Re: [lwip-users] netconn_recv blocking forever

[Mateusz Plocinski]

Hi, thanks for fast answer.
Of course I could do as you said but my problem is that thread is
blocked in netconn_recv so I cant do anything while waiting for data.
I dont want to use raw api or to go deeper into the stack (it would
take me too much time... and my whole application is written using
netconn socket api).
Is it possible to change netconn_recv to wait for data for some time
and then return after timeout? It would solve my problem. I'm trying
to work this problem around for some time but I'm affraid to change
anything in the core of lwip (too many things which are difficult to
understand, too few time for that...).

Mateusz Plocinski

2007/3/8, Kieran Mansley <address@hidden>:
> On Thu, 2007-03-08 at 14:27 +0100, Mateusz Plocinski wrote:
> > Hi,
> > I'm using an ARM7 FreeRTOS port of lwip. I'm trying to implement a
> > thread which waits for data from PC using netconn_recv. Everything
> > works fine in most situations (for week or longer without any
> > problems), but when I disconnect network cable or PC simply hangs up
> > without closing a connection, my lwip socket thread still sits in
> > netconn_recv function.
> >
> > Is there any way to check if connection isnt dead while thread is
> > blocked in netconn_recv? I need to know in few seconds if I should
> > close connection because I need to quickly restart connection to my
> > ARM hardware (and I have only on thread so I cant open more sockets to
> > wait for connection).
>
> I think the short answer to this is "No".  There are all sorts of
> network faults (e.g. unplugged cables, or server dieing without closing
> connections, etc) that aren't detectable by one end of the connection.
>
> You could try using the TCP KEEPALIVE support, but that takes a minimum
> of two hours to report a connection as broken, rather than a few
> seconds, because TCP is designed to survive short outages of a few
> seconds.
>
> You could modify your application and server so that they (for example
> once every 10 seconds) send each other a "are you still there" message,
> and reply "yes I'm still here".  Then, if you don't receive the reply
> you can guess that something has gone wrong.
>
> Kieran
>
>
>
> _______________________________________________
> lwip-users mailing list
> address@hidden
> http://lists.nongnu.org/mailman/listinfo/lwip-users