code: public void didSendMessage(final String message, final Date timestamp) {
          new Handler(Looper.getMainLooper()).post(new Runnable() {
              @Override
              public void run() {
                  if (null != listenerReference) {
                      Listener listener = listenerReference.get();
                      if (null != listener) {
                          listener.onMessage(message, timestamp, RespokeEndpoint.this, true);
                      }
                  }
              }
          });
      }
docs: Process a sent message. This is used internally to the SDK and should not be called directly by your client application.
  
  @param message The body of the message
  @param timestamp The message timestamp