Testing GWT Application in Virtual Machine

I am developing on a Mac, but to test my GWT applications for cross-browser compatibility in Internet Explorer I need to use Windows, thus I got Windows 7 installed using Parallels. Just by the way, to be able to test in different Internet Explorer version, I am using a pretty handy application called IETester.
But trying to access localhost with IE in the virtual machine did not work. I got a “404 page not found” error instead of seeing my app running on the local App Engine instance. Obviously, Parallels does not automatically forward localhost requests to OSX and maybe that is actually a good idea security-wise.
To fix the issue, you need to run Google App Engine on a public network interface, or in other words, bind the App Engine server to all available IP addresses. The down side: everybody knowing your IP address can see the GWT app now, but otherwise you are not allowed to access it in the virutal machine as from your OSX’s point of view, that Windows machine is “some other guy accessing from the outside”, too. To make GAE accessible from the outside, add the parameter “-bindAddress” when launching you local GAE. Using Eclipse you can achieve that by right clicking your project -> Run As -> Run Configurations -> Choose “(x)= Arguments” tab; add the option to the top most box titled “Program arguments” in the options area (e.g. before “-port 8888”).

The first part of the list of arguments should look something like that:

-remoteUI "${gwt_remote_ui_server_port}:${unique_id}" -startupUrl GlocalUiPg2.html -logLevel INFO -codeServerPort 9997 -bindAddress -port 8888 ...

Now, you can access you app using the OSX’s public IP address. (You can get to know your IP by having a look at the network preferences panel.) Launching GAE from Eclipse, you will see a different link (URL) in the “Development Mode” tab now, containing the public IP already. Using that one in, say, your Firefox on Mac, it will ask you now whether you want to allow the debugger access. That is also due to the fact, that you are now using a public address, so it is not clear to your local debug server, whether that request came from the same computer or someone else in the network.