[Interest] Does QNetworkAccessManager support HTTP persistent connections? (keep-alive)

[Marian Beermann]

Correct. If you augment your debugging a little, it is easy to see the
server sending a "Connection: close" header:

qDebug() << ... << reply->rawHeader("Connection");

On 25.07.2018 16:38, Sze Howe Koh wrote:
> Hi all,
> 
> Revisiting this topic after a hiatus. Thanks for confirming, Thiago and Hamish.
> 
> On 13 April 2018 at 10:08, Thiago Macieira <thiago.macieira at intel.com> wrote:
>> On quinta-feira, 12 de abril de 2018 15:44:54 PDT Sze Howe Koh wrote:
>>> Can QNAM re-use a TCP connection for multiple HTTP requests?
>>
>> Yes. It's the default. You don't have to do anything to enable it.
> 
> In a quick test, I used 1 QNAM to download 12 files simultaneously.
> (Windows 10 Pro x64 build 1803, using Qt 5.11.1 + MSVC 2015 32-bit)
> 
> In Wireshark, I expected to see my PC send 6 SYNs (because QNAM does 6
> connections in parallel and re-uses connections) and 12 GETs (because
> I'm downloading 12 files).
> 
> However, I saw my PC send 12 SYNs and 12 GETs. I also saw the server
> send 12 RSTs, 1 after each file finished downloading. My
> interpretation is that the server terminates the connection after each
> GET, which prevents connection re-use. Is this expected?
> 
> Test code:
> 
>     const QStringList urls
>     {
>         "http://download.qt.io/online/qtsdkrepository/windows_x86/desktop/qt5_59/qt.59.win64_msvc2017_64/5.9.0-0-201705291821meta.7z",
>         "http://download.qt.io/online/qtsdkrepository/windows_x86/desktop/qt5_59/qt.59.win64_msvc2015_64/5.9.0-0-201705291821meta.7z",
>         "http://download.qt.io/online/qtsdkrepository/windows_x86/desktop/qt5_59/qt.59.win64_msvc2013_64/5.9.0-0-201705291821meta.7z",
>         "http://download.qt.io/online/qtsdkrepository/windows_x86/desktop/qt5_59/qt.59.win32_msvc2015/5.9.0-0-201705291821meta.7z",
>         "http://download.qt.io/online/qtsdkrepository/windows_x86/desktop/qt5_59/qt.59.win32_mingw53/5.9.0-0-201705291821meta.7z",
>         "http://download.qt.io/online/qtsdkrepository/windows_x86/desktop/qt5_59/qt.59.qtwebengine/5.9.0-0-201705291821meta.7z",
>         "http://download.qt.io/online/qtsdkrepository/windows_x86/desktop/qt5_59/qt.59.qtwebengine.win64_msvc2017_64/5.9.0-0-201705291821meta.7z",
>         "http://download.qt.io/online/qtsdkrepository/windows_x86/desktop/qt5_59/qt.59.qtwebengine.win64_msvc2015_64/5.9.0-0-201705291821meta.7z",
>         "http://download.qt.io/online/qtsdkrepository/windows_x86/desktop/qt5_59/qt.59.qtwebengine.win32_msvc2015/5.9.0-0-201705291821meta.7z",
>         "http://download.qt.io/online/qtsdkrepository/windows_x86/desktop/qt5_59/qt.59.qtvirtualkeyboard/5.9.0-0-201705291821meta.7z",
>         "http://download.qt.io/online/qtsdkrepository/windows_x86/desktop/qt5_59/qt.59.qtvirtualkeyboard.win64_msvc2017_64/5.9.0-0-201705291821meta.7z",
>         "http://download.qt.io/online/qtsdkrepository/windows_x86/desktop/qt5_59/qt.59.qtvirtualkeyboard.win64_msvc2015_64/5.9.0-0-201705291821meta.7z"
>     };
>     QNetworkAccessManager nam;
>     for (auto url : urls)
>     {
>         auto reply = nam.get(  QNetworkRequest( QUrl(url) )  );
>         QObject::connect(reply, &QNetworkReply::finished, [=]
>         {
>             qDebug() << reply->request().url() << reply->readAll().size();
>             reply->deleteLater();
>         });
>     }
> 
> 
> Regards,
> Sze-Howe
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