The Gun library doesn't have a full 2.0 release yet, so we depend on :grcp_gun 2.0.1 for now. This is the same as :gun 2.0.0-rc.2, but Hex doesn't let us depend on RC versions for releases. Generate Elixir code from the proto file as protobuf-elixir shows(especially the gRPC Support section). Implement the server-side code and remember to return the expected message types. You can start the gRPC server as a supervised process. First, add GRPC.Server.Supervisor to your supervision tree.