James Munns: I've been test more with your RPC library and I have hit one snag you probably have thought about.  :)

When doing `send_resp` over a lossy channel, the response might get lost and we need to retry.
However everytime I use `send_resp` the sequence number counts up so the embedded device cannot know if it's a retry of an old sequence number or an actual new RPC.
To me it feels like `send_resp` might need a bit more state to allow for retries, what do you think?