Try Googling "X10 and Ethernet", or "X10 and TCP IP".
RXCOM makes a RF to ethernet box which can pick up RF transmissions of X10 RF devices (USA or Euro frequencies) like motion sensors and hand held remote controls. But that is only half of the equation. You still need a TCP to X10 translation. I don't know what software is out there to accomplish that. Again
Google is your friend. I do know Homeseer automation software
http://www.homeseer.com/ has plug-ins for RXCOM devices. Homeseer can interface to X10 powerline controls through several interfaces like the CM15A and CM11A from X10, or ACT's TI103, etc.