Find your router’s local IP address
Log in to your router’s admin page
Locate the Port Forwarding, Virtual Server, or NAT section
Reserve a static local IP for the computer running the Minecraft server
Open the Minecraft server port in your firewall
Identify the server port used by your modded Minecraft server
Add a new port forwarding rule for that port
Set the protocol to TCP, or TCP/UDP if required by your router
Enter the static local IP of the server computer
Enter the external and internal port numbers as the same value
Save the router settings
Restart the router if needed
Start the modded Minecraft server
Share your public IP address with players
Test the connection from outside your local network
Use a dynamic DNS service if your public IP changes often