Log in to your router’s admin page
Find the Port Forwarding, Virtual Server, or NAT section
Note the local IP address of the device you want to reach
Reserve or set a static local IP for that device
Choose the protocol required by the service: TCP, UDP, or both
Enter the external port or port range
Enter the internal port or port range
Enter the device’s local IP address
Save the rule
Apply or reboot the router if required
Allow the port through the device’s firewall
Test the port from outside your network
If it fails, check the router’s WAN IP for CGNAT or double NAT
If needed, place the modem/router in bridge mode or forward on the upstream device too