So, here are some technical details about two computers I'm trying to have interact with each other:

PC: an e-Machines (yeah, I know!) tower with a 2.8ghz processor (single-core), 2 GB RAM, running 32-bit Ubuntu 12.04LTS.

Mac: May 2011 21-inch iMac, 2.5ghz quad-core processor, 16GB RAM, running OSX 10.7.4.

Thing is, it's really cluttering up my space having two monitors, and I figured probably the best way to handle this is to remotely connect to the Ubuntu box from the iMac to do my Ubuntu stuff.

I'm able to do this through my wifi, but the thing is, doing it this way is unbearably slow. So I figured, why not just connect the PC to the Mac using the ethernet ports?

I tried that...but as a result, Ubuntu could actually communicate with the iMac, but not the other way around.

What all should I be looking out for?