[dbmikus]

To get feature parity, you still need an IDL to generate types/classes for multiple languages. You could use JSON Schema for that.

Websockets do not follow a request/reply semantics, so you'd have to write that yourself. I'd prefer not to write my own RPC protocol on top of websockets. That said, I'm sure there are some off the shelf frameworks out there, but do they have the same cross-language compatibility as protobuf + gRPC? I don't think "just use JSON with websockets" is such a simple suggestion.

Of course, gRPC does have some of its own problems. The in-browser support is not great (non-existent without a compatibility layer?) last time I checked.