Wednesday 3 August 2011

Simple rate limited HTTP server for testing HTML5 media/streaming

While working on the Firefox HTML5 video and audio support, I've found it extremely useful to have an HTTP server on which the transfer rate is reliably limited. Existing servers are either too heavy weight, like apache, or have inconsistent rate-limiting, like lighttpd which I found to have very "bursty" rate limiting.

I ended up taking the educational route, and implementing a simple HTTP server in C++. It supports the following features:

  1. Support for HTTP1.1 Byte Range Requests. This means you can seek into unbuffered data when watching HTML5 video.
  2. Rate limiting, configurable on a per request basis by passing the "rate=x" HTTP query parameter, where x is the transfer rate of the connection in kilobytes per second. The server will send x/10 KB ten times per second to maintain this rate smoothly.
  3. Simulated live streaming, configurable on a request basis by passing the "live" query parameter. When in "live" mode, no Content-Length header is sent, and the server doesn't advertise or perform byte range requests - so you can't seek into unbuffered video/audio, just like in a live stream.
  4. Cross platform; tested on Windows (runs on port 80) and Linux (runs on port 8080). I haven't test it on MacOS yet.
  5. Simply serves all files in the program's working directory, making it easy to use (and abuse).
  6. Open source! Get the code at, or download a pre-built win32 binary.
For example, if you wanted to simulate a live stream being served at 100KB/s, your test URL might look something like http://localhost:80/video.ogg?rate=100&live.

I've been using it for quite a while, and over the weekend I finally cleaned it up and put it up on GitHub. Check it out.


silvia said...

This is awesome. Would love to use it to experiment with HTTP adaptive streaming approaches! (If only there was time...)

Justin Dolske said...

Nice. I did a similiar little hack with just PHP a while back...