Firewalls and routers block protocols, and then they get around by using web server proxy apps.
Basic installation guide for Windows PowerShell Web Access - Windows PowerShell Blog - Site Home - MSDN Blogs
"Windows PowerShell Web Access is a new feature in Windows Server 2012. It is an IIS application that provides a Windows PowerShell console in a web browser. The IIS application acts as a gateway between the web browser and the machines that you can connect to in your environment. These machines should have Windows PowerShell remoting enabled."