Turning of a physical object, like a light bulb (on or off) requires two things: an actuator, to open and close the physical electricity path, and a signal to initiate the actuator. This is like a relay with a state, either normally open or normally closed. If you wish to power cycle a computer you would want the relay in a normally close state so power is always running to the box. Then initiate an open signal to the relay. Normally this is a voltage that energizes the relay magnet and pulls the circuit arm in some direction. If the status is normally closed the application of energizer voltage will open the relay, shutting off power to the box. It will stay in this state until the energizer voltage is removed and the relay is reset to a normally closed state. So now you have to run a circuit, connect a power supply etc. to manipulate the actuator or relay. X10 devices handle the signaling "in band" meaning on the power circuit so extra wires and connections aren't necessary. Why won't X10 work..??. it's a standard language that can be manipulated as far as I can tell, and it's cheap. You can get the language off the internet and build your own app.?? X10 is a simple rudimentary language.

This thing could get quite complicated if you want to build a system yourself. I wouldn't do anything via parallel port. R2-232 and R2-422 on a serial connection are easier or as stated, get a card with various voltage outputs and tie those to a relay and then tie your device to the relay.

Another option is to build an app to monitor the serial port and when it sees a certain ASCII combo, the application could initiate a windows or Linux shutdown. But you are not physically removing the power in this case.


//EDIT trying to find some real world example. This guy wrote a program to control lights over a web page!!! http://www.x10.crevier.org/webinterface/

http://sourceforge.net/projects/wish *This linux project has caught my interest.