Why multiplayer requires networking in Unity

Introduction

Multiplayer games need networking to let players connect and play together from different places. Networking sends game data between players so everyone sees the same game world.

When you want friends to play a game together online.

When players are on different devices and need to share game actions.

When you want to keep all players’ game views in sync.

When you want to create a shared game world that updates for everyone.

When you want to allow players to chat or trade items in real time.

Syntax

Unity

using UnityEngine;
using Unity.Netcode;

public class SimpleNetwork : NetworkBehaviour {
    public override void OnNetworkSpawn() {
        if (IsServer) {
            Debug.Log("Server started");
        }
        if (IsClient) {
            Debug.Log("Client connected");
        }
    }
}

Unity uses the Unity.Netcode library to handle networking.

NetworkBehaviour is a special class for networked objects.

Examples

This code moves the player only if it is the owner of the object, so each player controls their own character.

Unity

public class PlayerMovement : NetworkBehaviour {
    void Update() {
        if (!IsOwner) return;
        float move = Input.GetAxis("Horizontal");
        transform.Translate(move * Time.deltaTime, 0, 0);
    }
}

This shows how a client can send a message to the server using a ServerRpc method.

Unity

public class ChatMessage : NetworkBehaviour {
    [ServerRpc]
    public void SendMessageServerRpc(string message) {
        Debug.Log($"Message from client: {message}");
    }
}

Sample Program

This simple Unity script shows a networked player object. The server logs when it starts, clients log when they connect, and each player can move their own character left or right.

Unity

using UnityEngine;
using Unity.Netcode;

public class SimpleMultiplayer : NetworkBehaviour {
    public override void OnNetworkSpawn() {
        if (IsServer) {
            Debug.Log("Server is running");
        }
        if (IsClient) {
            Debug.Log("Client connected");
        }
    }

    void Update() {
        if (!IsOwner) return;
        float move = Input.GetAxis("Horizontal");
        transform.Translate(move * Time.deltaTime, 0, 0);
    }
}

Important Notes

Networking is needed to share game state between players in real time.

Each player controls only their own character to avoid conflicts.

Unity's Netcode library simplifies sending data between server and clients.

Summary

Multiplayer games need networking to connect players and share game data.

Networking keeps all players’ game views synchronized.

Unity provides tools to help build multiplayer games easily.