您可以在与预期的不同的端口上运行守护进程，前提是您可以将这一变更传递给客户端。

You can run daemons on different ports other than what is expected as long as you can communicate this change to the clients.

youdao

注意，当这个守护进程停止运行时，系统是安全的；所有端口关闭，不可访问。

Note that in the case of a crash, your system will be safe; all ports will be closed and unaccessible.

youdao

现在，使用 sudo /etc/init.d/knockd start 或 sudo knockd -d 启动端口敲门守护进程（这两个命令是等效的），然后再试一下；

Now try that again after starting the port-knocking daemon by using sudo /etc/init.

youdao