Network Level Manager

The plNetworkLevelManager handles synchronized level loading across the server and all clients. It ensures all machines have loaded the same level before gameplay begins, with timeout handling and late-joiner support.

Overview

When the server decides to load a level, all clients must load it before gameplay can start. The Level Manager coordinates this:

Server sends a LevelLoad message with the level path.
Each client loads the level and sends a LevelLoadComplete acknowledgment.
When all clients have acknowledged (or the timeout expires), the server sends LevelStart.
All machines begin gameplay simultaneously.

Accessing the Manager

plNetworkLevelManager* pLevelMgr = pNetModule->GetLevelManager();

Level States

State	Description
`None`	No level load in progress
`Loading`	Level load requested, waiting for client acknowledgments
`Ready`	All clients loaded (or timed out), level is playable

Server API

Request Level Load

pLevelMgr->RequestLevelLoad(
  "Levels/Mission01.plScene",  // Level asset path
  30.0f);                       // Timeout in seconds (0 = no timeout)

This sends a LevelLoad message to all connected clients and transitions to the Loading state.

Check Loading Status

plNetworkLevelState::Enum state = pLevelMgr->GetState();
const plString& levelPath = pLevelMgr->GetCurrentLevelPath();
bool bAllLoaded = pLevelMgr->AreAllClientsLoaded();

Late-Joiner Sync

When a new client connects during or after a level load, sync the current level:

pLevelMgr->SyncLevelToClient(newClientID);

This is called automatically by the plNetworkWorldModule during the handshake process. The client receives the LevelLoad message, loads the level, sends its ack, and then receives LevelStart individually.

Client API

Handle Level Load

When a LevelLoad message arrives, the Level Manager broadcasts a plMsgNetworkLevelLoadRequested to all network components. Override the handler in your component to load the level and then notify completion:

void MyGameComponent::OnNetworkLevelLoadRequested(plMsgNetworkLevelLoadRequested& ref_msg) override
{
  // Load the level (async or sync)
  LoadLevel(ref_msg.m_sLevelPath);

  // When done, notify the server
  m_pNetworkModule->GetLevelManager()->NotifyLoadComplete();
}

Handle Level Start

When the server signals all clients are loaded, a plMsgNetworkLevelStart is broadcast:

void MyGameComponent::OnNetworkLevelStart(plMsgNetworkLevelStart& ref_msg) override
{
  // All clients loaded -- begin gameplay
  StartGameplay();
}

Timeout

If a client fails to acknowledge within the timeout period, the server proceeds with LevelStart anyway. This prevents a single slow or disconnected client from blocking everyone.

The timeout is specified per load request:

pLevelMgr->RequestLevelLoad("Levels/Mission01.plScene", 30.0f);

A timeout of 0.0f disables the timeout (wait forever).

Messages

All level events are delivered as plMessage types to plNetworkComponent subclasses:

Message	Side	When Sent
`plMsgNetworkLevelLoadRequested`	Client / Host	Server requests a level load
`plMsgNetworkLevelStart`	All	Server signals gameplay can begin
`plMsgNetworkAllClientsLoaded`	Server	All clients finished loading (before LevelStart)

void MyGameComponent::OnNetworkAllClientsLoaded(plMsgNetworkAllClientsLoaded& ref_msg) override
{
  plLog::Info("All clients loaded! Starting gameplay...");
}

Server-Side Flow

Integration with Session

The Network Session integrates with the Level Manager automatically. When you call pSession->StartGame("Mission01"), it internally calls RequestLevelLoad() on the Level Manager and manages the state transitions.

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