Howto activate the LowLatency on TCPClient on Windows

adib taraben

Hello,
I am Using Qt5.13.0/win/MInGW64bit

I try to setup LowLatency TCP Connection

void MyInterface::socketConnected()
{
    qDebug() << "socketConnected";
    QTcpSocket *socket = static_cast<QTcpSocket *>(QObject::sender());
    socket->setSocketOption(QAbstractSocket::LowDelayOption, 1);
}

But I encounter still a 10msec delay. After write I also do flush for the socket.
When I check Socket Option then LowDelayOption is 1.

please advice how to setup LowDelay on TCPClient socket.

Thanks, Adib.

Christian Ehrlicher

@adib-taraben said in Howto activate the LowLatency on TCPClient on Windows:

But I encounter still a 10msec delay.

Are you calling flush() after write()?

adib taraben

@Christian-Ehrlicher

yes, I do

byteswritten = socket->write(data, maxSize);
socket->flush();
qDebug() << "latency: " << socket->socketOption(QAbstractSocket::LowDelayOption);

... and when I check theoption; it is still set to 1.

Adib.

Christian Ehrlicher

Reading the documenation I don't see why the delay should be below 10ms - it only tells the OS to flush as fast as possible. How do you measure. And since this is an OS specific option I don't think Qt can do anything for it (except flushing it's internal buffers so the OS can do it's work which you're doing).

adib taraben

ah I forgot to mention:
there is no difference noticable when there is LowDelayOption not set.

Adib.

aha_1980

@adib-taraben

Thats probably because LowDelayOption is something different than you expect.

So again the question: what do you measure (and how) resp. what is too slow for you.

Regards