You need a controller which will send commands over the power lines to your switch. I'm using the Insteon PowerLinc Controller with a Serial connection. This works with Windows and Mac. Windows has freeware easily found on Google.
Setup was easy. I plugged it into the wall outlet, plugged the serial connector to my PC, and that's it.
You need to download and install SDM SmartHome Device Manager
. Now, once you've installed this, you can start sending commands to the PLC (PowerLinc Controller).
Since I had a MacBook in another room, I installed SDM Socket Server
, which is freeware for Windows. This let me connect over TCP/IP from upstairs and send messages downstairs. Note: you need to edit a registry setting to make this software work with the Serial (COM1) port. HKEY_USERS\.DEFAULT\Software\Smarthome\SmarthomeDeviceManager
The port needed to be changed from USB4 to COM1.
Here are some various programs
you might also find useful.