code: func ReadClientBinary(rw io.ReadWriter) ([]byte, error) {
  	p, _, err := readData(rw, ws.StateServerSide, ws.OpBinary)
  	return p, err
  }
docs: // ReadClientBinary reads next binary message from rw, considering that caller
  // represents server side. It is a shortcut for ReadData(rw, ws.StateServerSide).
  // It discards received text messages.
  //
  // Note this may handle and write control frames into the writer part of a given
  //  io.ReadWriter.