protobuf relies on external framing and exact buffer lengths to parse things
correctly. So let's provide that by sending a fixed-length Frame message
before every real message.
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Plain-text was useful for the initial implementation where the counterpart was
netcat but now that both parts are in place, protobuf is a much more
convenient system to handle a frequently-changing protocol.
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>