Keep your friends close and your enemies dead with holy water and a wooden stake
The social part of playing games. Many of these features are now part of platforms such as steam or current generation consoles. One still need hook up the support for them in the game.
A friend system allows the player to add other players as friends. Two useful features to add with a friend system is invite friend and join friend.
Invite Friend: This lets you send a invite to the multiplayer game you are playing. If your friend accept his game will automaticlly connect to the game you are in.
Join Friend: If a friend is playing a multiplayer game you can select this to join the game he is in.
With this it is possible to form a party or group while playing and the matchmaking system will try to keep you in the same game and in the same team.