John Smith's Blog

I've just uploaded a small personal project to GitHub here. It's basically a very crude webserver that allows me to share audio files on my Linux boxes to my iOS devices, using Mobile Safari.

The main reason for noting this is that the code may be of more general interest because it implements an improved version of Python stdlib's SimpleHTTPServer module, that implements basic support for the Range header in HTTP requests, which is necessary for Mobile Safari on some MP3 files.

During early development, I found that some MP3 files would refuse to play in Mobile Safari when served by SimpleHTTPServer. The same file would play fine if served by Apache. Because debugging mobile web browsers is a PITA (caveat: I've haven't kept up with the latest-and-greatest in this area), I ended up resorting to Wireshark to see what was going on.

Wireshark indicated that Mobile Safari would request chunks of the MP3 file (initially just the first couple of bytes), but SimpleHTTPServer would always serve the entire file, because it never checked for the existence of the Range header. On certain files, this wouldn't bother Mobile Safari, but on others it would cause the audio player widget to show an unhelpful generic error.

Once I understood what the problem was, I found that I'm not the first person to get caught out by this, and that Apple themselves state that servers need to support Range to keep Mobile Safari happy.

To solve the problem, I wrote a new class HTTPRangeRequestHandler that is a direct replacement for SimpleHTTPServer. In my app code proper, I then (try to) pull in my enhanced handler as follows: try: import HTTPRangeServer inherited_server = HTTPRangeServer.HTTPRangeRequestHandler except ImportError: logging.warning("Unable to import HTTPRangeServer, using stdlib's " + "SimpleHTTPServer") import SimpleHTTPServer inherited_server = SimpleHTTPServer.SimpleHTTPRequestHandler ... class MySpecificHandler(inherited_server): ... def main(port=12345): Handler = EnhancedRequestHandler httpd = SocketServer.TCPServer(("", port), Handler) Arguably it might be better for the code to die if HTTPRangeServer cannot be imported, but as the stdlib SimpleHTTPServer is good enough for many browser clients, it doesn't seem too unreasonable to use it as a fallback.

This code is currently OK for most uses, but currently it doesn't support all variations of the Range header as described at aforementioned W3C spec page. It does however support all the requests variants I've seen in my - admittedly very cursory - browser testing, and any requests that it can't parse will instead get the full file served, which is the same behaviour as SimpleHTTPServer.

The musicsharer application that's built on this class is even rougher, but as it's really just intended for my own personal use, you shouldn't hold your breath waiting for me to tart it up...

I've made public the code I use to render tweets to marked up HTML on the right-hand side of this blog. It's nothing special, either in terms of what it does or how it does it, but I've tried to be thorough at catching edge cases and doing sensible/useful things, so it might come in useful for someone? I was surprised that I couldn't see anything out there that already did this, but I didn't look especially hard, so maybe I have just reinvented the wheel.

The code is on GitHub at https://github.com/menboku/tweet2html. Licence is GPLv2.

I've just pushed memcachablehandler to GitHub, which is a small Python App Engine library to make it easy to memcache pages - or images, or anything else you might serve up - and re-serve them without having to regenerate them from a Django template or suchlike. This should speed up response times ever so slightly, and also maybe make things more reliable as well (based on my personal experience with the memcache vs datastore availability).

The library is a slightly-tweaked version of some of the code that I've had in this blog for the past few days, so hopefully it's not too buggy. I know I'm not the first to write something like this - see the README for a link to something similar - but maybe it could come in useful to someone else?

I don't currently have any plans to extend the functionality beyond what's already there, but anything that gets updated in this blog should get pushed into that repo in fairly short order. At some point I'll probably make this blog code public as well, but I want to get it in a much more polished state before daring to show it to the world :-)