====== マルチプレイのセットアップ ======
<note important>検証中</note>

===== 要件 =====
  * [[https://dev.epicgames.com/documentation/ja-jp/unreal-engine/online-subsystem-in-unreal-engine|Online Subsystem]]
  * [[https://dev.epicgames.com/documentation/ja-jp/unreal-engine/online-subsystem-steam-interface-in-unreal-engine?application_version=5.5|Online Subsystem Steam]]
  * [[https://dev.epicgames.com/documentation/ja-jp/unreal-engine/using-steam-sockets-in-unreal-engine|Steam Socket]]

  * Steamをターゲットとし、EOSは使わない
  * リッスンサーバー
  * UE5.5

<code ini>
[/Script/Engine.GameEngine]
!NetDriverDefinitions=ClearArray
+NetDriverDefinitions=(DefName="GameNetDriver",DriverClassName="/Script/SteamSockets.SteamSocketsNetDriver",DriverClassNameFallback="/Script/SteamSockets.SteamNetSocketsNetDriver")
; 公式Doc通りだと以下
; [/Script/Engine.GameEngine]
; +NetDriverDefinitions=(DefName="GameNetDriver",DriverClassName="OnlineSubsystemSteam.SteamNetDriver",DriverClassNameFallback="OnlineSubsystemUtils.IpNetDriver")
	 
[OnlineSubsystem]
DefaultPlatformService=Steam

[OnlineSubsystemSteam]
bEnabled=true
SteamDevAppId=480
SteamAppId=480
; GameServerQueryPort=27015
bInitServerOnClient=true
bUsesPresence=true
bUseLobbiesIfAvailable=true
bUseSteamNetworking=true
bAllowP2PPacketRelay=true

[/Script/OnlineSubsystemSteam.SteamNetDriver]
NetConnectionClassName="OnlineSubsystemSteam.SteamNetConnection";
</code>

===== バグ対処 =====
DefaultEngine.ini で bUseLobbiesIfAvailable=true と設定しても、false となる。\\
JoinSession時に、bUsesPresence と FOnlineSessionSettings::bUseLobbiesIfAvailable
<code ini>
[FOnlineSessionSteam::JoinSession] The values of FOnlineSessionSettings::bUsesPresence and FOnlineSessionSettings::bUseLobbiesIfAvailable are treated as equal and have to match
</code>

<code c++>
    UFUNCTION(BlueprintCallable, Category = "VshsSteam|Session")
    static void FixSteamSearchResultFlags(UPARAM(ref) FBlueprintSessionResult& SessionResult);
</code>
<code c++>
void UVshsSteamFunctions::FixSteamSearchResultFlags(FBlueprintSessionResult& SessionResult)
{
    FOnlineSessionSearchResult& NativeResult = SessionResult.OnlineResult;
    NativeResult.Session.SessionSettings.bUsesPresence = true;
    NativeResult.Session.SessionSettings.bUseLobbiesIfAvailable = true;
}
</code>


===== おバカ事例 =====
  * Standalone Game で実行して Steamオーバーレイが出るが、セッションを作成できない
    * Play As Listen Server でプレイしていないか？おそらくSteamNetDriver が 同じP2Pポートで2重Listenを試みて失敗