private static String receiveFromBackEnd(String url, String json) throws IOException, JSONException {
        StringBuilder str = new StringBuilder();

        HttpClient httpclient = new DefaultHttpClient();
        HttpPost httppost = new HttpPost(url);
        httppost.addHeader(new BasicHeader("Content-Type",
                "application/json"));

        httppost.setEntity(new StringEntity(json));

        HttpResponse response = httpclient.execute(httppost);

        BufferedReader reader = new BufferedReader(new InputStreamReader(
                response.getEntity().getContent()));
        String line;
        while ((line = reader.readLine()) != null) {
            str.append(line);
        }

        return str.toString();
    }