TM4C1294 ethernet Bootloader cannot send the bootp

Now i have custom board using tm4c1294kcpdt. I compiled the C:\ti\TivaWare_C_Series-2.1.3.156\examples\boards\dk-tm4c129x\boot_emac_flash\ code for ethernet bootloader. After Recv the magic pkt from LMFlash Program, my APP enter this line :

void SoftwareUpdateBegin(uint32_t ui32SysClock)
{
    //
    // Disable all processor interrupts.  Instead of disabling them
    // one at a time (and possibly missing an interrupt if new sources
    // are added), a direct write to NVIC is done to disable all
    // peripheral interrupts.
    //
    HWREG(NVIC_DIS0) = 0xffffffffU;
    HWREG(NVIC_DIS1) = 0xffffffffU;
    HWREG(NVIC_DIS2) = 0xffffffffU;
    HWREG(NVIC_DIS3) = 0xffffffffU;
    HWREG(NVIC_DIS4) = 0xffffffffU;

    //
    // Also disable the SysTick interrupt.
    //
    SysTickIntDisable();
    SysTickDisable();

    //
    // Return control to the boot loader.  This is a call to the SVC
    // handler in the flashed-based boot loader, or to the ROM if configured.
    //
#if ((defined ROM_UpdateEMAC) && !(defined USE_FLASH_BOOT_LOADER))
    ROM_UpdateEMAC(ui32SysClock);
#else
    (*((void (*)(void))(*(uint32_t *)0x2c)))();
#endif
}

then enter the bootloader, I check the code excute the Boopt send function by led in bootloader, but I cannot find any BOOTP in wireshark.

if i inserted the uart init code as following:

void
UpdateBOOTP(void)
{
    //
    // Get the size of flash.
    //
    g_ui32FlashEnd =  ROM_SysCtlFlashSizeGet();
#ifdef FLASH_RSVD_SPACE
    g_ui32FlashEnd -= FLASH_RSVD_SPACE;
#endif

    ROM_SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOD);
    ROM_GPIOPinTypeGPIOOutput(GPIO_PORTD_BASE, GPIO_PIN_0);
    FeedWatchDog();
#if 1
    ROM_GPIOPinConfigure(GPIO_PP0_U6RX);
    ROM_GPIOPinConfigure(GPIO_PP1_U6TX);
    ROM_GPIOPinTypeUART(GPIO_PORTP_BASE, GPIO_PIN_0 | GPIO_PIN_1);
    UARTStdioConfig(6, 115200, 120000000);

    //UARTprintf("<< UART print configured Enabled >>\n");
#endif
    //
    // Perform the common Ethernet configuration. The frequency should
    // match whatever the application sets the system clock.
    //
    EnetReconfig(120000000);
    FeedWatchDog();
    //
    // Main Application Loop.
    //
    while(1)
    {
        uint32_t ui32Temp;

        //
        // See if there is a packet waiting to be read.
        //
        if(!(g_psRxDescriptor[g_ui32RxDescIndex].ui32CtrlStatus &
             DES0_RX_CTRL_OWN))
        {
            //
            // Read the packet from the Ethernet controller.
            //
            uip_len = PacketReceive(uip_buf, UIP_CONF_BUFFER_SIZE);

the BOOTP came in, why this happened. So confusing.

UART6   for message send;

PortD pin0 for GPIO watch dog;

PortF pin0 and 4 for ethernet led.

the code is the same as C:\ti\TivaWare_C_Series-2.1.3.156\examples\boards\dk-tm4c129x\boot_emac_flash\.

boot_emac_flash.rar