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MultiplayerDebugTools

A modern, runtime Unreal Engine plugin that gives you a lightweight multiplayer diagnostics HUD directly in the viewport.

Core controls
  • Toggle key: F10
  • Console command: mdt.Toggle
  • Overlay widget: SMultiplayerDebugOverlay
  • Subsystem: UMultiplayerDebugSubsystem (UGameInstanceSubsystem)
  • Engine support: UE 4.27 → UE 5.7

Why It’s Useful​

Multiplayer debugging can get noisy and slow. MultiplayerDebugTools keeps critical network and gameplay replication signals visible while you iterate:

  • ✅ Fast session health checks in PIE
  • ✅ Visual thresholds for instant “good/warn/bad” feedback
  • ✅ Blueprint + C++ control points for custom workflows
  • ✅ Minimal runtime overhead and simple integration

What You Can See In-Game​

MetricDescription
RoleStandalone, Client, Listen Server, or Dedicated Server
FPSSampled from GAverageFPS
Ping (ms)Average across active net connections
Loss In (%)Inbound packet loss
Loss Out (%)Outbound packet loss
RecvInbound bandwidth (B/s, KB/s, MB/s)
SentOutbound bandwidth (B/s, KB/s, MB/s)
ActorsTotal actor count in world
Net ActorsReplicated actor count (GetIsReplicated())

If no network connection exists, network-dependent metrics are shown as N/A.

Visual Thresholds​

FPS​

  • 🟢 Good: >= 55
  • 🟡 Warning: >= 25 and < 55
  • 🔴 Critical: < 25

Ping​

  • 🟢 Good: < 50 ms
  • 🟡 Warning: < 100 ms
  • 🔴 Critical: >= 100 ms

Packet Loss​

  • 🟢 Good: < 1%
  • 🟡 Warning: < 5%
  • 🔴 Critical: >= 5%

Disabled metrics appear as Off in a dimmed style.

Installation​

  1. Copy MultiplayerDebugTools into your project Plugins/ folder.
  2. Open your project in Unreal Editor.
  3. Enable Multiplayer Debug Tools via Edit → Plugins.
  4. Restart when prompted.

Quick Usage (PIE Multiplayer Check)​

  1. Set Number of Players to 2+.
  2. Choose Listen Server play mode.
  3. Start PIE.
  4. Press F10 in each window and compare values (role, ping, packet loss, bandwidth).

Blueprint API​

Access the subsystem through Game Instance subsystem access.

Main Functions​

  • ToggleOverlay()
  • IsOverlayVisible() -> bool
  • GetStatsSnapshot() -> FMultiplayerDebugStatsSnapshot
  • RefreshStatsNow()
  • SetStatsUpdateInterval(float InSeconds)
  • GetStatsUpdateInterval() -> float
  • GetFeatureToggles() -> FMultiplayerDebugFeatureToggles
  • SetFeatureToggles(FMultiplayerDebugFeatureToggles)
  • SetFeatureEnabled(EMultiplayerDebugMetric Feature, bool bEnabled)
  • IsFeatureEnabled(EMultiplayerDebugMetric Feature) -> bool
  • SetAllFeaturesEnabled(bool bEnabled)

Event Dispatcher​

  • OnStatsUpdated(FMultiplayerDebugStatsSnapshot Snapshot)

EMultiplayerDebugMetric​

  • Role
  • FPS
  • Ping
  • PacketLoss
  • Bandwidth
  • ActorCounts

FMultiplayerDebugStatsSnapshot​

  • EnabledFeatures
  • NetRole
  • FPS
  • PingMs
  • PacketLossInPercent
  • PacketLossOutPercent
  • BandwidthInBytesPerSecond
  • BandwidthOutBytesPerSecond
  • TotalActors
  • ReplicatedActors
  • bHasNetworkConnection

FMultiplayerDebugFeatureToggles​

  • bRole
  • bFPS
  • bPing
  • bPacketLoss
  • bBandwidth
  • bActorCounts

C++ Example​

#include "MultiplayerDebugSubsystem.h"

if (UGameInstance* GI = GetGameInstance())
{
    if (UMultiplayerDebugSubsystem* DebugSub = GI->GetSubsystem<UMultiplayerDebugSubsystem>())
    {
        DebugSub->ToggleOverlay();
        DebugSub->SetFeatureEnabled(EMultiplayerDebugMetric::Bandwidth, true);
        DebugSub->SetStatsUpdateInterval(0.2f);
    }
}

Bind to updates:

DebugSub->OnStatsUpdated.AddDynamic(this, &UMyObject::HandleStatsUpdated);

Runtime Behavior​

  • Stats ticker default: 0.25s (minimum clamp via API: 0.05s)
  • Actor count refresh: 1.0s
  • Overlay refresh timer: 0.25s
  • Data collection source:
    • Client: ServerConnection
    • Server: aggregated ClientConnections
  • Dedicated server (UE_SERVER) skips Slate overlay/input handling

Build Dependencies​

  • Public: Core, CoreUObject, Engine, InputCore
  • Private (non-server): Slate, SlateCore

If your game module includes plugin headers, add "MultiplayerDebugTools" to module dependencies.

Notes & Troubleshooting​

note
  • No viewport means no overlay (expected on dedicated server process).
  • In non-networked sessions, network metrics showing N/A is expected.
  • If F10 does nothing, try mdt.Toggle in console.
  • If ping/loss/bandwidth remains N/A, verify the session is actually networked.