Sending data between boards

Coming soon

This isn't here yet. It's listed so you know it's planned.

Data travels between boards as structs: plain data with numbered fields, never a live object.

Each field's number is what crosses the network, not its name, so a board still running an older program can read what a newer one sends, and the other way round. A field the reader doesn't know about is skipped, and one the sender didn't have takes its default.