Monster Hunter Tri official servers are down, but (like Minty Fresh / MH3 Server Project ) exist:
Monster Hunter Tri's multiplayer mode allows up to four players to join forces and tackle challenging quests together. Players can join or create online sessions, using the Nintendo Wii's online features to connect with friends and fellow hunters. The game's multiplayer mode adds a new layer of depth and replayability, as players work together to take down massive monsters and complete difficult quests. Monster Hunter Tri -RMHE08- WBFS