Share your computer’s resources when it’s in sleep
If you’re sharing your computer’s resources, such as a shared printer or iTunes playlist, you can set your computer to wake from sleep when other users access those resources.
To use this feature, you need an Apple wireless device that supports 802.11n and that has the latest firmware installed. Also, if you’re using a portable Mac, it needs to be charging using a power adapter.
Choose Apple menu > System Preferences, then click Energy Saver.
Select any of the available “Wake for…” options, for example, “Wake for Ethernet Network Access.” (Different options are available, depending on how you’re connected.)
When the “Wake for network access” checkbox is selected, your Mac wakes at the following times:
When a user at another computer accesses your computer’s shared resources.
At regular intervals so that your Mac can notify other computers on the network that its resources are available.