FSocket GetConnectionState always returns true

When my client disconnects from the server, Unreal never seems to recognize that the disconnect happened in Windows (I have not tried in Linux). It seems like the following conditional should return false when a client disconnects, but this function never returns anything other than SCS_Connected.

 ClientSocket->GetConnectionState() == ESocketConnectionState::SCS_Connected

Cobbling together what few examples I can find on FSocket, this is my code below. It successfully detects the client, and receives data, but cannot detect a client disconnect.

Setting up the server socket:

       Socket = TSharedPtr<FSocket, ESPMode::ThreadSafe>(ISocketSubsystem::Get(PLATFORM_SOCKETSUBSYSTEM)->CreateSocket(NAME_Stream, TEXT("SimulatorSocket"), false));

	FIPv4Address ip;
	FIPv4Address::Parse(address, ip);

	TSharedRef<FInternetAddr> addr = ISocketSubsystem::Get(PLATFORM_SOCKETSUBSYSTEM)->CreateInternetAddr();


Listening loop:

   TArray<uint8> ReceivedData;
	int32 byteCount = 0;
	uint32 Size = 0;
	bool pending = false;

	while (Server->IsRunning()){
		while (Server->IsRunning() && Server->Socket->HasPendingConnection(pending) && pending) {
			UE_LOG(LogTemp, Warning, TEXT("Client detected"));

			TSharedRef<FInternetAddr> RemoteAddress = ISocketSubsystem::Get(PLATFORM_SOCKETSUBSYSTEM)->CreateInternetAddr();
			TSharedPtr<FSocket> ClientSocket = TSharedPtr<FSocket>(Server->Socket->Accept(*RemoteAddress, TEXT("HolodeckServerClient")));

			while (Server->IsRunning() && ClientSocket.IsValid() && ClientSocket->GetConnectionState() == ESocketConnectionState::SCS_Connected) {
				if (ClientSocket->HasPendingData(Size)) {
					ReceivedData.SetNumUninitialized(Size); //FMath::Min(Size, 65507u)
					if (ClientSocket->Recv(ReceivedData.GetData(), ReceivedData.Num(), byteCount)) {
						UE_LOG(LogTemp, Warning, TEXT("Success!"));

						// TODO: Parse the data, create a message, publish
						// Server->Publish(new FHolodeckCommand(.5));

					else {
						// Error receiving data, closing the client socket as a precaution

			if (ClientSocket.IsValid()) {
				UE_LOG(LogTemp, Warning, TEXT("Disconnected from client!"));
				UE_LOG(LogTemp, Warning, TEXT("Closed Socket!"));


Hallo rpotttorff.
Any success on that issue? Im facing the same problem here.

nope - I’m pretty sure it’s an issue/bug… I ended up migrating to ZMQ.

Hi, I have same issue.
plz let me know if you found solution.

The bad news is that it is in fact a bug and Epic has given up in trying to solve it. Here is the stagnant public tracker: Unreal Engine Issues and Bug Tracker (UE-27542)

The good news is that other people have written fixes for it. Here is the pull request:

Good luck!