The error on Heroku and the MS Edge stuff I mentioned are separate things.  Please don't mix them up.  The error with Heroku when it can't get my server app to bind to any ports is a 404 Not Found error and in the browser it shows Heroku's own custom error page.  

When I said that about running the app and visiting the browser, I wasn't talking about Dockerfiles and Heroku, I was talking about just running the server app by itself on my computer.  Right now that's what I have to get to work first.  I'll try using a Dockerfile for it again after the port binding issue is fixed.