Espruino on ESP8266

I think getting ESP8266 actually working reliably with hardware peripheral support should really a priority before you start optimising

It's not because I ask about advanced features that I'm necessarily optimizing right now...

We could definitely add some kind of data_received and get_data_to_send callbacks at some point

I'm puzzled, isn't that what Socket.on('data' and Socket.on('drain' do?