private static String receiveFromHttpBackEnd(String url, String json) throws IOException, JSONException {
        URL obj = new URL(url);
        HttpURLConnection con = (HttpURLConnection) obj.openConnection();

        String USER_AGENT = "Mozilla/5.0";
        //add reuqest header
        con.setRequestMethod("POST");
        con.setRequestProperty("User-Agent", USER_AGENT);
        con.setRequestProperty("Accept-Language", "en-US,en;q=0.5");
        con.setRequestProperty("Content-Type", "application/json");

        // Send post request
        con.setDoOutput(true);
        DataOutputStream wr = new DataOutputStream(con.getOutputStream());
        wr.writeBytes(json);
        wr.flush();
        wr.close();

        return getResponse(con.getInputStream());
    }