[Interest] Qt polls available Wifi interfaces every 10 seconds for available networks, Windows 7, Qt 5.3.2

[Andre Barth]

[changed subject - was RE: [Interest] Running FancyBrowser / QtWebKit example causes periodical wifi network delay & VOIP interruption, Qt 5.3.2, Windows 7 x64]

Hi all,

I looked into that today again and it looks as if Qt's "Network Configuration Manager" was polling the Wifi engine every 10 seconds for available networks.

This in turn will call Windows' WlanScan function which "... requests a scan for available networks on the indicated interface..."
(see qnativewifiengine::requestUpdate, line 517)

This is causing the interruption of the network traffic on the interface (and the problems with VoIP apps running in parallel)

So, my follow-up questions would be:


1)      What's the reason to have this turned on, i.e. scanning all available networks all the time?


2)      Any ways to disable that and/or workarounds?


3)      Other recommendations?
e.g. would one have to keep the life time of a QNetworkAccessManager instance to the bare minimum?


Thanks,
Andre


From: interest-bounces+andre.barth=autodesk.com at qt-project.org [mailto:interest-bounces+andre.barth=autodesk.com at qt-project.org] On Behalf Of Andre Barth
Sent: Thursday, January 29, 2015 8:47 AM
To: Allan Sandfeld Jensen; interest at qt-project.org
Subject: Re: [Interest] Running FancyBrowser / QtWebKit example causes periodical wifi network delay & VOIP interruption, Qt 5.3.2, Windows 7 x64


Hi Allan,



thanks for the prompt reply.



>>> QtWebKit/fancybrowser doesn't do anything on it own, only when instructed by the user or web-site is any traffic initiated.

Understood - it must/could be the QWebView that the example is using.

But even starting the browser with no URL (i.e. not the default <http://www.qt-project.org>) is showing that issue (presumably wifi only)



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and so on...



>>> Start by logging the network traffic and see what it is

I've done that already but I didn't spot anything obvious. Will have to go back, I guess ;-)



I'm not the network expert, obviously, but could it be that Qt somewhere queries the network stack / driver /adapter or whatever which causes the IO to hang, i.e. no traffic is actually sent / received at all by the Qt app? But that periodic check or query just causes the adapter to delay the network IO? Maybe somewhere in the QNetworkManager(Engine/Service) classes?



Thanks,

Andre



-----Original Message-----
From: Allan Sandfeld Jensen [mailto:carewolf at gmail.com] On Behalf Of Allan Sandfeld Jensen
Sent: Thursday, January 29, 2015 12:43 AM
To: interest at qt-project.org<mailto:interest at qt-project.org>
Cc: Andre Barth
Subject: Re: [Interest] Running FancyBrowser / QtWebKit example causes periodical wifi network delay & VOIP interruption, Qt 5.3.2, Windows 7 x64



On Wednesday 28 January 2015, Andre Barth wrote:

> Hi all,

>

> When running the Fancybrowser example from the Qt 5.3.2 SDK I'm

> experiencing a periodical delay in transmitting network data over my

> wifi connection.

>

> Doing a parallel [ping -t] to another machine inside the same

> subnetwork shows a spike-like increase of the ping time every 5

> seconds or so. We cannot use voip / lync whilst the Qt-application is

> running due to the constant break-up of the data transmission.

>

> Any ideas which area in the Webkit(?) code base might be causing that

> and/or where to best start looking?

>

Start by logging the network traffic and see what it is. Also if you believe it is QtWebKit you should check what website causes it. QtWebKit/fancybrowser doesn't do anything on it own, only when instructed by the user or web-site is any traffic initiated.



Best regards

`Allan
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