How does Visual Studio decide which port to run applications on?

By default, ASP.NET Web Application Projects are configured to launch and run using the built-in VS Web Server (aka Cassini) on a random HTTP port on the machine.

This port number can be changed if this port is already in use, or if you want to specifically test and run using a different number:

_{(source: scottgu.com)}

I know this is a little bit old, but I was wondering the same thing. I eventually found the answer for VS2005, but figured I'd share it with the stack overflow community.

1. Open your project
2. Click (not right click) on the name of the project in the solution explorer (that top, bolded line)
3. Hit f4 - this will bring up a properties panel
4. Change "Use dynamic ports" to False
5. Optionally change the Port number to whatever port you want to use

And you're done.