How to test a Facebook application on Google App Engine locally (code 191 error)?

I want to test and develop locally, while having the application on the air, and I'd rather not use two separate application id's because this means I have to change the code every time I deploy a new version and then change it back.

I understand that I can change the host file so that localdev.{{my application URL}} would refer to localhost and the URL will be valid, so I won't get the 191 code, but the Google App Engine launcher forces me to use port 8080, and this can't be defined in the host files. If I try to enter localdev.{{my application URL}}:8080 I get the 191 error code again.

Is there any way to use port 80 with the Google App Engine launcher?

Or is there another solution?

UPDATES:

1. I managed to run locally on port 80 by using the Python file from the Google App Engine directory and not the Google App Engine launcher GUI. However, Facebook doesn't recognize localdev.{{my application URL}} as the URL, and it still gives me the same error code, 191.

2. Once I changed the host file into {{my applicatio开发者_如何转开发n URL}} without the "localdev." it worked, so this must mean the URLs must match exactly, and not just the domain. Is this true? Anyway, it isn't optimal, because it means I have to change the host file all the time, but it's something you can live with...

I have 2 Facebook apps, one with my real URL (for production), and one with http://127.0.0.1/ (for development). Then I have a utility function in my code which checks self.request.host, and selects the appropriate app id and secret.

The reason I use http://127.0.0.1/ and not http://localhost/ or http://localhost:8080/ is that I found only http://127.0.0.1/ would work in Internet Explorer (other browsers seemed fine with those other two URLs, provided they matched the Facebook app).