Relationship between X and clients.
 

Is there a max number of clients X can serve (locally)? Also, would a desktop like kde / gnome, also be considered a client to the X server? I'm just trying to get the big picture.

I've come across "maximux nubmer of connections reached" problems on the web, but these seem to be across a network. So I don't know if these are max clinets of the network, the X server, or both.

I know of no limits to the number of X clients you can have running at once. I'd presume it'd be limited only by available memory; computer labs with terminals can have 40 or 50 X clients at a time, and probably many more than that in some cases.

I'm a little hazy on what exactly constitutes a client to the X server, though. I think Gnome or KDE would be considered as such, though, since they are making requests to the X server for displaying things. The XFree86 Howto has a little section on how X clients are run, and it looks like any program doing display on the X server would be considered an X client.

edit: Ah, I see what you're asking... whether there's a limit on the number of clients that an X server can serve. The answer is... probably not :)