Re: UDP multicast

[Adrian Sietsma <adrian_groups@...>]

Mike Pall wrote:
> You need a specific order of actions for Windows:
> 1. Create UDP socket
> 2. Set SO_REUSEADDR option
> 3. Bind addr = INADDR_ANY, port = multicast-port
> 4. IP_ADD_MEMBERSHIP multiaddr = multicast-group
Exactly what I'm doing. Within a single app - no problem, I can bind as many
sockets (at least 3) exactly as documented.

The second copy of the app fails on bind().

> See:
>   http://msdn.microsoft.com/en-us/library/ms740621(VS.85).aspx
>   http://support.microsoft.com/default.aspx?scid=kb;en-us;131978
>
> --Mike

Having read that ms stuff yet again, it would appear that the behaviour
depends on
a/ whether the first socket sets so_reuseaddr or not
b/ whether the listener is bound to a wildcard address (which is recommended
for udp multi).

I can try first binding without reuseaddr, then retry with reuseaddr if the
first bind returns "INUSE";
also bind to the local multicast i/f rather than INADDR_ANY.

But not tonight.
Thanks

Adrian