Your node.js server is running on a port determined at the end of the script usually. Sometimes 3000. but can be anything. The correct way for others to access is as you say…
http://your.network.ip.address:port/
e.g.
http://192.168.0.3:3000
Check you have the correct port – and the IP address on the network – not the internet IP.
Otherwise, maybe the ports are being blocked by your router. Try using 8080 or 80 to get around this – otherwise re-configure your router.