https://blog.wongcw.com/2018/12/04/fsf-%e5%be%9ehandshake-%e7%8d%b2%e5%be%97%e4%b8%80%e7%99%be%e8%90%ac%e7%be%8e%e5%85%83%e6%8d%90%e6%ac%be/