i'm not sure of the definative answer to this, but it may depend on the motherboard you have, you'll probably need to be using a network card built into the motherboard for starters.
I once had a computer that would wake up just by pinging it, so i think it may be possible to do what you ask
Processor: AMD Athlon(tm) 64 X2 Dual Core Processor 5200+
OpenGL Renderer: nVidia GeForce 9500 GT/PCI/SSE2
Operating System: Fedora release 18 (Spherical Cow)
Desktop Environment: KDE 4.10