PEEKS AND POKES: Error tracking in FSI Viewer using HttpFox

When FSI Viewer is not working properly, and everything seems to be configured correctly, one wonders what is the cause FSI Viewer stalls.

Quite often certain GET requests that FSI Viewer is sending to the imageserver fail for different reasons. Misspelled configuration files and wrong permissions are among the causes for this. So we need to make visible what is happening in FSI Viewer.

There is a quite popular plugin available for Mozilla Firefox, called HttpFox. If you don’t happen to have Firefox installed, first download it from and install it.

If you have Firefox installed, please add the HttpFox Plugin, which can be found at

After restarting your browser you will see a new entry in your Extras menu of Firefox. Please choose Extras -> HttpFox -> Open in own window

At the top left click the start button and then open the bogus FSI Viewer URL in your browser. You will see all the requests that get send in HttpFox.

Now check if any requests fails for a missing file (404) or if any server errors occur (403/500)
You can also see whether FSI Viewer tries to load the crossdomain.xml.
Rightclicking the URL in the list lets you copy the request to the clipboard. You can paste it in your browser and look at the Sourcecode to verify correct XML result for list requests.

Firefox HttpFox Add-on

Thus HttpFox helps tremendously tracking down errors and bugs in your setup and is highly recommended for any user.