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Unreal SDK failing to handle fragmented messages #4002

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Merged
JasonAtClockwork merged 3 commits into from
Jan 13, 2026
Merged

Unreal SDK failing to handle fragmented messages #4002

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86ce20d
Turns out Unreal's OnRawMessage never seems to return BytesRemaining,…
JasonAtClockwork Jan 12, 2026
38e5a73
Merge branch 'master' into jlarabie/fix-unreal-fragments
JasonAtClockwork Jan 12, 2026
8a743c8
Merge branch 'master' into jlarabie/fix-unreal-fragments
JasonAtClockwork Jan 12, 2026
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37 changes: 16 additions & 21 deletions sdks/unreal/src/SpacetimeDbSdk/Source/SpacetimeDbSdk/Private/Connection/Websocket.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -81,7 +81,7 @@ void UWebsocketManager::Connect(const FString& ServerUrl)
WebSocket->OnConnected().AddUObject(this, &UWebsocketManager::HandleConnected);
WebSocket->OnConnectionError().AddUObject(this, &UWebsocketManager::HandleConnectionError);
WebSocket->OnMessage().AddUObject(this, &UWebsocketManager::HandleMessageReceived);
WebSocket->OnRawMessage().AddUObject(this, &UWebsocketManager::HandleBinaryMessageReceived);
WebSocket->OnBinaryMessage().AddUObject(this, &UWebsocketManager::HandleBinaryMessageReceived);
WebSocket->OnClosed().AddUObject(this, &UWebsocketManager::HandleClosed);

UE_LOG(LogTemp, Log, TEXT("UWebsocketManager::Connect: Connecting to %s..."), *ServerUrl);
Expand Down Expand Up @@ -173,7 +173,7 @@ void UWebsocketManager::HandleMessageReceived(const FString& Message)
OnMessageReceived.Broadcast(Message);
}

void UWebsocketManager::HandleBinaryMessageReceived(const void* Data, SIZE_T Size, SIZE_T BytesRemaining)
void UWebsocketManager::HandleBinaryMessageReceived(const void* Data, SIZE_T Size, bool bIsLastFragment)
{
if (Size == 0)
{
Expand All @@ -183,30 +183,25 @@ void UWebsocketManager::HandleBinaryMessageReceived(const void* Data, SIZE_T Siz
// Handle binary messages, which may be fragmented
const uint8* Bytes = static_cast<const uint8*>(Data);

if (IncompleteMessage.Num() > 0 && !bAwaitingBinaryFragments)
{
UE_LOG(LogTemp, Error, TEXT("Received binary fragment while previous data pending"));
}

// Append new incoming bytes to any incomplete message
// Append this fragment to our buffer
IncompleteMessage.Append(Bytes, Size);

if (BytesRemaining > 0)
// If this is the last fragment, we have the complete message
if (bIsLastFragment)
{
// We have the complete message
TArray<uint8> MessageBytes = IncompleteMessage;
IncompleteMessage.Reset();
bAwaitingBinaryFragments = false;

// Forward the complete binary payload to listeners.
OnBinaryMessageReceived.Broadcast(MessageBytes);
}
else
{
// Still expecting more fragments
// More fragments are coming
bAwaitingBinaryFragments = true;
return;
}

// Final fragment received, reset and process
bAwaitingBinaryFragments = false;

TArray<uint8> MessageBytes = IncompleteMessage;
IncompleteMessage.Reset();

// Forward the complete binary payload to listeners.
OnBinaryMessageReceived.Broadcast(MessageBytes);

}

void UWebsocketManager::HandleClosed(int32 StatusCode, const FString& Reason, bool bWasClean)
Expand Down
2 changes: 1 addition & 1 deletion sdks/unreal/src/SpacetimeDbSdk/Source/SpacetimeDbSdk/Public/Connection/Websocket.h
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Original file line number Diff line number Diff line change
Expand Up @@ -106,7 +106,7 @@ class SPACETIMEDBSDK_API UWebsocketManager : public UObject
/** Handler for incoming text messages */
void HandleMessageReceived(const FString& Message);
/** Handler for incoming binary messages */
void HandleBinaryMessageReceived(const void* Data, SIZE_T Size, SIZE_T BytesRemaining);
void HandleBinaryMessageReceived(const void* Data, SIZE_T Size, bool bIsLastFragment);
/** Handler for socket close */
void HandleClosed(int32 StatusCode, const FString& Reason, bool bWasClean);

Expand Down
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