// Buffers sent on out can not be referenced once sent.
	StreamHandlerFn func(ctx context.Context, payload []byte, in <-chan []byte, out chan<- []byte) *RemoteErr

	// StreamHandler handles fully bidirectional streams,
	// There is flow control in both directions.
	StreamHandler struct {
		// Handle an incoming request. Initial payload is sent.
		// Additional input packets (if any) are streamed to request.