Can you access the server from other computers on your network?
Make sure there's not a local firewall blocking it by default - if you're on windows try disabling the windows firewall then either get your friends to try again or use a port checker (http://www.canyouseeme.org/) while the server's running to test it. If that
works, re-enable the firewall and add an exception for the right port.
Another thing to check, if you're using DHCP instead of a static local IP, is that your local address hasn't changed since you set up the port forward - you won't get too far if the router's routing all those EO packets to an address which doesn't exist ^^