Client Server Model UE5

The main things that multiplayer is all about is Input and State.

• State is everything in the world, velocity, positions, etc…
• In the state we add inputs which is telling the player to move or perform an action.
• During the tick you combine the current state with the current actions and the result is the 2nd state.
• This leads to what the player sees in happening in the game
• Rinse and Repeat

For multiplayer the players state must be updating together.

• One way to do this is Peer-to-Peer
• If you make a change to the input from one system you make a state change to every player. You must listen to everyone elses input before you do the next Tick as well.
• Peer-to-Peer is one of the least reliable methods for multiplayer
• A more reliable version is to go with the Client-Server model.
• Where a computer recieves input from the other devices and send the state updates to the clients.

Let’s try to do this ourselves. Open up a command prompt window. The goal is to launch a game from the command line.

• Get the UnrealEditor.Exe from your Unreal Version file normally in your programs folder, and paste it in the command prompt.
• Do the same for the Project you created as well.
• To make sure if launches a game place a -game at the end.

This is great for testing especially if there is a bug that keeps crashing the game.

You can also put -log at the end to get more infomration about what’s happening in the game.

If you want to load a specific map you can pick it by exe gamelocation /GAME/ThirdPersonCPP/Maps/ThirdPersonExampleMap — Game

You could also put in an IP address instead of a map. This is the way to connect to a server. So we will swap out -game for -server

Your server will now launch. You can verify this as the log window will launch as well.

Now we can connect a client.

• Instead of a map we will put in your IP address and server with game.

• If when you launch and are getting a black screen there might be a problem where you aren’t on the correct port. The port might have to be specified.
• On the server log do a ctrl+f and search for listening. This will show what port the server is listening on.

The game will now launch.

• Go back to the command prompt and launch a second instance. Now both will be connected to the server.

Congratulations! First steps of local multiplayer via client-server have been achieved!