There are three main common solutions for the online mode of Arma 3. Specific details include: using your own host as a server, using online patches and joining a third-party battle platform. You only need to add the same IP address to connect.
The first way is to rent a server
Players can use their own host as a server, then create a room and wait for other players to join.
The second way is to use online patching
By installing the same patch, players can play online more conveniently. Only players with the same patch installed can connect online.
The last way is to use a third-party battle platform for online games
This method does not require players to load the same MOD, only the same IP address.
Game Strategy: Beginner Tutorial Strategy