Gareth Jones

Lately I’ve been doing some work (I promise it is real work) with Battlefield 2. The server part of the game has a cut-down version of Python built in so that you can interact with it, modifying aspects of the game and reacting to events etc. More details on this can be found on this wiki.

Anyway, the Python version it uses is pretty old (2.3.4, current version is 2.5.2) and it’s had functionality cut, e.g. no threading support. For the work I’m doing I needed threading support and a few other things so wanted to swap out the version of Python for another - turns out this wasn’t obvious so here are the steps:

1. Replace the Battlefield 2 Python library (e.g. ‘bf2/bin/ia-32/libdice_py.so’) with the version of your choice. I just linked to my locally installed version ‘/usr/lib/libpython2.5.so’.
2. Replace the Python library path at runtime to use the new libraries, e.g. edit ‘bf2/python/bf2/__init__.py’ and putting the equivalent of ’sys.path = ['/usr/lib/python2.5/', '/usr/lib/python2.5/lib-dynload/', 'python', 'mods/bf2/python', 'admin']‘ after the ‘import sys’ line.

I do get the following warning at runtime: ’sys:1: RuntimeWarning: Python C API version mismatch for module host: This Python has API version 1013, module host has version 1012.’ but it doesn’t seem to cause any problems (so far!).

Ok, so I got a bit bored at some point over Christmas and decided to play with one of my presents - a USB Rocket Launcher.

The first difficulty was getting it to run on my Linux laptop as the drivers were only for Windows. A quick search and Scott Weston sorted me out. Then I thought it should really be controlled by more than just the keyboard so I hooked it into the Thinkpad accelerometer - now movements of the laptop could direct it. Finally, as I knew Andy Stanford-Clark would be a bit disappointed in me if I hadn’t, I MQTT‘d it so that the accelerometer details are published to a broker, a bridge app subscribes to that info and (where appropriate) publishes commands which are received by a final subscriber that actually sends the commands to the rocket launcher. This way you can easily swap out the accelerometer or indeed rocket launcher for something completely different.

I feel quite pleased with myself and slightly ashamed at the same time.