Step 1: Find your router's ip address. If you don't know your router's ip address, press the tab above ^.^.
1. Press the windows button + R, the program "Run" should come up
2. Type in "cmd"
3. When your in the cmd program type "ipconfig"
4. Now find the ip next to the words "Default Gateway" and that is your router's ip address
Step 2: After you find your router's ip address go to your web browser and type the ip in.
Step 3: It should take you to your router site and it will ask you for a username and password. The username is usually admin and the password is password.
Step 4: Now once your in your router's site there should be a tab on the site that says "Port Forwarding/ Port Triggering.
Step 5: Click on the tab and then click "Add Custom Service"
Step 6: Type in the service name whatever you want, I named it "Minecraft"
Step 7: In the external ending and starting ports type in "25565
Step 8: In the internal ip address, which you can find by going to cmd and type in ipconfig again. Then look for the ip next to the words "Ipv4 Address"
Step 9: Then click apply after you're done filling all that out.
Step 10: Put your router's ip address as the server ip
Step 10: Give others your external ip address so they can connect to your server.(You can use the router's ip or your external ip and others HAVE to use the external ip)
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PS: This Isn't Telling You How To Make A Minecraft Server, It's How To Port Foward One.