如何临时解析本地端口的名称？

I develop websites with rails, and I was looking for a simple way to setup a dynamic name resolution for my app. The final product I need is to is: Every time I start a rails application (by typing rails server on my application folder, I want to run it on a random port and if I type the application name on my browser (like myapp.dev or something) it resolves to the localhost on the correct port.I develop websites with rails, and I was lookin