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 29000Trying 10.168.66.118...Connected to localhost.Escape character is ‘^]‘.^]telnet> quitConnection closed. 

source: https://www.jianshu.com/p/a9443e099b63