How to access Rails app on Mac from VMware Fusion Guest OS.

Virtual Machine > Network > NAT
*NAT is default setting.

On Mac.
System Preferences > Network
Check your IP address.

Then access http://your.ip.address:port_number(http://192.161.1:3000) from your Guest OS.
You may don't need to change your firewall settings.
You must include 'http://' on URL if on IE.