title: what type of message can a websocket send?
body: <p>I am trying to use a websocket to send audio message, what type of message should I change the audio stream into so that I can use a socket to send? 
  If I directly use a websocket.send(audio), I would get an error "DOMException", should I change it into binary data? and how?
  I am totally new to program, so please help!!!</p>