RE : [lwip-users] netconn_recv blocking forever

[Frédéric BERNON]

Hi Mateusz,

I just terminate new patch about netconn_recv to implement SO_RCVTIMO (previous 
give problems to others developers), but, it will only work on UDP in a first 
time (and, I suppose you use TCP). About KeepAlives, I have to change Keepalive 
feature to enable to change value per socket, but in a first time, it's not - 
yet - possible.

Wait and see... 
  
====================================
Frédéric BERNON 
HYMATOM SA 
Chef de projet informatique 
Microsoft Certified Professional 
Tél. : +33 (0)4-67-87-61-10 
Fax. : +33 (0)4-67-70-85-44 
Email : address@hidden 
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P Avant d'imprimer, penser à l'environnement
 


-----Message d'origine-----
De : address@hidden [mailto:address@hidden De la part de Mateusz Plocinski
Envoyé : jeudi 8 mars 2007 15:14
À : Mailing list for lwIP users
Objet : Re: [lwip-users] netconn_recv blocking forever


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
>
>
>
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> lwip-users mailing list
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> http://lists.nongnu.org/mailman/listinfo/lwip-users
>


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