[Qt-interest] QTcpServer timeout ?

[David Boosalis]

BRM, Atlant.

Thanks for your insight and feedback.  I read up on KeepAlive switch and it
basically does the polling for you without notifying your application as it
is doing so.  I think QTcpServer out to have methods for doing this.  But I
was able to do it with the following lines.


 int sockID = myQtSocket->socketDescriptor();
  flag = 1;
  ret = setsockopt( sockID, SOL_SOCKET, SO_KEEPALIVE, (char *)&flag,
sizeof(flag));


One final question regarding KeepAlive. Should it be done on the server side
or client side, or does it not matter ?



On Tue, Jul 20, 2010 at 2:23 PM, BRM <bm_witness at yahoo.com> wrote:

> There is also another solution, though you may have to fall-back to some
> platform specific code to enable it.
>
> Both Windows and Linux do have system level timers on the sockets. However,
> you can set a KEEP_ALIVE socket option.
> While this can be specified on the socket creation (e.g. open()), it can
> also be set via the socket options (setsockopt() for Linux).
> The KEEP_ALIVE option basically makes the operating system send the
> messages at the TCP protocol layer (per RFC 1122);
> thus you don't have to generate or parse more messages or have to maintain
> a timer yourself to send them.
>
> http://en.wikipedia.org/wiki/Keepalive#TCP_Keepalive
> http://tldp.org/HOWTO/TCP-Keepalive-HOWTO/usingkeepalive.html
> http://msdn.microsoft.com/en-us/library/ms819735.aspx
>
> I could not quickly spot a way to get Qt to do this for you.
>
> HTH,
>
> Ben
>
>
> *From:* Atlant Schmidt <aschmidt at dekaresearch.com>
> *To:* David Boosalis <david.boosalis at gmail.com>; QtInterest <
> qt-interest at trolltech.com>
> *Sent:* Tue, July 20, 2010 4:01:13 PM
> *Subject:* Re: [Qt-interest] QTcpServer timeout ?
>
>  David:
>
>
>
>   It’s quite common for TCP connections of all sorts to have an inactivity
> timer.
>   This is especially true if your session connects through a firewall or a
> “public”
>   medium.
>
>
>
>   Because you often can’t affect the settings of the various inactivity
> timers
>   you may encounter along the way, the usual solution is, as you surmised,
>   the use of keep-alive messages. I’m thinking that every five minutes is
>   too long, but that will depend on your particular circumstances.
>
>
>
>                                     Atlant
>
>
>  ------------------------------
>
> *From:* qt-interest -bounces at trolltech.com [mailto: qt-interest -
> bounces at trolltech.com] *On Behalf Of *David Boosalis
> *Sent:* Tuesday, July 20, 2010 3:51 PM
> *To:* QtInterest
> *Subject:* [Qt-interest] QTcpServer timeout ?
>
>
>
> I have Qt Client applications establishing  connections to server apps
> based using QtTcpServer(s).  The sockets that send data quite often have no
> problem staying connected all day.  However the sockets that send notices
> maybe one every two hours or perhaps just once a day tend to die. I never
> see a disconnect, but the socket just seems to go to sleep as data fails to
> arrive to the server.  I was wondering if a time out occurring due to  the
> lack of activity going across the socket.  I looked at the QTcpServer class
> for a method that might turn off such a timer but did not see any.  Perhaps
> this behaviour goes beneath QT and into the  Linux Tcp Server design. If so
> is there a low level call I can make on the socket ID to keep the connection
> always alive.  I am thinking about sending a ping every 5 minutes on these
> sockets.
>
> Any advise on how best to fix this time out is very much appreciated.
>
> -David
>
>
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