My problem was the same, but the solution had to do with changing a firewall setting. It turned out that node was set to block incoming traffic. I knew something was up because I used to be able to get to my localhost server from my phone.
Go to System Preferences -> Security & Privacy -> Firewall -> Firewall Options, and then scroll down until you find node and make sure node's setting is set to Allow incoming connections.
After changing the setting, I could reach the localhost server (port 3000) running on my Mac by going to http://192.168.1.11:3000