Today I ran into a problem: Via the SharePoint search I got some results returned, including a pathName to it's default zone. This zone was used for indexing the sites, but isn't accessible as a production URL due to authentication issues. One solution was to remove the default zone and replace it by the public url via a replace function, but that method of course isn't failsafe in the future (what if the public url changes??)
Gladly, SharePoint has a neat little function delivered in the SPUtitlity class:
SPUtility.AlternateServerUrlFromHttpRequestUrl(Uri url)
Life is great when having a Utility class ;)