mac剑指丧心病狂，连最基本的telnet命令都没有，没办法，那我们就只能自己安装telnet命令了。
安装telnet前需要安装hongbrew，很简单，复制下面的命令到你的终端工具：
/usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
此时，在我的电脑上报了一个错，居然拒绝连接。。
Failed to connect to raw.githubusercontent.com port 443: Connection refused
这时，解决办法也很简单，就是配置一个代理，把下面的内容配置到你的host中即可解决。
199.232.28.133 raw.githubusercontent.com
配置完之后，再运行刚才的命令，效果如下：
Warning: The Ruby Homebrew installer is now deprecated and has been rewritten in
Bash. Please migrate to the following command:
/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install.sh)"
==> This script will install:
/usr/local/bin/brew
/usr/local/share/doc/homebrew
/usr/local/share/man/man1/brew.1
/usr/local/share/zsh/site-functions/_brew
/usr/local/etc/bash_completion.d/brew
/usr/local/Homebrew
Press RETURN to continue or any other key to abort
==> Downloading and installing Homebrew...
remote: Enumerating objects: 47, done.
remote: Counting objects: 100% (47/47), done.
remote: Compressing objects: 100% (47/47), done.
Receiving objects: 63% (87846/137462), 25.03 MiB | 26.00 KiB/s
好了，等brew安装完成之后，接着用如下命令安装telnet就大功告成了。
brew install telnet
