Applications (games, torrent client programs etc) usually need to be set up as exceptions within the modem itself to allow incoming traffic (high speed transmission of data) specific to that application.

If you are using a "Gateway" model type modem from Telstra and you are on adsl access and above (not cable) you can access the modem settings by typing the following into your browser address bar:

10.0.0.138

and then entering your NR account number username and password to acess the modem settings. If you don't know these or have access to them you will need to contact Telstra to verify yourself and they will give them to you.

Once inside the modem settings there is an easy to follow menu which shows all the options available. One of them is gaming/sharing applications under the Toolbox main menu. The game itself will need to be added to the list of applications and manually assigned a port number to access.

Let us know how it goes and if it fixes the problem.

Good luck with it.