Titanium Appcelerator API call error - HTTP ERROR

I am having a website which contains login page. When user tries to log in using username and password. Data is being passed in Form Data. Please have a look as following image to get idea.

Now I want to use the same api in my Titanium application and get all details or logged in user which i am performing using below mentioned code.

var url= "http://ift.tt/1Ntcdbe";
 var jsonData = {
    username: "admin",
    password: "password1"
 };
 var xhr = Ti.Network.createHTTPClient();
 xhr.onload = function(e) {
    var obj = JSON.parse(this.responseText);
    alert("DATA IS " + JSON.stringify(obj));
 };
 xhr.onerror = function(e) {
    Ti.API.info("ERROR " + e.error);
 };
 xhr.onsendstream = function(e){
    Ti.API.info("onsendstream");
 };
 xhr.ondatastream = function(e){
    Ti.API.info("ondatastream");
 };
 xhr.open('POST',url);
 xhr.send(JSON.stringify(jsonData));

I am getting HTTP error. I even tried setting xhr.setHeader('Content-Type','application/json') as well as verified url its same as that is being used by website. Can any one help me out with this ? Or is there any way in order to make sure that titanium code passes data in form-data ? Or any suggestion regarding this would be of great help.