You guys probably know that Visual Studio includes a lightweight ASP.NET development server which is an enhanced version of Cassini.
You may have noticed or heard, people want to change the port number of it so here we go;
1. Rigth click your website in Solution Explorer window and select Properties from the context menu (Alt + Enter).
2. Select the Web tab as shown on the picture.
3. In the Servers section check the Specific Port radio button and set it to your preferred port number.
4. Launch the Website to see if it matches the value you specified.
If you use an earlier version of Visual Studio it can be little different.
e.g. You may want to change the port number in the Properties (F4) window:
1. Having the Properties window open (F4) LEFT-click the website in Solution Explorer.
2. Find the Developer Web Server section and change the “Use dynamic ports” to False.
3. Specify the port number.
4. Start debugging (F5) to see if it matches the new port number.