Your browser does not seem to support JavaScript. As a result, your viewing experience will be diminished, and you have been placed in read-only mode.
Please download a browser that supports JavaScript, or enable it if it's disabled (i.e. NoScript).
举个简单例子，数据库假设只有服务器能连上，你本地电脑如何连接？就是这个隧道，让你先连上服务器，然后服务器转发数据库的端口