UE5多人游戏：通过FSessionSettings传递服务器名称编译报错求助

一、编译错误的核心原因 #

• 直接给FOnlineSessionSetting.Data赋值时未指定数据类型和广告属性，Unreal的在线会话设置需要明确这些参数才能完成序列化/反序列化
• const FName NullName = "NULL";初始化方式不规范，Unreal中FName需用TEXT()宏包裹字符串
• 获取会话设置时未处理FindRef可能返回空值的情况，存在潜在崩溃风险

二、修正后的会话设置代码 #

void UMultiplayerSessionSubsystem::ConfigureSessionSettings(UMultiplayerDataAsset* DataAsset)
{
    IOnlineSubsystem* OnlineSubsystem = IOnlineSubsystem::Get();
    if (!OnlineSubsystem)
    {
        UE_LOG(LogTemp, Error, TEXT("Online Subsystem is null!"));
        return;
    }

    const FName SubsystemName = OnlineSubsystem->GetSubsystemName();
    const FName NullName = FName(TEXT("NULL"));

    SessionSettings = MakeShareable(new FOnlineSessionSettings());
    SessionSettings->NumPublicConnections = DataAsset->MaxPlayersCount;
    SessionSettings->NumPrivateConnections = DataAsset->MaxPlayersCount;
    SessionSettings->bIsLANMatch = SubsystemName == NullName;
    SessionSettings->bIsDedicated = false;
    SessionSettings->bAllowJoinInProgress = true;
    SessionSettings->bAllowJoinViaPresence = true;
    SessionSettings->bUseLobbiesIfAvailable = true;
    SessionSettings->bShouldAdvertise = true;
    SessionSettings->bUsesPresence = true;
    SessionSettings->bAllowInvites = true;

    // 正确初始化会话名称设置：指定数据类型、广告属性、赋值
    FOnlineSessionSetting SessionNameSetting;
    SessionNameSetting.Data = DataAsset->OwnerPlayerName;
    SessionNameSetting.AdvertisementType = EOnlineDataAdvertisementType::ViaOnlineServiceAndPing;
    SessionNameSetting.SetDataType(FString::StaticStruct());
    SessionSettings->Settings.Add(FName(TEXT("SESSION_NAME")), SessionNameSetting);

    SessionSettings->Set(FName(TEXT("MatchType")), DataAsset->GameTypeName.ToString(), EOnlineDataAdvertisementType::ViaOnlineServiceAndPing);
}

三、安全获取服务器名称的代码 #

// 遍历搜索结果时的安全获取逻辑
for (int32 i = 0; i < LastSessionSearch->SearchResults.Num(); ++i)
{
    const FOnlineSessionSearchResult& Result = LastSessionSearch->SearchResults[i];
    FString SessionName = TEXT("Unnamed Server");

    // 先检查设置是否存在，避免空引用
    const FName SessionNameKey = FName(TEXT("SESSION_NAME"));
    if (Result.Session.SessionSettings.Settings.Contains(SessionNameKey))
    {
        const FOnlineSessionSetting& Setting = Result.Session.SessionSettings.Settings[SessionNameKey];
        // 验证数据有效性和类型匹配
        if (Setting.Data.IsValid() && Setting.Data.GetType() == FString::StaticStruct())
        {
            SessionName = *Setting.Data.GetValue<FString>();
        }
    }

    UE_LOG(LogTemp, Warning, TEXT("SERVER NAME: %s"), *SessionName);
    // 此处可将SessionName绑定到UI控件，实现会话列表显示
}

四、关键注意事项 #

• 确保DataAsset->OwnerPlayerName是有效的FString类型，避免空字符串
• 在线子系统（如Steam、EOS）需正确配置，否则会话设置无法跨客户端同步
• 测试优先用LAN模式（Null子系统）验证功能，再切换到正式在线服务

内容的提问来源于stack exchange，提问作者Infinix Gaming