Surely a lot of that could be done with a commandline switch?

    tape_robot start -tapeid=1

as the quick hacky version, and:

    tape_robot --protobuf 'msg:start;tapeid:1'

(replace the 'single:quote;string:thing' with your protobuf message.), or

    tape_robot --protobuf_file filename

The filename could be a fifo or socket, of course. Then use a general purpose server which runs the programs:

    proto_serve tape_robot 127.0.0.1:8080

or whatever.

This (to me) is closer to the unix idea - one server program, one actual processing app. Why should my tape_robot program actually have a server embedded in it?

If in the future, I want to add authentication, I only have to add it (once) to the proto_serve program, rather than to every single application that is a 'server', for instance.

It would also allow a version which 'pre-forked' the processes, and left them waiting for the data on the socket/filehandle, or whatever.

You could do a bunch of this already using nc or similar, I suspect.