private void queue(Response res) {
            String tag = res.getTag();
            if (tag != null) {
                ResultListener rl = listeners.get(tag);
                if (rl != null) {
                    if (res instanceof Result) {
                        rl.receive((Result) res);
                    } else {
                        //          rl.error((Error)res);
                    }
                }
            }
        }