code: protected void onMessage(final ArrayBuffer arrayBuffer) {
          if (arrayBuffer != null && arrayBuffer.byteLength() > 0) {
              final byte[] message = toByteArray(arrayBuffer);
              if (message.length > 0) {
                  postMessageEvent(message);
              }
          }
      }
docs: Invoked by native listener.
  
  @param arrayBuffer received binary frame.