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

["andrearo@xxxxxxxxxxxx" <andrearo@xxxxxxxxxxxx>]

On Sun, 2 Nov 2003, Raimar Falke wrote:
> On Sun, Nov 02, 2003 at 10:48:29AM -0800, andrearo@xxxxxxxxxxxx wrote:
> > On Sun, 2 Nov 2003, Raimar Falke wrote:
> > > On Fri, Oct 31, 2003 at 01:04:05PM -0800, andrearo@xxxxxxxxxxxx wrote:
> > > >
> > > > Hi everyone,
> > > > One of the features I miss in Freeciv is to get a list of servers on the
> > > > LAN that the client can connect to, when setting up local games. So I 
> > > > just
> > > > had to implement it :)
> > > >
> > > > It works as follows: The client multicasts an UDP packet to the LAN, 
> > > > with
> > > > TTL=4 so that the packet doesn't leave the LAN. The server then get's 
> > > > the
> > > > packet, and send a response with it's info. The list of LAN servers in 
> > > > the
> > > > connect dialog is updated, just like the list of Metaservers.
> > >
> > > Nice idea. I have a problem however with the constants. Why TTL=4? Why
> > > not 3 or 5?
> >
> > Good question.. It depends about how far you want the packet to reach,
> > since TTL is decremented every time a packet goes through a router.
>
> > It could probably also be 3 or 5, depending about how you define
> > "LAN".
>
> And that is the point. If we hardcode it in the code we have to choose
> a good value. A not hardcoded solution would be better. Is this
> possible?

Do you want TTL as a runtime parameter to the client and server? I've
never used any software that requires you to do that.
I can't think of another way to set the TTL.

> > > Why a SERVER_LAN_GROUP of 225.0.0.1? Can't this be
> > > autodetected somehow?
> >
> > The server and client have to be in the same multicast group.
>
> Uhh I overlooked this. I assumed that the patch uses a broadcast. So
> what requirements are needed to use multicast? What setup must be done
> to enable it? Where do I have to set 225.0.0.1 to join this multicast
> group?

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

 Andreas Røsdal