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Date: Fri, 12 Apr 2013 17:56:06 +0200
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: UDP/DTLS sockets communication pattern is broken in Cygwin
Message-ID: <20130412155606.GF11358@calimero.vinschen.de>
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References: <031222CBCF33214AB2EB4ABA279428A30140C1ACA374 AT SJCPMAILBOX01 DOT citrite DOT net> <20130411212115 DOT GA1376 AT ednor DOT casa DOT cgf DOT cx> <031222CBCF33214AB2EB4ABA279428A30140C1ACA378 AT SJCPMAILBOX01 DOT citrite DOT net> <20130412114354 DOT GC11358 AT calimero DOT vinschen DOT de> <031222CBCF33214AB2EB4ABA279428A30140C1ACA37B AT SJCPMAILBOX01 DOT citrite DOT net>
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User-Agent: Mutt/1.5.21 (2010-09-15)

On Apr 12 08:44, Oleg Moskalenko wrote:
> 
> > 
> > However, I think I found a workaround on the application level.
> > Apparently all packets sent to a specific address are sent to the first socket
> > which has been bound to the address.  If that socket has been closed, the next in
> > line gets the packets (unless it has been connected and the sender is not the
> > connected address).  So what I did was this:
> > 
> > Before starting step 14, I created a third socket, which then replaced the server
> > socket:
> 
> Thank you, Corinna, for the reply and for the idea.
> 
> Unfortunately, the workaround will work well only in the case of a single client. 
> In the multiple clients scenario, it will create a sort of race condition: 
> 
> 1) some packets already scheduled by OS to the "original" packet will be lost;
> 2) some packets delivered in between the sockets destruction/creation will be wrongly rejected.
> 
> But this is better than nothing. I'll think whether we can live with it.

Too bad.  I don't know the DTLS protocol, but isn't it possible to do
the server part with a single UDP socket?  If you keep track of the
already connected clients, you know if the just incoming packet is a
connected or connecting client, and then you can use different threads
to handle the packet further.


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

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