canyouseeme.org is a great free port checking tool to check if ports are opened and forwarded correctly. If items are not opened in the firewall, if the ISP is blocking it, or whatever may prohibit certain ports traffic, this tool helps find it. Go to the website from inside the network you wish to test, go to this website, and enter the ports you'd like to test. It will tell you if the port is blocked or hitting a dead end.