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Date: Fri, 20 Feb 2009 13:48:14 +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 04:05, victhor_1983 wrote:
> 
> Hi,
> 
> I have written a C++ program for a Multicast Client that compiles and runs
> on Ubuntu. I tried to compile and run it on Cygwin version 1.5.25 (June
> 2008). However, when I run the code, the Multicast receiving socket doesn't
> seem to work. The problem comes when I use setsockopt() to add Multicast
> membership. The errno() declaration returns 22 (EINVAL), but I cannot find a
> solution. My code is:
> 
> 	int Descriptor, Descriptor2, payloadoffset,sqnum, T_ns, status;
> 	long nsegundos,Dnsegundos, segundos,  Dsegundos;
> 	struct sockaddr_in Direccion, Direccion2;
> 	unsigned short Puerto;
> 	struct timespec valorcontador,valorcontador2,Next;
> 	struct ip_mreq Multic;
> 
>         Descriptor=socket(AF_INET,SOCK_DGRAM,0);
> 	Puerto=12100;
> 	Direccion.sin_family=AF_INET;
> 	Direccion.sin_port=htons(Puerto);
> 	Direccion.sin_addr.s_addr=inet_addr("224.0.22.1");
> 	memset(&(Direccion.sin_zero),'\0',8);   
> 
>        	Multic.imr_multiaddr.s_addr=inet_addr("224.0.22.1");
> 	Multic.imr_interface.s_addr=inet_addr("138.4.32.34");
> 	status= setsockopt(Descriptor, IPPROTO_IP, IP_ADD_MEMBERSHIP, &Multic,
> sizeof(Multic));
>         if (status<0){
>            printf("Fallo al aņadir 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?!?


Corinna

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

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