Article ID: 249315 - Last Review: November 21, 2006 - Revision: 3.1

BUG: WTSWaitSystemEvent Returns Terminal Services Event Twice

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This article was previously published under Q249315

SYMPTOMS

When using WTSWaitSystemEvent in a tight loop, events are reported twice for each actual event.

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RESOLUTION

The application should expect the event twice, and filter out the second occurrence.

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STATUS

Microsoft has confirmed that this is a bug in the Microsoft products that are listed at the beginning of this article.

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MORE INFORMATION

Steps to Reproduce Behavior

Compile a program that executes the following code:

    DWORD dwEvent;

    while (1){
        if (!WTSWaitSystemEvent(WTS_CURRENT_SERVER_HANDLE, WTS_EVENT_ALL, &dwEvent))
        {
            printf("WTSWaitSystemEvent failed with %u\n", GetLastError());
            break;
        }

        if (dwEvent & WTS_EVENT_CONNECT)
            printf("WTS_EVENT_CONNECT ");

        if (dwEvent & WTS_EVENT_CREATE)
            printf("WTS_EVENT_CREATE ");

        if (dwEvent & WTS_EVENT_DELETE)
            printf("WTS_EVENT_DELETE ");

        if (dwEvent & WTS_EVENT_DISCONNECT)
            printf("WTS_EVENT_DISCONNECT ");

        if (dwEvent & WTS_EVENT_LOGOFF)
            printf("WTS_EVENT_LOGOFF ");

        if (dwEvent & WTS_EVENT_LOGON)
            printf("WTS_EVENT_LOGON ");

        if (dwEvent & WTS_EVENT_RENAME)
            printf("WTS_EVENT_RENAME ");

        if (dwEvent & WTS_EVENT_STATECHANGE)
            printf("WTS_EVENT_STATECHANGE ");

        printf("\n");
    }

If you run the code on a terminal server computer, events are reported twice. For example, if a new session is started, WTS_EVENT_CREATE is reported twice, then WTS_EVENT_LOGON occurs twice, and so on.

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