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
  @Override public synchronized void onOpen(WebSocket webSocket, Response response) {
    System.out.println("onOpen: " + response);

          .build();

      OkHttpClient clientForCall;
      if (i == 2) {
        // Force this request's response to be written to the cache. This way, subsequent responses
        // can be read from the cache.
        System.out.println("Force cache: true");
        clientForCall = client.newBuilder()
            .addNetworkInterceptor(REWRITE_CACHE_CONTROL_INTERCEPTOR)
            .build();
      } else {

    }
  }

  public static void main(String... args) throws Exception {
    new RequestBodyCompression().run();
  }

  /** This interceptor compresses the HTTP request body. Many webservers can't handle this! */
  static class GzipRequestInterceptor implements Interceptor {
    @Override public Response intercept(Chain chain) throws IOException {
      Request originalRequest = chain.request();