"use or run dedicated, stand-alone equipment or servers from the Premises that provide network content or any other services to anyone outside of your Premises local area network (“Premises LAN”), also commonly referred to as public services or servers. Examples of prohibited equipment and servers include, but are not limited to, email, web hosting, file sharing, and proxy services and servers;"
https://www.xfinity.com/Corporate/Customers/Policies/HighSpe...
Just because you've been getting away with it doesn't mean the risk of having your account suspended isn't real or worth considering.