I have fully functional Rails 4 apps that run fine separately on the same MBPro, but if I have both running at the same time with a user logged into both, the last one where a user logs in, causes the other app's logged in user session to expire and I'm back at the login screen for that app. I am using Devise.
The rails start command I am using is:
rails s -p 3001 -b 0.0.0.0
rails s -p 3000 -b 0.0.0.0