Google App Engine Localhost from Parallels

This post is for developers using a MAC, developing on the Google App Engine platform, attempting to connect to their development environment from Windows on Parallels to test browser compatibility.

NOTE: This post was updated on March 25th, 2013 to accommodate changes made to the GAE Python Development Server.

Again, you are:
1. Developing on a MAC.
2. Atop of Google App Engine
3. Using Parallels for browser testing

Setup:
1. On your MAC, open Google App Engine's Launcher application
2. Double click on the project you're attempting to connect to
3. In the "Extra Flags" field, enter "--host=0.0.0.0" (without the quotes) and hit the "Update" button.
4. Make sure the Windows firewall is OFF in your Parallels Windows instance.

That's it, open a browser in your Parallels Windows instance and hit the local network IP address of your MAC using the port delegation from Google App Engine launcher. For instance, if your MAC's IP address is 192.168.0.2, and your project's Google App Engine port is 8101, the address you put in your Parallels browser may be http://192.168.0.2:8101.

Voila.