delphi - 每台计算机一个应用程序实例，怎么样？

Question

我试图让我的应用程序在计算机上仅运行一次，我的应用程序需要与网络服务通信，因此让它运行多次是不好的，目前我使用互斥体:

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，这可以限制每个用户 1 个应用程序实例，但我的应用程序正在 Windows Server 环境中使用，其中一次有 20 多个用户登录，因此我需要将其严格限制为每个服务器仅运行一次，我想做的是将互斥体声明为全局互斥体，但当我执行下一个代码时我没有这样做，它根本不起作用。

 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

所以我做错了什么吗？有没有其他可靠的方法来不让我的应用程序的第二个实例运行？

Answer 1

默认情况下，lpMutexAttributes = nil 创建的互斥体只能由运行该进程的用户访问。互斥体需要可供所有用户访问。

空 DACL 安全描述符

通过使用具有空 DACL 的安全描述符来执行此操作。请在下面找到我用于单实例应用程序/服务的代码

//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;