https://blog.wongcw.com/2018/10/12/shell%e8%84%9a%e6%9c%ac%e8%87%aa%e5%8a%a8%e6%89%a7%e8%a1%8ctelnet%e5%91%bd%e4%bb%a4%e5%b9%b6%e8%bf%94%e5%9b%9e%e7%bb%93%e6%9e%9c/