Extending the File Server Example to Load and Run HTML, CSV, and JS(called from script in HTML)

Looks good!

About post - I've definitely had req.on('data') working fine, even for handling uploads of multiple files. Is your Espruino firmware up to date?

Do you just get no calls to it at all? Perhaps you could try POSTing from something like curl on your PC, just to make sure it's not something with the way you're POSTing from the web browser?

To be honest for simple on/off stuff I've just been encoding it on the URL (/set?light=on/off) and decoding it with url.parse - I don't think there are huge problems with that as long as POST is used?