Setting up server access - ports? CORS?

My Ember app works great on the local computer. I can load the Ember page from another PC, and separately, the back end data using a browser (e.g. http://ift.tt/2wJyooj), but Ember cannot; it states ERR_CONNECTION_REFUSED and retrieves no data to populate the lists/dropdowns/etc with.

Initially I'd had a ton of trouble with PUT messages even on the local, and wound up setting up a CORS rule to try to enable everything, but even that's not working here.

What's going on? Why can't Ember get the data that the same browser, in another tab, has zero trouble with?