在没有端口转发的Web服务器的情况下接收Github pubsub事件

如何解决在没有端口转发的Web服务器的情况下接收Github pubsub事件

我目前已编写以下代码：

public class Connector {
  public String auth;
  public static void main(String[] args) throws IOException,URISyntaxException {
    Connector c = new Connector();
    c.setAuthenticationToken( /* token */ );
    JsonObject o = new JsonObject();
    JsonObject hub = new JsonObject();
    hub.addProperty("mode","subscribe");
    hub.addProperty("topic","some_event");
    hub.addProperty("callback","my_public_IP:some_port");
    o.add("hub",hub);
    String request = o.toString();
    System.out.println(new GsonBuilder().setPrettyPrinting().create().toJson(new JsonParser().parse(c.writeJson("https://api.github.com/hub",REQUEST_METHOD.POST,request))));
  }
  public void setAuthenticationToken(String token) throws UnsupportedEncodingException {
    this.auth = "token " + token;
  }
  public String writeJson(String strUrl,REQUEST_METHOD method,String data) throws IOException {
    URL url = new URL(strUrl);
    HttpURLConnection con = (HttpURLConnection) url.openConnection();
    con.setRequestMethod(method.name());
    con.setRequestProperty("Accept","application/json");
    con.setRequestProperty("Content-Type","application/json; utf-8");
    con.setRequestProperty("Authorization",this.auth);
    con.setDoOutput(true);
    if (data != null) {
      try (OutputStream os = con.getOutputStream()) {
        byte[] input = data.getBytes("utf-8");
        os.write(input,input.length);
      } catch (IOException e) {
        e.printStackTrace();
      }
    }
    StringBuilder response = new StringBuilder();
    try {
      int statusCode = con.getResponseCode();
      InputStream is = null;
      if (statusCode >= 200 && statusCode < 400) {
        is = con.getInputStream();
      } else {
        is = con.getErrorStream();
      }
      BufferedReader br = new BufferedReader(new InputStreamReader(is));
      String responseLine = null;
      while ((responseLine = br.readLine()) != null) {
        response.append(responseLine.trim());
      }
    } catch (IOException e) {
      e.printStackTrace();
    }
    con.disconnect();
    return response.toString();
  }

打印以下响应：

{
  "message": "Invalid hub.callback: \u0027\u0027","documentation_url": "https://docs.github.com/rest/reference/repos#pubsubhubbub"
}

我的目标是打开一个WebSocket，让该WebSocket监听从GitHub发送的事件，而无需使用外部API来转发我网络上的任何端口。 如何指定未打开的ip:port的回调？ 有没有使用WebSocket的替代方法吗？ 是否可以创建到https://api.github.com/hub的传出连接，然后创建指向该传出连接的端口的Webhook，而无需转发该特定端口？