RPC/IPC protocol designed for distributed UNIX daemons.
The M.A.R.T.Y. Middleware Protocol is a framework for all of the M.A.R.T.Y. bundled applications to communicate with each other. Note that it is a messaging protocol, not a file transfer protocol. As such, it does not necessarily care about supporting completely arbitrary payloads, although it is designed in such a way that arbitrary payloads are possible with various encoding methods.
The latest version of the specification is 2.0, which can be found below: