Instagram API not working via Nodejs

Here is my http POST code, running on localhost:

if(headers['Content-Type'] == undefined)
        headers['Content-Type'] = 'application/x-www-form-urlencoded';

    var post_options = {
          host: host,
          path: path,
          port: port,
          method: 'POST',
          headers: headers
    };

    if(headers['Content-Type'] == "application/json"){
        post_options["json"] = true;
        var post_data = JSON.stringify(body);
    }else
        var post_data = querystring.stringify(body);

     var post_req = http.request(post_options, function(res) {

          var body = '';

          console.log("INSIDE CALLBACK HTTP POST");

          res.setEncoding('utf8');

          res.on('data', function (chunk) {
              body += chunk;
              console.log('Response: ' + chunk);
          });

          res.on('end', function () {
            var post = querystring.parse(body);
            console.log("FINAL BODY:",post);
          });

          //console.log("RESPONSE in http POST:",res);

      });

      // post the data
      console.log("WRITING HTTP POST DATA");
      var sent_handler = post_req.write(post_data);

      console.log("POST_REQ:",post_req);
      console.log("sent_handler:",sent_handler);

      post_req.end();

Here is the information I send to instagram exactly:

host = "api.instagram.com"
path = "/oauth/access_token"
body as follows:

body["client_id"] = CLIENT_ID;

body["client_secret"] = CLIENT_SECRET;

body["grant_type"] = "authorization_code";

body["redirect_uri"] = AUTHORIZATION_REDIRECT_URI;

body["code"] = login_code;

body["scope"] = "public_content";
headers = {} (empty, assumes headers['Content-Type'] == undefined as true)
Important: sent_handler returns false
The console.log for "FINAL BODY" (variable post) returns "{}"