How do I parse the domain name out of a URL?

This has come up several times. People have complex URLs with querystring parameters and different protocols (e.g. http:// and https://) stored in a database, flat file, or user-entered, and they want to return just the domain name portion of the URL. Split() is a wonderful function: 
 

<%      Function ParseDomainFromURL(url)          urlParts = split(url,"/")          ParseDomainFromURL = urlParts(2)      End Function        complexURL = "http://foo.com/whatever.asp?foo=1&bar=2"      domain = parseDomainFromURL(complexURL)      response.write "Domain = <b>" & domain & "</b>"  %>

 
This function assumes that you are going to pass a valid URL, with a // preceding the domain name. You can check for this first by testing within the function: 
 

<%      Function ParseDomainFromURL(url)          if instr(url, "//") > 0 then              urlParts = split(url,"/")              ParseDomainFromURL = urlParts(2)          else              ParseDomainFromURL = "Invalid URL"          end if      End Function  %>

 
Note that we don't use a split on the double // character sequence, because splitting on single / allows us to isolate just the domain name in one step, and also allows us to avoid having to special-case the scenario where the URL doesn't have any other slashes (e.g. 'http://www.foo.com').