Remote Display over Ethernet

Sorry for the odd post, but I'm having trouble finding a solution to my problem.
Sorry also this is for Windows at the moment.
I found a solution with my iPad.

Here it is:
Using DisplayLink, I can use my iPad as another monitor on my PC (Windows 7). Very cool! The PC connect to the iPad over wifi. So I have a roving display.
PC1 ---- wifi ---- iPad( as a monitor)

What I need is:
PC1 ---- wifi (or ethernet) ---- PC2(running software to act as a monitor)

What solutions are out there?
I think there should be a software only solution.
X11 is a possible option.
I want PC2 to act only as another monitor. So PC1 controls what is displayed on it.

I know this is a Mac centric site, and I likely get flamed, but there many sharp people that I hope can help or point me in a direction.

Thanks

 

Yes, I tried Google. But I didn't know what search terms to use.

But Thank you very much for the link. Thats what I'm looking for.