Apple just received a patent for a solution to a problem you might have encountered: you need to print to a printer with a power-saving mode—but the printer is in that power-saving mode.

…In many cases, the user must manually walk over to the device and press a button to wake it up, or they simply may not be able to use the device at all. Moreover, a user may not even know of the existence or availability of a device if it is in power-saving mode. When devices are in power-saving mode, they do not broadcast their services on the network, and therefore may not show up in a list of available services. This is especially true if the device has been in power-saving mode for an extended period of time.

Hence, what is needed is a method and an apparatus for allowing the device to enter into a power-saving mode while still maintaining visibility and availability on the network…

— Description, U.S. Patent 7,330,986, February 12, 2008

Apple’s solution is a sleep proxy, a network service that knows how to wake power-saving devices when necessary, and knows how to keep such sleeping devices visible on the network so you know they’re available.

The patent’s inventor is Stuart Cheshire, who also invented Bonjour, Apple’s implementation of Zeroconf. This is probably no accident, since Bonjour seems a good fit for such a network service. You might even say it was designed to enable lightweight protocols like these.

In this case, the sleep proxy might use Bonjour to find power-saving devices on the network, then ask the devices for the particulars on how to wake them. The devices announce to the network that they’re going to sleep, which the proxy then detects, allowing it to pose as the sleeping device while it sleeps.

This innovation is certainly welcome, but what’s especially delightful is that Apple thought to solve the problem and had Bonjour ready and waiting.

Thursday, February 14th, 2008, 12:43 am    Trackback.