什么是Httptunnel 作为一个实际的例子，我们下面来介绍一个在"非公开领域"使用的的通道软件，httptunnel。在httptunnel主页（请参阅参考资料）上有这么一端话， httptunnel creates a bidirectional virtual data connection tunnelled in HTTP requests. The HTTP requests can be sent via an HTTP proxy if so desired. This can be useful for users behind restrictive firewalls. If WWW access is allowed through a HTTP proxy, it's possible to use httptunnel and, say, telnet or PPP to connect to a computer outside the firewall.
Ok,server以及client端都启动了，我们可以开始我们的"通道"试验了，在client.yiming.com上执行一下如下命令看看： Client.yiming.com#telnet localhost 1234 Trying 0.0.0.0... Connected to 0. Escape character is '^]'. SunOS 5.7 This is yiming's private box! Any question,contact me with yiming@security.zz.ha.cn login:
看到B机的登录提示符了,输入账号密码看看是否工作正常？ Login:yiming PassWord: (omit here;) ) sever.yiming.com# ls bak check go httpd lost+found mrtg run soft wg
OK! 工作正常，和正常的telnet没有什么差别。
仔细观察整个过程，会发现在最开始的地方显示的是Trying 0.0.0.0...，Connected to 0.而不是Trying server.yiming.com…,Connect to server.yiming.com，这就很直观的可以看出来client端是转发1234数据包到本机80端口的。（然后再转发到远端）而不是直接连接远端的B机。
