How to enable both http and https?

Hi there,

I have followed the guide described here to enable https. It all went well until for some reason we have to decide support http at the same time. It seems when https is enabled, the server will not listen on 80 according to

By default, when you specify an external_url starting with 'https', Nginx will no longer listen for unencrypted HTTP traffic on port 80.

Is there any way it can support both http and https, instead of redirecting http to https?

Thanks, Gan