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Date:	Fri, 20 Feb 2009 13:55:34 +0100
From:	Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To:	cygwin AT cygwin DOT com
Subject:	Re: Problem Adding Membership Multicast Errno 22
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On Feb 20 13:48, Corinna Vinschen wrote:
> On Feb 20 04:05, victhor_1983 wrote:
> > 	status= setsockopt(Descriptor, IPPROTO_IP, IP_ADD_MEMBERSHIP, &Multic,
> > sizeof(Multic));
> >         if (status<0){
> >            printf("Fallo al añadir el grupo de Multicast, codigo %i\n",
> > errno);
> > 	}
> 
> I'm sorry, I can't tell you why this doesn't work.  Cygwin's setsockopt
> function is basically just a shim between application and Winsock's
> setsockopt call.  It only performs special actions on a very limited
> set of options, only two actually: (SOL_SOCKET, SO_REUSEADDR) and
> (IPPROTO_IP, IP_TOS).  I'm also quite multicast illiterate.  Is it
> possible that you have to use the IP_MULTICAST_IF option on Windows
> before you can use IP_ADD_MEMBERSHIP?!?

Here's one idea:  Is it possible that your application includes
winsock.h?  If so, don't do that, use the POSIX headers for socket and
ip stuff.  Winsock.h is the WInsock specific header file for
applications using the old Winsock 1.x API.  In that API,
IP_ADD_MEMBERSHIP is defined as the value 5.

However, the newer Winsock 2.x API, which is used by Cygwin under the
hood as well, defines IP_ADD_MEMBERSHIP as the value 12.  So, if there's
any chance that you're including the winsock.h header, remove it and
only use Cygwin's header files, not the Winsock specifc header files.


Hope that helps,
Corinna

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

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