ARPC is a GRPC-like library that supports file descriptor passing.

ARPC ships with a script, aprotoc, that works similar to Protobuf/GRPC's
protoc. It generates message and service bindings, taking a .proto file
as an input. Where ARPC differs from GRPC is that messages may contain
file descriptors. These file descriptors are passed on to the remote
side transparently. This makes ARPC useful for implementing privilege
separation between processes.

WWW: https://github.com/NuxiNL/arpc