback(err);        
    }
);

This is in my own code. The same script works when run from the SDK examples. What am I doing wrong?

EDIT - My backend is running in Node.JS so I'm confused as to whether I have to change some config files or not.