Port Forewarding Issue

I have successfully created a Minecraft server using a computer I have, and I am able to connect to the server using other computers on my network. However, my friends can't join my server, and it seems my port is closed. I made sure my port forwarding details were correct, and I made sure the port was getting through my anti-virus and firewall, but it still says it's closed. I've looked up quite a few different tutorials but they all have the same information. I'm at a loss of what to do, so any help would be appreciated.