What is the advantage of having a domain name (spotilocal) that resolves to 127.0.0.1?
Not sure if this is best suited to Programmers, Server Fault or Stack Overflow. It's not, however, a question about developing for Facebook.
Facebook recently announced tighter integration with Spotify. Play/pause buttons that control the Spotify desktop software have been added to Facebook, and the most recent version of the Spotify client runs a local web server. Facebook makes calls to, for example:
http://1234.spotilocal.com:4380/remote/status.json
http://1234.spotilocal.com:4380/remote/play.json
http://1234.spotilocal.com:4380/remote/pause.json
...where *.spotilocal.com resolves to 127.0.0.1.
What is the advantage of having a domain name that resolves to localhost? Is it so that Spotify can quickly make a code change on that domain name if something should break, and so don't have to rely on Facebook?
It seems Facebook could just as easily point to:
http://127.0.0.1:4380/remote/status.json
Answer
the biggest reason for us when designing it was so that it would work with https without a mixed-content warning. Getting a cert for a real domain is a lot easier than getting one for 127.0.0.1.