很多时候 telnet 完就无法退出了，ctrl+c 有时也无法退出
后来找到了正确的命令 ctrl+] 然后在telnet 命令行输入 quit 就可以退出了
telnet 10.168.66.118
Trying 10.168.66.118...
Connected to localhost.
Escape character is '^]'.
^]
telnet> quit
Connection closed.
source: https://www.jianshu.com/p/a9443e099b63