test

    }

    ssize_t sent = udp::sendBatch(datagrams, dest, dest_len);

    _send_batch.clear();

    if (sent > 0) {

        _last_activity = std::chrono::steady_clock::now();

        const size_t sent_count = static_cast<size_t>(sent);

        if (sent_count >= _send_batch.size()) {

            _send_batch.clear();

        } else {

            _send_batch.erase(_send_batch.begin(), _send_batch.begin() + sent_count);

        }

        return sent;

    }

    if (sent == 0) {

        return 0;

    }

    // Keep unsent packets queued so the caller can retry after writable/ACK progress.

    return sent;

}