1·在启动knockd之前，关闭端口22960并尝试远程登录。
Before starting knockd, close port 22960 and try to log in remotely.
2·在这里，因为只希望打开或关闭端口22960，所以使用单一命令就够了。
In this case, because you just wanted to open or close port 22960, a single command sufficed.
3·因此，为了让计算机更安全，应该采取的第一个措施是把端口改为另一个不常用的非标准端口号，比如22960。
So, the first step you should take to make your machine more secure is simply to change the port to another unused and nonstandard port number-say, 22960.