C++ overview

Add ServerQueueCore to your module's dependencies:

PublicDependencyModuleNames.AddRange(new string[] { "ServerQueueCore" });

The queue core

FServerQueueCore (Core/ServerQueueCore.h) holds all queue logic, with no networking and no engine clock. Every call takes the current time, so it can be driven and tested directly.

• UServerQueueSubsystem::GetCore() returns the server's instance.
• OnQueueEvent reports slot grants, expiries and queue changes.
• Parties go through RequestJoinParty and JoinParty.
• UServerQueueSubsystem::RequestJoinAsync takes an FServerQueueJoinRequest with the party member keys or the leader key.

Your own game session

If you can't use ServerQueueGameSession, call the queue from your own game session class:

#include "Server/ServerQueueSubsystem.h"

FString AMyGameSession::ApproveLogin(const FString& Options)
{
	const FString ErrorMessage = Super::ApproveLogin(Options);
	UServerQueueSubsystem* Queue = UGameInstance::GetSubsystem<UServerQueueSubsystem>(GetGameInstance());
	if (ErrorMessage.IsEmpty() && Queue && Queue->IsActive())
	{
		Queue->CaptureLoginOptions(Options);
	}
	return ErrorMessage;
}

bool AMyGameSession::AtCapacity(bool bSpectator)
{
	// The queue tracks slots, including reservations the engine does not know about.
	UServerQueueSubsystem* Queue = UGameInstance::GetSubsystem<UServerQueueSubsystem>(GetGameInstance());
	if (Queue && Queue->IsActive())
	{
		return false;
	}
	return Super::AtCapacity(bSpectator);
}

A ticket per connection

UServerQueueClientSubsystem::OnMakeAuthTicket() makes the ticket for each connection to a queue, reconnects included, for tickets that work only once. It wins over Set Auth Ticket; return an empty string to fall back to it.

UServerQueueClientSubsystem* Queue = GetGameInstance()->GetSubsystem<UServerQueueClientSubsystem>();
Queue->OnMakeAuthTicket().BindUObject(this, &UMyTicketSubsystem::MakeTicket);

Server Queue Steam uses this for Steam session tickets. See Steam.