Issue Node JS NGINX Directive

[lukegalea16]

I have a Node JS app which listens on port 5683. I have opened the appropriate Firewall port and added the nginx directive 'listen 5683;' to the particular subdomain. However the plesk support team said that said directive is not needed. When removing this directive, the app stops responding to requests on port 5683 however.

What should I do?
Thank you
Luke