I have been doing some testing with MHFU and found the ports needed to do quests with people. It seems each player you play with has a different port starting from 20001 then it increments by 1 every extra person you have so if you want to play with 3 people besides yourself you need to forward 20001, 20002, 20003 and these ports MUST be forwarded by whoever starts the initial quest. So if any of your friends want to choose the quest they have to forward the above ports so the people getting it from the quest board can connect to the person hosting the quest.