How to establish 2-way communication between a web server and a site server?

Question

I am planning a SaaS system, to be written in C#, ASP.NET using WCF that has two separate components:

1. On a static IP web server in the cloud will be a web app,

Answer 1

In the end I decided to go with NetTcpBinding, for reasons best given by @Allon Guralnek here. It's worth clicking through and reading what he has to say...