Unity Netcode overview - Step-by-Step Execution

Concept Flow - Unity Netcode overview

Start: Game Launch

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Initialize Network Manager

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Choose Role: Host / Client

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Host: Start Server

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Synchronize Game State

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Send/Receive Network Messages

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Update Game Objects Across Network

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Gameplay

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End or Disconnect

This flow shows how Unity Netcode starts with initializing the network, choosing host or client roles, connecting, syncing game state, and updating objects during gameplay.

Execution Sample

Unity

NetworkManager.Singleton.StartHost();
// Host starts server and client

NetworkManager.Singleton.StartClient();
// Client connects to server

// Networked objects sync automatically

This code starts a host or client in Unity Netcode, enabling networked gameplay with automatic synchronization.

Execution Table

Step	Action	NetworkManager State	Result
1	Call StartHost()	IsHost = false, IsClient = false	Starts server and client, IsHost = true, IsClient = true
2	Host waits for clients	IsHost = true, IsClient = true	Server ready, waiting for clients to connect
3	Call StartClient() on client	IsHost = false, IsClient = false	Client connects to server, IsClient = true
4	Server and client synchronize	IsHost = true, IsClient = true (host), IsClient = true (client)	Game state synced across network
5	Networked objects update	Objects have NetworkObject component	Objects' states replicate on all clients
6	Gameplay continues	NetworkManager running	Players interact with synced game world
7	Disconnect or stop	NetworkManager active	Network session ends, cleanup happens

💡 Execution stops when the network session ends or game closes.

Variable Tracker

Variable	Start	After Step 1	After Step 3	After Step 4	Final
IsHost	false	true	false	false	false (after disconnect)
IsClient	false	true	true	true	false (after disconnect)
Network Objects Synced	No	No	No	Yes	No (after disconnect)

Key Moments - 3 Insights

Why does the host have both IsHost and IsClient true?

Because the host runs both server and client in one instance, as shown in execution_table step 1.

How do networked objects update on all players?

Objects with NetworkObject component automatically sync their state across clients, as in step 5.

What happens if a client disconnects?

The network session cleans up and stops syncing for that client, shown in the exit_note and final variable states.

Visual Quiz - 3 Questions

Look at the execution_table, what is the NetworkManager state after calling StartHost()?

A IsHost = false, IsClient = true

B IsHost = true, IsClient = true

C IsHost = true, IsClient = false

D IsHost = false, IsClient = false

💡 Hint

Check execution_table row 1 under NetworkManager State.

At which step do networked objects start syncing their state?

A Step 5

B Step 4

C Step 3

D Step 6

💡 Hint

Look at execution_table row 5 describing object updates.

If the client never calls StartClient(), what happens to IsClient variable in variable_tracker?

A It toggles between true and false

B It becomes true anyway

C It stays false

D It causes an error

💡 Hint

Refer to variable_tracker row for IsClient and step 3 in execution_table.

Concept Snapshot

Unity Netcode overview:
- Use NetworkManager to start Host or Client
- Host runs server and client together
- Clients connect to Host server
- NetworkObjects sync state automatically
- NetworkManager manages connection lifecycle
- Gameplay updates sync across network

Full Transcript

Unity Netcode starts by initializing the NetworkManager. The game chooses a role: host or client. The host starts both server and client, setting IsHost and IsClient to true. Clients connect to the host by calling StartClient, setting IsClient to true. The server and clients synchronize game state automatically through NetworkObjects. During gameplay, all networked objects update their state across all players. When the session ends or a player disconnects, the network cleans up and stops syncing. This flow ensures smooth multiplayer gameplay with automatic state synchronization.