this.slackApi = slackApi;
  }

  public void open(String accessToken) throws IOException {
    if (webSocket != null) throw new IllegalStateException();

    RtmStartResponse rtmStartResponse = slackApi.rtmStart(accessToken);
    webSocket = slackApi.rtm(rtmStartResponse.url, this);
  }

  // TODO(jwilson): can I read the response body? Do I have to?
  //                the body from slack is a 0-byte-buffer