请问：IFIFO读取数据失败

#define STR_TEST_FIFO_W        "fifo:/~/foobar?mode=w"

boolean BrewFifoWrite_InitAppData(BrewFifoWrite* pMe)
{
    int nRet = 0;
    pMe->DeviceInfo.wStructSize = sizeof(pMe->DeviceInfo);
    ISHELL_GetDeviceInfo(pMe->a.m_pIShell,&pMe->DeviceInfo);

    nRet = ISHELL_CreateInstance(pMe->a.m_pIShell, AEECLSID_FIFO, &pMe->m_pIFIFO);
    nRet = IFIFO_Open(pMe->m_pIFIFO, STR_TEST_FIFO_W);
    return TRUE;
}

void BrewFifoWrite_FreeAppData(BrewFifoWrite* pMe)
{
    IFIFO_Close(pMe->m_pIFIFO);
}

// 在按1的时候，对IFIFO写数据：
case EVT_KEY:
    switch (wParam)
    {
    case AVK_1:
    {
            PrintInfo(pMe->a.m_pIDisplay, szPost);
            Mms_StartPostMessage(pMe);
    }

// 写数据的实现：
void Mms_StartPostMessage(BrewFifoWrite* pMe)
{
    uint8                    DataBuffer[MAX_BUFFER_SIZE] = {'t', 'e', 's', 't', ' ', 'f', 'i', 'f', 'o', 0};
    int                        nRet;
    int                        nFileSize;

    // 向IFIFO中写数据
    nRet = IFIFO_Write(pMe->m_pIFIFO, DataBuffer, STRLEN(DataBuffer) * sizeof(uint8));
    // 启动读程序
    nRet = ISHELL_StartApplet(pMe->a.m_pIShell, AEECLSID_BREWFIFOREAD);
    // 发信号告诉读程序，可以读取消息了
    nRet = ISHELL_PostEvent(pMe->a.m_pIShell, AEECLSID_BREWFIFOREAD, UEVT_READ_FIFO, 0, 0);
}

// 在收到消息UEVT_READ_FIFO
case UEVT_READ_FIFO:
    Mms_StartGetMessage(pMe);
    return TRUE;

// 读IFIFO的实现
#define STR_TEST_FIFO_R        "fifo:/~/foobar?mode=r"
void Mms_StartGetMessage(BrewFifoRead* pMe)
{
    IFIFO*            pIFIFO;
    int                nRet;
    uint8*            pucDataBuffer;

    pucDataBuffer = (uint8*)MALLOC(sizeof(uint8) * MAX_BUFFER_SIZE);
    nRet = ISHELL_CreateInstance(pMe->a.m_pIShell, AEECLSID_FIFO, &pIFIFO);

    nRet = IFIFO_Open(pIFIFO, STR_TEST_FIFO_R);
    nRet = IFIFO_Read(pIFIFO, pucDataBuffer, MAX_BUFFER_SIZE);
    IFIFO_Close(pIFIFO);
    return;
}