ERR_CONNECTION_REFUSED in production

[hypo-thesis]

I have a code here that supposed to send a youtube link back to the server side process it and then let the user download the file which is stored at https://github.com/hypo-thesis/yt

It works well locally but in production when I access it through domain name it gives me net::ERR_CONNECTION_REFUSED
Here is the screenshot of the error.

How can resolve this?