Writing protobuf message to a websocket

I’m interested in writing a server process in julia that will periodically publish protocol buffer messages over a web socket. I’ve done a little naive experimenting, and haven’t gotten very far (did manage to get an error saying that the websocket implementation I was using didn’t support binary data). There seem to be at least 3 different packages that provide websockets: WebSockets.jl, SimpleSockets.jl and HTTP.jl. My inclination is to use HTTP.jl - is this misguided? For that matter, is my attempt to send protobuf content over a websocket misguided?