I'm looking for an X11 server on the iPhone to be able to use the NX protocol. There are RDP clients, Citrix clients, VNC clients, but no X11 server...
Do you think it is possible to port (or create ?) an X11 server (by example kdrive modified for Cocoa) for the iPhone? Does it have enough CPU-power or memory for that? How would you do that? Are there alternatives?
First you should take a look at Zingersoft. Your second step will probably be working to get XQuartz compiling for iPhone.
It certainly has enough CPU power and memory - X11 has been running on < 10mhz machines since it's inception. Of course, these didn't support blending, anti-aliasing, shape extensions, etc. Clocking in at 600mhz+ and a modern graphics chip, the iPhone is a smoking monster machine.
Zingersoft though provides, as Rob Napier said, an X server, so obviously must be possible :)
Yes, it's possible. Whether it makes sense or not is a different matter - X is not only the drawing protocol, it's the interaction model as well. You'd be hard-pushed to do right-clicks, control-characters or most other operations that X programs will want to do.
Frankly, you're probably better off hosting a VNC session onto a remote X session held by a run of the mill Linux box rather than going down this road if all you want to get is bits on the screen.