Windows Service程序Howto

参考了windows system programming chapter13的内容，但是一些注意点没讲到。

1. 创建windows console应用程序。vs自带的windows service模板创建出来的项目看不懂。

2. _tmain函数这样写：

/*  Main routine that starts the service control dispatcher */
VOID _tmain (int argc, LPTSTR argv[])
{
    SERVICE_TABLE_ENTRY DispatchTable[] =
    {
        { ServiceName,                ServiceMain    },
        { NULL,                        NULL }
    };

    StartServiceCtrlDispatcher (DispatchTable);
    return;
}

关键就是ServiceMain函数在这里定义了。

3. 然后就是ServiceMain函数： 

/*    ServiceMain entry point, called when the service is created by
    the main program.  */
void WINAPI ServiceMain (DWORD argc, LPTSTR argv[])
{
    HANDLE hFile = NULL;
    DWORD Context = 1;
    size_t bytes_need_write = 0;
    DWORD bytes_written = 0;
    TCHAR write_buffer[255];
    SYSTEMTIME cur_time;
    DWORD n;
    LARGE_INTEGER file_size;

    // init logger
    logger_set_root_directory(TEXT("C:\\"));

    hServStatus.dwServiceType = SERVICE_WIN32_OWN_PROCESS;
    hServStatus.dwCurrentState = SERVICE_START_PENDING;
    hServStatus.dwControlsAccepted = SERVICE_ACCEPT_STOP | SERVICE_ACCEPT_SHUTDOWN;
    hServStatus.dwWin32ExitCode = ERROR_SERVICE_SPECIFIC_ERROR;
    hServStatus.dwServiceSpecificExitCode = 0;
    hServStatus.dwCheckPoint = 0;
    // in 2000ms, we should increment dwCheckPoint or set new status
    // while current status is a PENDING start/continue/stop state
    hServStatus.dwWaitHint = 5000;

    /* Warning. Older VC++ version do not have RegisterServiceCtrlHandlerEx
     * defined. You can use RegisterServiceCtrlHandler just as well */
#ifdef RegisterServiceCtrlHandlerEx
    hSStat = RegisterServiceCtrlHandlerEx(ServiceName, ServerCtrlHandlerEx, &Context);
#else
    hSStat = RegisterServiceCtrlHandler(ServiceName, ServerCtrlHandler);
#endif

    if (hSStat == NULL) {
        GET_ERROR_CODE(n);
        UTILS_RIF_WITH_LOG(FALSE, LOG_LEVEL_ERROR, __SDFILE__, __LINE__, 
            TEXT("Register service ctrl handle failed. Reason: %s\n"), 
            utils_format_error_string(n));
    }

    // PENDING start
    if (!SetServiceStatus (hSStat, &hServStatus)) {
        GET_ERROR_CODE(n);
        UTILS_RIF_WITH_LOG(FALSE, LOG_LEVEL_ERROR, __SDFILE__, __LINE__, 
            TEXT("Set service status failed. Reason: %s\n"), 
            utils_format_error_string(n));
    }

    // Open the file and log current time
    hFile = CreateFile(TEXT("C:\\testserv.txt"), GENERIC_WRITE, FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
    if (hFile == INVALID_HANDLE_VALUE) {
        GET_ERROR_CODE(n);
        UTILS_RIF_WITH_LOG(FALSE, LOG_LEVEL_ERROR, __SDFILE__, __LINE__, 
            TEXT("Create testserv file failed. Reason: %s\n"), 
            utils_format_error_string(n));
    }

    // Seek to the end of file
    UTILS_RETURN_IF_FAIL(GetFileSizeEx(hFile, &file_size));
    UTILS_RETURN_IF_FAIL(SetFilePointerEx(hFile, file_size, NULL, FILE_BEGIN));

    GetLocalTime(&cur_time);
    StringCchPrintf(write_buffer, _countof(write_buffer), TEXT("TestServ started, write time: %d-%d-%d %d:%d:%d\n"), 
        cur_time.wYear, cur_time.wMonth, cur_time.wDay, cur_time.wHour, cur_time.wMinute, cur_time.wSecond);
    StringCchLength(write_buffer, _countof(write_buffer), &bytes_need_write);
    WriteFile(hFile, write_buffer, bytes_need_write * sizeof(TCHAR), &bytes_written, NULL);

    hServStatus.dwCheckPoint = 0;
    hServStatus.dwWin32ExitCode = NO_ERROR;
    hServStatus.dwServiceSpecificExitCode = 0;
    hServStatus.dwCurrentState = SERVICE_RUNNING;
    if (!SetServiceStatus(hSStat, &hServStatus)) {
        GET_ERROR_CODE(n);
        UTILS_RIF_WITH_LOG(FALSE, LOG_LEVEL_ERROR, __SDFILE__, __LINE__, 
            TEXT("Set service status failed. Reason: %s\n"), 
            utils_format_error_string(n));
    }

    // block here until service stop
    while (!service_terminate) {
        Sleep(1000);
    }

    // stop service
    GetLocalTime(&cur_time);
    StringCchPrintf(write_buffer, _countof(write_buffer), TEXT("TestServ stopped, write time: %d-%d-%d %d:%d:%d\n"), 
        cur_time.wYear, cur_time.wMonth, cur_time.wDay, cur_time.wHour, cur_time.wMinute, cur_time.wSecond);
    StringCchLength(write_buffer, _countof(write_buffer), &bytes_need_write);
    WriteFile(hFile, write_buffer, bytes_need_write * sizeof(TCHAR), &bytes_written, NULL);
    CloseHandle(hFile);

    hServStatus.dwCheckPoint = 0;
    hServStatus.dwWin32ExitCode = NO_ERROR;
    hServStatus.dwServiceSpecificExitCode = 0;
    hServStatus.dwCurrentState = SERVICE_STOPPED;
    if (!SetServiceStatus(hSStat, &hServStatus)) {
        GET_ERROR_CODE(n);
        UTILS_RIF_WITH_LOG(FALSE, LOG_LEVEL_ERROR, __SDFILE__, __LINE__, 
            TEXT("Set service status failed. Reason: %s\n"), 
            utils_format_error_string(n));
    }
    
    return;
}

有几个关键点：

A. hServStatus是一个SERVICE_STRUCTURE，这个structure非常重要，定义了很多关键的数据。主要是：

(1) dwControlAccepted，不支持PAUSE和CONTINUE就不要写上。 

(2) dwWin32ExitCode这个member容易混淆。如果当前service的状态是PENDING（start pending/pause pending/continue pending/stop pending），那么可以设置为ERROR_SERVICE_SPECIFIC_ERROR， 这表示pending的时候如果出错了，让windows SCM去check dwServiceSpecificExitCode member来得到出错码。但是如果状态已经成功转换到了RUNNING/STOPPED，那么，要设置这个dwWin32ExitCode为NO_ERROR，此时windows SCM认为service状态转换没有错误发生，dwServiceSpecificExitCode的值被ignore。如果dwWin32ExitCode还为ERROR_SERVICE_SPECIFIC_ERROR的话，windows SCM就会认为service状态转换出错，然后把dwServiceSpecificExitCode作为出错码取出来报告。这就是为什么上面代码中，RUNNING和STOPPED状态转换完成的时候，要设置这两个member的原因。

(3) dwCheckPoint，也是用于pending状态的。pending状态的时候，windows SCM要知道service当前是否alive，依靠的就是周期性的check这个dwCheckPoint member。所以，我们的service在pending状态的时候，要经常使用SetServiceStatus来更新这个dwCheckPoint，否则windows SCM会认为service down，从而强制stop service。此外，当service完成pending状态切换到新状态后，记得重置dwCheckPoint为0.

(4) dwWaitHint，这个member定义一个时间（单位毫秒），在service处于pending状态时，如果过了这里定义的时间，windows SCM发现service的dwCheckPoint没有更新，或者service没有切换到新的非pending状态，那么，windows SCM就会强制stop service。

B. RegisterServiceCtrlHandlerEx函数。用来注册SCM动作的响应函数。也就是stop/continue这些命令的响应。例子： 

/*    Control Handler Function */
#ifdef RegisterServiceCtrlHandlerEx
DWORD WINAPI ServerCtrlHandlerEx( DWORD dwControl, DWORD dwEventType,
                              LPVOID lpEventData, LPVOID lpContext)
#else
DWORD WINAPI ServerCtrlHandler( DWORD dwControl)
#endif
 // requested control code 
{
    DWORD n;

    switch (dwControl) {
    case SERVICE_CONTROL_SHUTDOWN:
    case SERVICE_CONTROL_STOP:
        service_terminate = TRUE;
        hServStatus.dwCheckPoint++;
        hServStatus.dwWin32ExitCode = ERROR_SERVICE_SPECIFIC_ERROR;
        hServStatus.dwServiceSpecificExitCode = 0;
        hServStatus.dwCurrentState = SERVICE_STOP_PENDING;
        if (!SetServiceStatus(hSStat, &hServStatus)) {
            GET_ERROR_CODE(n);
            UTILS_RVIF_WITH_LOG(FALSE, NO_ERROR, LOG_LEVEL_ERROR, __SDFILE__, __LINE__, 
                TEXT("Set service status failed. Reason: %s\n"), 
                utils_format_error_string(n));
        }
        return NO_ERROR;
    case SERVICE_CONTROL_PAUSE:
        break;
    case SERVICE_CONTROL_CONTINUE:
        break;
    case SERVICE_CONTROL_INTERROGATE:
        return NO_ERROR;
    default:
        if (dwControl > 127 && dwControl < 256) /* User Defined */
        break;
    }
    return ERROR_CALL_NOT_IMPLEMENTED;
}

 

(1) 对于没有handle的control命令，return ERROR_CALL_NOT_IMPLEMENTED，对于handle的，返回NO_ERROR。例外是对于SERVICE_CONTROL_INTERROGATE，也要返回NO_ERROR，即使我们没有handle这个control。更具体的信息查看MSDN。

(2) SERVICE_CONTROL_SHUTDOWN是系统关机的时候SCM发送给service的。和SERVICE_CONTROL_STOP一样，可以在这里设置一个pending状态，在ServiceMain中真正stop了，设置STOPPED状态。

4. service本身的关键代码就是这些，下面是使用SCM如何创建一个service： 

#define SVCNAME TEXT("EricTestService")

int _tmain(int argc, PTSTR argv[], PTSTR env[])
{
    DWORD errcode = 0;
    SC_HANDLE hManager = NULL;
    SC_HANDLE hService = NULL;

    setlocale(LC_ALL, "CHS");

    // Open SCManager
    hManager = OpenSCManager(NULL, NULL, SC_MANAGER_ALL_ACCESS);
    if (NULL == hManager) {
        errcode = GetLastError();
        _tprintf(TEXT("Open service manager failed. Reason: %s\n"), utils_format_error_string(errcode));
        goto failed;
    }

    // create service
    hService = CreateService( 
        hManager,                   // SCM database 
        SVCNAME,                   // name of service 
        SVCNAME,                   // service name to display 
        SERVICE_ALL_ACCESS,        // desired access 
        SERVICE_WIN32_OWN_PROCESS, // service type 
        SERVICE_AUTO_START,      // start type 
        SERVICE_ERROR_NORMAL,      // error control type 
        TEXT("C:\\ScheduleDownload\\Practise\\TestServ\\Debug\\TestServ.exe"),  // path to service's binary 
        NULL,                      // no load ordering group 
        NULL,                      // no tag identifier 
        NULL,                      // no dependencies 
        NULL,                      // LocalSystem account 
        NULL);                     // no password

    if (NULL == hService) {
        errcode = GetLastError();
        _tprintf(TEXT("Create service failed. Reason: %s\n"), utils_format_error_string(errcode));
        CloseServiceHandle(hManager);
        goto failed;
    }

    CloseServiceHandle(hService);
    CloseServiceHandle(hManager);

    return 0;

failed:
    // wait key
    _getch();
    return 1;
}

这就比较简单了，使用OpenSCManager打开SCM，使用CreateService创建一个service，此时在windows的服务中就能看到了。start type中，设定为SERVICE_AUTO_START就会在开机时启动（不需要用户登录就会启动的，已经测试过了）。其他的函数比如StartService/DeleteService/QueryService...看看MSDN就OK了。