Alvin, a coworker of mine raised an interesting point about the ASP.NET Development Server (previously named "Cassini") hours ago.
Forgive my ignorance but it seems that the said builtin server was constrained to be accessed only with localhost or 127.0.0.1 and [more]would not work when using your IP (non loopback) nor machine name.
For IE you get : Internet Explorer cannot display the webpage
For Firefox : Unable to connect. Firefox can't establish a connection to the server at 192.168.1.xxx:PPPP (port number). The page title appears as Problem loading page
Not much there but if you use Fiddler you would see that it is returning an HTTP Error 500 which refers to "Bad Gateway".
Somehow that tells me, it's not your code but something with the server or the machine.
Looking around this is what I found.
Furthermore, from Web Servers in Visual Web Developer link you will find:
If you cannot or do not want to use IIS as your Web server, you can
still test your ASP.NET pages by using the ASP.NET Development Server.
The ASP.NET Development Server, which is included with Visual Web
Developer, is a Web server that runs locally on Windows operating
systems, including Windows XP Home Edition. It is specifically built to
serve, or run, ASP.NET Web pages under the local host scenario
(browsing from the same computer as the Web server). In other words,
the ASP.NET Development Server will serve pages to browser requests on
the local computer. It will not serve pages to another computer.
Additionally, it will not serve files that are outside of the
application scope. The ASP.NET Development Server provides an efficient
way to test pages locally before you publish the pages to a production
server running IIS.
Although it may seem that accessing the site from the same machine but using your IP would seem like accessing it locally, it doesn't seem to be the case. Could be that technically it would go out of your local machine first then, find which machine the IP points to so effectively it's being accessed externally already (sorry can't explain better than that). What's interesting though is that accessing the machine results in the same behavior for some reason. Maybe someone can clear it up for us. Or maybe Cassini is accessible this way and I'm just missing something.
Anyways, might seem pretty obvious but for those of us who haven't known this before then that's something to add to our knowledge base (or if I'm missing something, at least something to spark your curiousity)
One last thing, for those who wish to specify a specific port to use with ASP.NET Development Server here's a link : How to: Specify a Port for the ASP.NET Development Server