[Freeciv-Dev] Re: (PR#6707) Announce server on LAN

["Todd Goodman" <tsg@xxxxxxxxxxxxx>]

* Raimar Falke <i-freeciv-lists@xxxxxxxxxxxxx> [031103 11:30]:
> On Sun, Nov 02, 2003 at 01:51:03PM -0800, andrearo@xxxxxxxxxxxx wrote:
> > As a user you don't have to setup anything. The application layer
> > software in the client and server tells the kernel to give it
> > packets from the multicast group.  I found this useful:
> > http://www.tldp.org/HOWTO/Multicast-HOWTO-2.html
> 
> Looking at this and pinging around on some systems I got responses
> when I ping 224.0.0.1 but no answer when I used 225.0.0.1. This is
> logical from the above URL:
> 
>    224.0.0.1 is the all-hosts group. If you ping that group, all
>    multicast capable hosts on the network should answer, as every
>    multicast capable host must join that group at start-up on all it's
>    multicast capable interfaces.
> 
> This means that none of the other hosts which answered to 224.0.0.1
> are part of 225.0.0.1.

That's because they haven't joined the group by default which would seem
like the desired behavior?

If you had a patched server and client machine then they would have
answered your ping...

> 
> In addition the URL states:
> 
>    In any case, range 224.0.0.0 through 224.0.0.255 is reserved for
>    local purposes (as administrative and maintenance tasks) and
>    datagrams destined to them are never forwarded by multicast
>    routers.
> 
> So if we choose 224.0.0.1 we know that all hosts are on this group AND
> we know that the TTL is irrelevant since the packets are routed.
> 
> The only problem I see is that the server is behind a router. So how
> do you define LAN?
> 
> If all this is correct I'm favoring as the default a scan in 224.0.0.1
> with no special TTL and (optionally if you want to code it) "an export
> mode" where you can input a special multicast group and optionally a
> TTL.

But why would you send all hosts on the local network Freeciv specific
packets?

That seems like a good way to get administrators mad at Freeciv and any
users running it.

It seems like the original patch with both client and server joining
225.0.0.1 would be better and work better.

I do think the TTL should be 1 by default though to keep it on the local
LAN.  With both server and client config for greater TTL then it will
work for as broad a definition of LAN as one would like.

Just my $.02,

Todd

> 
>       Raimar
> 
> -- 
>  email: rf13@xxxxxxxxxxxxxxxxx
>   One nuclear bomb can ruin your whole day.