To make a multiplayer game, you first need a game server. There, you already have 2 alternatives: 1. Host your own Custom server 2. Use an external service like playfab or player.io. If you use something like player.io, you need to learn a specific programming language ( in this case C# ). If you make your custom server, you can use pretty much any language. In any case, you will need some basic programming knowledge and for gdevelop at least a bit of javascript.
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