Every time I try to host a multiplayer game i get the message "No challenge value was received from the master server". I googled this message to try and figure out what was causing it and it aprears to be related to gamespy servers across many games, not just Arma. However there is not a single solution I can find to this.
I think this problem may be related to Gamespy, are there any suggestions for sorting this problem out? Can someone please post all ports that Arma 3 uses so that I can confirm that I have them all forward?