AGameModeBase::PreLoginAsync

function Engine Since 4.24

#include "GameFramework/GameModeBase.h"

Access: public Specifiers: virtual

Description

Async version of `PreLogin` that allows off-thread backend calls (e.g. ban checks or entitlement verification) before accepting a connection. Must call `OnComplete` when finished.

Caveats & Gotchas

• **You must call `OnComplete` exactly once**, even on failure or timeout. Failing to do so causes the connecting client to hang indefinitely waiting for a response, eventually timing out.
• The base implementation calls synchronous `PreLogin` and immediately fires `OnComplete` — you only need to override this if you require a genuinely async operation. Do not override both `PreLogin` and `PreLoginAsync` unless you call `PreLogin` from your `PreLoginAsync` override.
• If your async work can fail (e.g. the backend is unreachable), decide on a fail-open or fail-closed policy explicitly. The engine has no default timeout for the async case.

Signature

virtual void PreLoginAsync(const FString& Options, const FString& Address, const FUniqueNetIdRepl& UniqueId, const FOnPreLoginCompleteDelegate& OnComplete)

Parameters

Name	Type	Description	Default
Options	const FString&	The URL options string from the connecting client.	—
Address	const FString&	The network address of the connecting player.	—
UniqueId	const FUniqueNetIdRepl&	The platform-specific unique ID of the connecting player.	—
OnComplete	const FOnPreLoginCompleteDelegate&	Delegate that MUST be called with the error message (empty = success) when the async check finishes.	—

Return Type

void

Example

Async ban check against a backend service C++

void AMyGameMode::PreLoginAsync(const FString& Options, const FString& Address,
    const FUniqueNetIdRepl& UniqueId, const FOnPreLoginCompleteDelegate& OnComplete)
{
    // Kick off async HTTP ban check
    TSharedRef<IHttpRequest> Req = FHttpModule::Get().CreateRequest();
    Req->SetURL(FString::Printf(TEXT("https://api.mygame.com/bans/%s"), *UniqueId.ToString()));
    Req->SetVerb(TEXT("GET"));
    Req->OnProcessRequestComplete().BindLambda(
        [OnComplete](FHttpRequestPtr, FHttpResponsePtr Response, bool bSuccess)
        {
            FString Error;
            if (!bSuccess || !Response.IsValid())
            {
                // Fail-open: allow on backend error
            }
            else if (Response->GetContentAsString().Contains(TEXT("banned")))
            {
                Error = TEXT("You are banned from this server.");
            }
            OnComplete.ExecuteIfBound(Error);
        });
    Req->ProcessRequest();
}

Version History

Introduced in: 4.24

Version	Status	Notes
5.6	stable	—

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