I've been struggling for a while trying to run something on iis-express (service for example) and trying to use it from another device, for example, trying to debug Andoroid\IOS\Win-Phone (or Xamarin) application with WebApi\WCF service.
I have encountered many problems while trying to do this, I've found lots of recommendations about what to do, but non of them worked for me and were to complicated if you don't have a static IP.
After a while, I've found this very simple node.js open source iis-express, So I wanted save everybody lots of time
This app just opens a simple temp proxy to a specific port on iis-express, it works great and it is very simple.
Just install it with npm:
npm install -g iisexpress-proxy
And then run
iisexpress-proxy localPort to proxyPort
Just don't forget to install node.js and make sure ports are not blocked by firewall
Hope it helps