Roger's odd programming question of the week

[Roger Oberholtzer]

On Fri, 2005-09-02 at 15:12, Rick Sivernell wrote:
> Roger
> 
> 
>   As per my source, Unix Network Programming", the following excerpts:
> 
> On IPv4 & IPv6 work similarly, The app on host, receiving host, starts & creates a
> UDP socket and binds to port 123, and joins the multicast group. MC on a single lan
> is simple, 1 host sends a MC packet & any interested host receives it, the benifit of
> MC over broadcast is reduced load on all interested hosts.
> 
> there are many more pageson this. does this help?

This I know. But it doesn't really answer the question: will a listener
on a local broadcast address see multicast packets?

Mulitcast addresses are in the range 224.0.0.1 thru 239.255.255.255. So,
if I am listening for broadcasts on 255.255.255.255 (on a local network
segment!), would I see something for MC group 244.1.1.1? You might sat
so as the masks allow it. But the multicast bits seem to be special.

BTW, to see what multicast hosts are on your net, do:

	ping 224.0.0.1

os to check a specific card:

	ping -I eth1 224.0.0.1

Or try

	ping 224.0.0.2

to see if there are any MC routers on your net. 


> 
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