How to get Url Port for Rails instance without request/response loop?

Is there a way to get the url/port that the current rails app is running on without using the http 开发者_如何学JAVArequest/response loop?

Or a way to invoke a request to self from within a rails app that will spawn the correct request object to get the url/port?

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env["SERVER_PORT"]

Would using this environment variable work?