I’ve finally solved a vexing problem that has been affecting version checks for my software.

Basically, checking for updates inside of XRay and Zingg! asks my webserver for a .plist file which contains the latest versions of everything, along with a brief message. On the server, however, this is actually a PHP script which also stores the user’s system version – which is appended to the URL – into a small database.

Since I changed over to DreamHost, my server has been set to gzip everything it sends if the receiver is capable of decoding gzipped files. However, for some time – not sure when that changed – this has messed up my version checking, and users would get a “website was unreachable” error. I did get some reports about this every couple of months, but always had attributed it to a network glitch somewhere… until I tried it myself and got consistent errors.

I read the .plist file directly using +[NSDictionary dictionaryWithContentsOfURL:]. Some combination of Cocoa, php and server parameters now causes the result to be gzipped, and NSDictionary doesn’t understand that format. Anyway, once I figured it out, I had to find a way to turn gzipping off for this particular file only, as I can’t change all the old software versions that are out there.

So, for now, adding this statement at the front of the php part of the file solved it:

header('Content-Encoding: UTF-8');

Strangely enough, rfc2616 says:

The Internet Assigned Numbers Authority (IANA) acts as a registry for content-coding value tokens. Initially, the registry contains the following tokens:




identity The default (identity) encoding; the use of no transformation whatsoever. This content-coding is used only in the Accept- Encoding header, and SHOULD NOT be used in the Content-Encoding header.

…and that’s it. No “UTF-8” is mentioned, so why is it working now? I tried “identity” (before seeing the SHOULD NOT comment) and it had no effect at all. I suppose I should try to debug this on my local server adn see where the problem lies, but time is short…

I don’t plan to use this method in XRay II, so it’s not urgent. I’ll probably use Andy Matuschak‘s Sparkle, of which I’ve had good references.