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

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

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". TTL
is typically over 100 for global packets.

> 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.
As long as it's a class D IP address, it should be ok. right?

>Also this
>   +  for (i = 0; i < 130; i++) {
> 130 looks like it wants a comment.

I sent a patch named lanannouncev2.diff earlier today, where this has been
removed.

>
> The same is true for this 1:
> +  dio_output_init(&dout, buffer, sizeof(buffer));
> +  dio_put_uint8(&dout, 1);

Yes, there should be a comment there.
(It's for versioning.)

> You know that in
> +  unsigned char buffer[MAX_LEN_PACKET];
> ...
> +  if (sendto(sock, buffer, sizeof(buffer), 0, (struct sockaddr *) &addr,
> +      sizeof(addr)) < 0) {
>
> you send 4096 bytes in which you only have 1 byte real payload?!

You're right. There's no need to send any more info to the server,
so just decrease the size of the buffer then.

Please have a look at the updated patch.

 Andreas Røsdal