Why would discourse want to connect to port 3000

[Stephen]

Is this related to your previous topic?

Discourse failing to connect to port 3000

After upgrading from 2.4.2 to 2.6.x discourse is no longer working for us. The issue is discourse is trying to connect to port 3000 on 127.0.0.1. I have rebuilt web_only numerous times with ./launcher rebuild web_only Questions. What is supposed to be running on 127.0.0.1:3000? How to restart that service? Cheers and thanks!