There aren't too many things that would block outside players from connecting. Make sure you have ports 9000, 7000-7100 and 5998 all Port Range forwarded on your router to point to the server you IP you are running (192.168.1.100 or something like that). The other common reason is if you set this part of the config, which you shouldn't be setting:
Code:
<!-- Only specify these two if you really think you need to. (read: You don't) -->
<address>some.server.com</address>
<localaddress>192.168.0.1</localaddress>
Remove that section of the config from your config file if you aren't sure about how to comment it out. But, to comment it out, you would just need to make sure it looks like this:
Code:
<!-- Only specify these two if you really think you need to. (read: You don't) -->
<!-- <address>some.server.com</address> -->
<!-- <localaddress>192.168.0.1</localaddress> -->
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