First, no one other than you SHOULD be able to connect to the sql server. You can have it firewalled and MaNGOS will still run perfectly. So you are debugging the wrong problem. As long as MaNGOS can connect to your SQL server, which should be running on the localhost anyway, people can connect if you have configured the realm database properly. If no one can connect either your DB is improperly configured, your giving the wrong IP out, your firewalled, or you havn't forwarded your ports to your router. Lastly, you COULD have a version of server that will not allow incoming connections.