Why is my Rails 4.2 app not available on my local network?

Short answer: Change in 4.2. Specify --binding= when you start the rails server.


rails s -b

This was a change mentioned in the release notes:

3.3 Default Host for rails server

Due to a change in Rack, rails server now listens on localhost instead of by default. This should have minimal impact on the standard development workflow as both and http://localhost:3000 will continue to work as before on your own machine.

However, with this change you will no longer be able to access the Rails server from a different machine, for example if your development environment is in a virtual machine and you would like to access it from the host machine. In such cases, please start the server with rails server -b to restore the old behavior.

If you do this, be sure to configure your firewall properly such that only trusted machines on your network can access your development server.

Here’s a related discussion on the topic: