node.js express is not receiving request

I am using express web framework and trying to make an $http request from angularjs. I am passing data to request from client but server is not receiving request for some unknown reasons. Please help.

server.js

var express = require('express');
var app = express();
var http = require('http');
var server = http.createServer(app);
var io = require('socket.io')(server);

var path = require('path');
var fs = require('fs');

app.use(express.static(path.join(__dirname, 'public')));

app.post('/readTfile',function (req,res) {
    console.log('i received a request');
    console.log(req.body);  
});

server.listen(3000);

And angular html

<html>   
   <head>
      <title>File tream 2</title>
        <script type="text/javascript" src="javascripts/angular.js"></script>                   
   </head>

   <body>
      <h2>File tream 2 AngularJS</h2>
        <div ng-app = "mainApp">            
            <div id="readfile" ng-controller = "Ctrl1">                 
                <div>{{myfiledata}}</div> </br></br>
            </div>   
       </div>    
   </body>
 <script> 
var mainApp = angular.module("mainApp",[])

mainApp.controller('Ctrl1', function ($scope, $http) {
        var filename = 'D:\\myapp\\public\\test.txt';       
        var obj = {"filename" : filename};
        $scope.myfiledata = 'result';
        $http({
                url: '/readTfile',
                method: "POST",
                data: JSON.stringify(obj),
                //timeout: canceller.promise,
                headers: {'Content-Type': 'application/json','charset' : 'utf-8'}
                }).success(function(result) {
                console.log(result);
                $scope.myfiledata = 'result';                       
                }).error(function(data, status) {
                console.log(data);
                }); 
});            
</script> 
</html>

On console i am getting undefined for req.body

i received a request

undefined

Please help to solve me this problem.