Re: [lwip-users] Maximum retransmission value

[address@hidden]

In your situation, the portable way would be to use non-blocking connect 
and then use select to implement a timeout. However, the lwIP socket API 
does not support non-blocking connect, yet (but I think there's a patch 
for that available on savannah).

You can still implement a timeout using the raw API though: even while 
connecting, the poll callback function of the pcb will be called. You 
can implement a timeout there.

Simon


Alain Mouette wrote:
> Hi Simon,
>
> I also need to do the same (it is in my todo list).
>
> The reaso to do so is quite reasonable: I am connecting to a server over 
> GPRS, I have a list of servers and I try all of them sequentialy twice. 
> The probelm is that each SYN is billed and thus excesses have to be avoided.
>
> Lont-time experience in *this situation* shows that if the server does 
> not answer after a few seconds, it is not worth waiting any further. 
> Usualy a second atempt (which will use a different return port) will work.
>
> Thanks,
> Alain
>
> address@hidden escreveu:
>   
> > Changing these defines is generally not a good idea, unless you have 
> > detailed knowledge of what they do in the tcp stack. You might risk 
> > unstable connections on networks which are not 100% safe against packet 
> > loss, and you also might risk interoperability with other network 
> > stacks/devices.
> >
> > In general, it is better to design your communication protocol in a way 
> > to detect a timeout instead of changing the timeout at TCP level, where 
> > you change it for all connections - although you might only need the 
> > timeout for a dedicated control connection (or something like that).
> >
> > Simon
> >
> >
> > PELISSIER Christophe wrote:
> >     
> > > Hi,
> > >  
> > > I want to speed up the connection error detection of my application.
> > > Is decreasing the TCP_MAXRTX and TCP_SYNMAXRTX value a good way to be 
> > > aware rapidely that a connection has been lost.
> > >  
> > > Is there any risk to decrease TCP_MAXRTX from 12 (default value in my 
> > > lwipopts.h) to 6 and TCP_SYNMAXRTX from 6 to 3?
> > >  
> > > What can be the side effect that i must take care of?
> > >  
> > > Thanks for your support.
> > >  
> > > Regards,
> > > Christophe
> > >  
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