telnet测试端口是否可用以及退出

#telnet ip port
#出现Escape character is '^]'.说明成功
#ctrl + ]  后q退出
$ telnet 127.0.0.1 80
Trying 127.0.0.1...
Connected to 127.0.0.1.
Escape character is '^]'.
^]
telnet> q
Connection closed.