每臺計算機的應用程序的一個實例，如何？

Question

我試圖讓我的應用程序只運行一次在電腦上，我的應用程序需要comunicate到WebService所以它是壞讓它運行多次，使用互斥這個目前即時通訊：

MyMsg := RegisterWindowMessage('My_Unique_App_Message_Name'); 
Mutex := CreateMutex(nil, True, 'My_Unique_Application_Mutex_Name'); 
if (Mutex = 0) OR (GetLastError = ERROR_ALREADY_EXISTS) then 
exit; 

目前這可以限制每個用戶1個應用程序的實例，但是我的應用程序正在Windows Server環境中使用，其中一次有20多個用戶在使用，所以我需要嚴格限制每個服務器只運行一次，我試圖做的是將Mutex聲明爲全局互斥體，但是當我執行下一個代碼時，它無法工作。

MyMsg := RegisterWindowMessage('My_Unique_App_Message_Name'); 
Mutex := CreateMutex(nil, True, 'Global\My_Unique_Application_Mutex_Name'); 
if (Mutex = 0) OR (GetLastError = ERROR_ALREADY_EXISTS) then 
begin 
exit 

所以我做錯了什麼？有沒有其他可靠的方式不讓我的應用程序的第二個實例運行？

Answer 1

默認情況下，lpMutexAttributes = nil創建的互斥鎖只能由運行該進程的用戶訪問。所有用戶都需要訪問互斥鎖。

空DACL安全描述符

通過使用安全描述符具有空DACL執行此操作。請在下面找到我用於單實例應用程序/服務的代碼

//Creates a mutex to see if the program is already running. 
function IsSingleInstance(MutexName : string; KeepMutex : boolean = true):boolean; 
const MUTEX_GLOBAL = 'Global\'; //Prefix to explicitly create the object in the global or session namespace. I.e. both client app (local user) and service (system account) 

var MutexHandel : THandle; 
    SecurityDesc: TSecurityDescriptor; 
    SecurityAttr: TSecurityAttributes; 
    ErrCode : integer; 
begin 
    // By default (lpMutexAttributes =nil) created mutexes are accessible only by 
    // the user running the process. We need our mutexes to be accessible to all 
    // users, so that the mutex detection can work across user sessions. 
    // I.e. both the current user account and the System (Service) account. 
    // To do this we use a security descriptor with a null DACL. 
    InitializeSecurityDescriptor(@SecurityDesc, SECURITY_DESCRIPTOR_REVISION); 
    SetSecurityDescriptorDacl(@SecurityDesc, True, nil, False); 
    SecurityAttr.nLength:=SizeOf(SecurityAttr); 
    SecurityAttr.lpSecurityDescriptor:=@SecurityDesc; 
    SecurityAttr.bInheritHandle:=False; 

    // The mutex is created in the global name space which makes it possible to 
    // access across user sessions. 
    MutexHandel := CreateMutex(@SecurityAttr, True, PChar(MUTEX_GLOBAL + MutexName)); 
    ErrCode := GetLastError; 

    // If the function fails, the return value is 0 
    // If the mutex is a named mutex and the object existed before this function 
    // call, the return value is a handle to the existing object, GetLastError 
    // returns ERROR_ALREADY_EXISTS. 
    if {(MutexHandel = 0) or }(ErrCode = ERROR_ALREADY_EXISTS) then 
    begin 
    result := false; 
    closeHandle(MutexHandel); 
    end 
    else 
    begin 
    // Mutex object has not yet been created, meaning that no previous 
    // instance has been created. 
    result := true; 

    if not KeepMutex then 
     CloseHandle(MutexHandel); 
    end; 

    // The Mutexhandle is not closed because we want it to exist during the 
    // lifetime of the application. The system closes the handle automatically 
    //when the process terminates. 
end;