Error handling for puck.js communication

You mean using the Puck.js library? (source at https://github.com/espruino/EspruinoWebTools/blob/master/puck.js)

I believe you can use Puck. /getConnection() to get the currently active connection (you can use Puck.connect if not) and then you can do connection.on('close', function(d) { ... }) on that?