Problem Adding Membership Multicast Errno 22

Brian Ford Brian.Ford@FlightSafety.com
Fri Feb 20 15:40:00 GMT 2009


On Fri, 20 Feb 2009, victhor_1983 wrote:

> Thanks for the advice, I just tried it, but I keep getting the same mistake.
> Maybe there is no IP_ADD_MEMBERSHIP option for Multicast in Cygwin?

There definately is as I use it daily.  I'm not sure the cause of the
EINVAL, but without a bind, it definately won't work on Windows:

http://www.cygwin.com/ml/cygwin/2006-08/msg00703.html

I assume you aren't trying to define IP_ADD_MEMBERSHIP yourself?

http://cygwin.com/ml/cygwin/2005-09/msg01007.html

Are you sure the interface IP exists and is up with a link on your
test system?

> >> 	Multic.imr_interface.s_addr=inet_addr("138.4.32.34");

> Corinna Vinschen-2 wrote:
>
> > Is it possible that you have to use the IP_MULTICAST_IF option on
> > Windows before you can use IP_ADD_MEMBERSHIP?!?

Nope.  IP_MULTICAST_IF specifies which interface to use for outbound
traffic.  IP_ADD_MEMBERSHIP tells a particular interface to receive
multicast traffic.  That IP must be present and up with link, or EINVAL
will be returned.

-- 
Brian Ford
Staff Realtime Software Engineer
VITAL - Visual Simulation Systems
FlightSafety International
the best safety device in any aircraft is a well-trained crew...

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