CreateMutex实现只能打开一个客户端

#include "stdafx.h"
#include <Windows.h>
#include <iostream>

using namespace std;

int _tmain (int argc, LPTSTR argv[])
{
    HANDLE h=CreateMutex(NULL,TRUE,"AAAAAAA");
    if(GetLastError()==ERROR_ALREADY_EXISTS){
        CloseHandle(h);
        return ;
    }
    system("pause");
    CloseHandle(h);
    return ;
}