To enable wake-on-LAN over the Internet, the open hardware platform Arduino is used.
Not all routers support wake-on-LAN from the Internet to LAN. This depends on whether you can configure the ARP cache and send or forward a WOL broadcast package.
To support WOL, in this case on an Apple TimeCapsule, an Arduino Ethernet Pro board is used. Thus having a low-power device (Arduino) listening for WOL.
Both the Arduino board and machine to wake-up are connected via Ethernet to the TimeCapsule. The Arduino is powered using the TimeCapsule USB port.