Machine sleeping is a bit of a mystery to many of us. It's one of those magical things that when it works right, really makes using a laptop computer, or Media Center recording machine a thing of beauty. I've been meaning to write an article on Magic Packets, but I see Robert Hensing just posted an article called, "Hybrid sleep in Vista and S0 - S5 explained". Robert has some links to good resources on the subject so check it out.
I started investigating sleep states due to an issue that cropped up on my Windows Vista Ultimate desktop machine here at my house. You see, my Vista box wouldn't stay asleep. It would sleep when it was supposed to (15 minutes), but 60 seconds later it would wake right back up. That's annoying. How's a machine going to get any rest?
Since I had not seen this condition before, I started looking at new additions to the machine and network. I wanted to point the finger at my HDHomeRun network tuner. Maybe the new video card or router? Nope. As it turns out, it was probably my busy network keeping it awake. I know how it feels.
The fix was simple. I just needed to set the network card so that it would only wake the machine when it received a "Magic Packet". Now why would I do that? Or more important, what device will send one of those magical frames? Well, as it turns out, our friend the Xbox 360 does. So after making the appropriate change to the nic properties, the machine wakes up for three reasons. If I hit the power button, if it's time to record a TV show, and if I tell my Xbox 360 to use the Media Center extender feature. When Xbox does that, it sends the magic packet, wakes the machine, logs in, and starts the remoting experience. Pretty kewl eh? Magic.