The ability to serve multiple domains from a single Mac is perhaps the most commonly requested feature on mailing lists related to running Macintosh Web servers. Although various hacks and partial solutions do exist, Open Door Networks’ HomeDoor offers this feature by itself. A five-domain "lite" version of HomeDoor comes bundled with the Apple Internet Server Solution 2.0, with a special $249 upgrade to the full version, which normally costs $400.
If you haven’t the foggiest idea what a multihomed Web server might be, the basic situation is that multihoming enables a single Web server to respond to "http://www.companyX.com/" and "http://www.companyY.com/" with different default pages. Although it’s easy to assign companyX and companyY domains to a single Mac running a Web server, there hasn’t been any good way to coerce the Web server into serving different default pages for different domains.
Why would someone care about this feature? The answer boils down to the fact that if someone guesses at the URL to a Web site, they are likely to guess at "www", plus the company name, with ".com" at the end. (You can just type a company name into the Location field in Netscape 2.0, and Netscape will automatically guess that the URL is formed in that way.) If that Web site shares a server with another site that uses a different domain, it’s normally necessary to use some sort of shared default page that directs people to the right set of pages for each domain. But that’s not particularly slick, and a lingerie retailer might not want to share a default page with some monster truck dealer.
Previous Solutions — In the past, there have been a number of less-than-popular solutions to this problem. First, because it’s easy to serve pages from different servers, some people have set up something like a cheap Mac LC to serve just the home page for the second Web site. All subsequent files live on the main server, say a Power Mac 6150. That works, but requires a number of cheap Macs equal to the number of different Web sites you want to serve from the same Web server. Using multiple Macs works especially well if the different Web sites are equally popular, since the multiple Macs can help spread the load rather than concentrating it on a single machine.
Second, you can run multiple copies of your Web server, each using a different port number, but no one is likely to guess at a site’s custom port number correctly.
Third, since Unix can provide this multihoming capability, another solution has been to install Tenon’s MachTen, a flavor of Unix that runs on the Mac. Although this solution also works, it requires buying MachTen and dealing with Unix as well as the Unix httpd server, which isn’t a task for those who have never used Unix seriously.
HomeDoor — Now, however, HomeDoor provides multihoming without requiring any additional programs or machines. It sits at a low level of the Mac OS (Amanda Walker of InterCon postulated it essentially wraps the Ethernet driver) and accepts incoming requests for multiple domains, redirecting each one to a different default home page. There is a slight catch, though, because the location field in a Web browser doesn’t display the URL the user entered (the "clean" URL), but instead the URL to which HomeDoor redirected them (a "dirty" URL, because a Web browser typically reports the actual URL retrieved). The HomeDoor Users’ Guide contains a workaround that comes close to solving the problem. See the HomeDoor FAQ for more details.
HomeDoor has become a popular utility for Macintosh Web servers that want multiple virtual domains, but it’s not quite as clean as multihoming on Unix machines, where the returned URL isn’t "contaminated" in any way. For the moment, though, it’s the best solution available on a Macintosh.
Late Breaking News — Highware has released MultiHome, a $189 CGI for WebSTAR that provides multihoming capabilities. It requires the Web browsers used by users support "pushpull" and even with that, users see a page listing the domains served by MultiHome before they’re automatically shown the proper page. Also, as with HomeDoor, the URLs reported by the Web browsers are "contaminated" with a directory after the proper virtual domain.
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