[Interest] QNetworkAccessManager and HTTP persistent connection

Thu Nov 28 08:27:52 CET 2013

Maybe you need to delete the first reply, and possibly processEvents before
you make the second request? 

Hope that helps, 

Tony

From: interest-bounces+tony=rightsoft.com.au at qt-project.org
[mailto:interest-bounces+tony=rightsoft.com.au at qt-project.org] On Behalf Of
iMath
Sent: Thursday, 28 November 2013 5:56 PM
To: Mandeep Sandhu
Cc: interest
Subject: Re: [Interest] QNetworkAccessManager and HTTP persistent connection

Thank you for your prompt! 

I think I should give my question a clear description.

The "Connection:keep-alive"  is in the  reply header, when I call close() of
the reply, the connection is still on ,I wonder how can I send a second
request to the server using this connection in such  case ?

If I just simply make a second request like the following 

1.  manager->get( <http://qt-project.org/doc/QNetworkRequest.html>
QNetworkRequest( <http://qt-project.org/doc/QUrl.html> QUrl("url")));

it seems a another new TCP connection to the server will be initiated (I
have checked with a network sniffer)

------------------ Original ------------------

From:  "Mandeep Sandhu";<mandeepsandhu.chd at gmail.com>;

Date:  Wed, Nov 27, 2013 04:57 PM

To:  "iMath"<2281570025 at qq.com>; 

Cc:  "Interest at qt-project.org"<interest at qt-project.org>; 

Subject:  Re: [Interest] QNetworkAccessManager and HTTP persistent
connection

Please reply to the whole list and not to me individually. Maybe
someone on this list might have a more specific answer.

Both pipelined and persistent connections use a single TCP connection.

But in pipelining, the client can send multiple requests WITHOUT
WAITING for a response from the server whereas in persistent
connections the second (or subsequent) responses are sent only after
receiving response of the previous request:
http://en.wikipedia.org/wiki/HTTP_pipelining

If the server has not sent a "Connection: Close" then closing the
connection from the client _might_ to be a bug.

How are you ascertaining that the client is initiating the close? Does
the packet sniffer show the client sending a FIN packet?

-mandeep

On Wed, Nov 27, 2013 at 12:21 PM, iMath <2281570025 at qq.com> wrote:
> HTTP persistent connection, also called HTTP keep-alive, or HTTP
connection
> reuse, is the idea of using a single TCP connection to send and receive
> multiple HTTP requests/responses, as opposed to opening a new connection
for
> every single request/response
> pair.(http://en.wikipedia.org/wiki/HTTP_persistent_connection)
>
> "Connection:keep-alive"  is in the  response header.
>
>  I want to send my a second http request using the same connection that
was
> setup when the first HTTP request was made. how can this be achieved
through
> Qt?
>
>
> ------------------ Original ------------------
> From:  "Mandeep Sandhu";<mandeepsandhu.chd at gmail.com>;
> Date:  Tue, Nov 26, 2013 08:50 PM
> To:  "iMath"<2281570025 at qq.com>;
> Cc:  "Interest at qt-project.org"<interest at qt-project.org>;
> Subject:  Re: [Interest] QNetworkAccessManager and HTTP persistent
> connection
>
> I think I was wrong in telling you that HTTP persistent connection was
> same as HTTP pipelining. They aren't.
>
> In HTTP pipelining multiple HTTP requests can be made w/o waiting for
> response of each connection. Whereas in HTTP persistent connection
> (default as you said in HTTP 1.1), the same TCP connection is used for
> sending HTTP request "one-after-another".
>
> Can you check if the the outgoing HTTP request has the "Connection:
> keep-alive" set in its (HTTP) header. Also, I've read that sometimes
> webservers will send a "Connection: Close" header in its response in
> which case the client will close it's connection, so check if the
> webserver is playing nice with your request. Which webserver are you
> testing against?
>
> HTH,
> -mandeep
>
>
>
> On Tue, Nov 26, 2013 at 5:19 PM, iMath <2281570025 at qq.com> wrote:
>> unfortunately ,it doesn't work on Qt4/WinXP
>> I have set
>> request.setAttribute(QNetworkRequest::HttpPipeliningAllowedAttribute,
>> true);
>>
>> but the attribute QNetworkRequest::HttpPipeliningWasUsedAttribute in the
>> reply is false .
>> ------------------ Original ------------------
>> From:  "Mandeep Sandhu";<mandeepsandhu.chd at gmail.com>;
>> Date:  Tue, Nov 26, 2013 02:14 PM
>> To:  "iMath"<2281570025 at qq.com>;
>> Cc:  "interest"<interest at qt-project.org>;
>> Subject:  Re: [Interest] QNetworkAccessManager and HTTP persistent
>> connection
>>
>> On Sat, Nov 23, 2013 at 7:15 PM, iMath <2281570025 at qq.com> wrote:
>>> HTTP 1.1 supports persistent connection by default, so I want to send my
>>> a
>>> second http request using the same connection that was setup when the
>>> first
>>> HTTP request was made. how can this be achieved through Qt?
>>
>> I think you meant HTTP "pipelining" (that's the jargon used inside Qt
>> code). I'm not 100% sure but in Qt5, the default _should_ be to use
>> HTTP pipelining.
>>
>> In any case, you can explcitly check in the reply object if pipelining
>> was indeed used or not. Check for the
>> "QNetworkRequest::HttpPipeliningWasUsedAttribute" attribute in your
>> reply.
>>
>> Alternately, you can try and explicitly request this behaviour by
>> setting the n/w request attribute:
>>
>> request.setAttribute(QNetworkRequest::HttpPipeliningAllowedAttribute,
>> true);
>>
>> If it still doesn't work, then it might be a bug. What platform are
>> you running your on, BTW?
>>
>> HTH,
>> -mandeep
>>
>>
>>
>>>
>>> If I simply make the second request after the first one finished like
the
>>> following
>>>
>>> QNetworkAccessManager *manager = new QNetworkAccessManager(this);
>>> connect(manager, SIGNAL(finished(QNetworkReply*)),
>>>         this, SLOT(replyFinished(QNetworkReply*)));
>>>
>>> manager->get(QNetworkRequest(QUrl("http://qt-project.org")));
>>>
>>> it seems a new TCP connection to the server will be initiated (I have
>>> checked with a network sniffer) The experiment also says: If the reply
is
>>> deleteLater() or abort() within finished() signal, the connection will
be
>>> closed.
>>>
>>>
>>> _______________________________________________
>>> Interest mailing list
>>> Interest at qt-project.org
>>> http://lists.qt-project.org/mailman/listinfo/interest
>>>

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