private static void toSendRegistrationIdServer(Context context, String key) throws IOException {

        try {
            URL url = new URL(context.getString(R.string.sender_url));

            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setRequestMethod("POST");
            connection.setDoOutput(true);

            OutputStream os = connection.getOutputStream();
            os.write(("acao=registrar&regId=" + key).getBytes());
            os.flush();
            os.close();
            connection.connect();
            int responseCode = connection.getResponseCode();
            if (responseCode != HttpURLConnection.HTTP_OK) {
                throw new RuntimeException("Error saving server");
            }
        }catch (Exception e){
            e.getStackTrace();
        }
    }