I've also developed a strikingly similar low latency real-time IPC message bus for work. It also uses sockets with transparent shared memory optimization. In my case, it's the backbone for an autonomous aircraft's avionics. I made everything agnostic to the message scheme, though, and most of the tooling supports an in-house schema, protobuf, JSON, YAML, etc. There's also clients implemented in C++, Rust, Python and Julia.

What troubles has protobuf caused you?