protected function handleHeartbeatAck($data)
    {
        $received = microtime(true);
        $diff     = $received - $this->heartbeatTime;
        $time     = $diff * 1000;

        $this->heartbeatAckTimer->cancel();
        $this->emit('heartbeat-ack', [$time, $this]);
        $this->logger->debug('received heartbeat ack', ['response_time' => $time]);
    }