You need to port-forward your server.
To do this you need go into your browser, punch in 192.168.1.1 Enter the username/pass
Look for the port forwarding part of your router. There might be something called range port-forwarding and Single Port forwarding. In both of those. This can vary from router to router. Basically you put in your Computers 'Local IP' and put the opening and closing ports at 7756-7756
Then go into the PureFaction server launcher, go into the settings for your DM server, punch in 7756 into the Server Port
And Launch Server.
Now of course if you want to play that server on the same computer make sure your PF Clients Port is not set to 7756
If you don't know how to do all the technical stuff,
Youtube - How to find my computers 'Local IP'
Google - how to port forward "your Routers Model" - then subsequently hope you find a Youtube Video.
Hope this helps, it took me a long time to figure it out. Then I just Google'd a few things...
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