While reading the ArsTechnica review of MAC OS 10.6 I came across this neat feature. You can wake a sleeping Mac (to gain SSH access for example) as long as the “Wake for Ethernet network administrator access” option is checked in the Engery saver settings. The newest Airport Extreme and Time Capsule hardware is capable of waking a 10.6 Mac that your trying to connect to remotely.
[ I don’t like to leave my Mac Pro turned on 24 hours a day, especially during the summer in my un-air-conditioned house. But I do want to have access to the files on my Mac when I’m elsewhere—at work, on the road, etc. It is possible to wake a sleeping Mac remotely, but doing so requires being on the same local network.
My solution has been to leave a smaller, more power-efficient laptop on at all times on the same network as my Mac Pro. To wake my Mac Pro remotely, I ssh into the laptop, then send the magic “wake up” packet to my Mac Pro. (For this to work, the “Wake for Ethernet network administrator access” checkbox must be checked in the “Energy Saver” preference pane in System Preferences.)
Snow Leopard provides a way to do this without leaving any of my computers running all day. When a Mac running Snow Leopard is put to sleep, it attempts to hand off ownership of its IP address to its router. (This only works with an AirPort Extreme base station from 2007 or later, or a Time Capsule from 2008 or later with the latest (7.4.2) firmware installed.) The router then listens for any attempt to connect to the IP address. When one occurs, it wakes up the original owner, hands back the IP address, and forwards traffic appropriately.
You can even wake some recent-model Macs over WiFi. Combined with MobileMe’s “Back to My Mac” dynamic DNS thingamabob, it means I can leave all my Macs asleep and still have access to their contents anytime, anywhere. ]