If the sender is on the same subnet (local network, aka LAN) as the computer to be awakened there are generally no issues. When sending over the Internet, and in particular where a NAT (Network Address Translator) router, as typically deployed in most homes, is involved, special settings often need to be set. For example, in the router, the computer to be controlled needs to have a dedicated IP address assigned (aka a DHCP reservation). Also, since the controlled computer will be "sleeping" except for some electricity on to part of its LAN card, typically it will not be registered at the router as having an "active" IP lease.