I cover this issue in detail in my book (http://slinnbooks.com/books/serverSide), with code examples and explanations. The book shows how to discover the originating domain and how to dynamically configure data services accordingly.
Mike > I've been writing some small programs that use HTTPService calls to > fetch data from a back-end. During testing, I'm using 127.0.0.1 or an > IP address on my subnet. When I deploy, I update the IP address in > service definitions to the right external address and build the app. > Or at least I mean to. It's all too easy to accidentally change the > addresses for internal testing and then forget to switch them back > before building. > > Is there a best practice or simple strategy for putting the IP address > somewhere outside of the source code that it can easily be edited > without a rebuild?

