stm32f4 read data from pc's com port

I managed to send via stm32f4 data using usb and vcp.What i am trying to do now is to read data from pc .In order to check what is read through usb i send it again to the pc.

#define HSE_VALUE ((uint32_t)8000000) /* STM32 discovery uses a 8Mhz external crystal */
#include ''stm32f4xx_conf.h''
#include ''stm32f4xx.h''
#include ''stm32f4xx_gpio.h''
#include ''stm32f4xx_rcc.h''
#include ''stm32f4xx_exti.h''
#include ''usbd_cdc_core.h''
#include ''usbd_usr.h''
#include ''usbd_desc.h''
#include ''usbd_cdc_vcp.h''
#include ''usb_dcd_int.h''
volatile uint32_t ticker, downTicker;
/*
* The USB data must be 4 byte aligned if DMA is enabled. This macro handles
* the alignment, if necessary (it's actually magic, but don't tell anyone).
*/
__ALIGN_BEGIN USB_OTG_CORE_HANDLE USB_OTG_dev __ALIGN_END;
void init();
void ColorfulRingOfDeath(void);
/*
* Define prototypes for interrupt handlers here. The conditional ''extern''
* ensures the weak declarations from startup_stm32f4xx.c are overridden.
*/
#ifdef __cplusplus
extern ''C'' {
#endif
void SysTick_Handler(void);
void NMI_Handler(void);
void HardFault_Handler(void);
void MemManage_Handler(void);
void BusFault_Handler(void);
void UsageFault_Handler(void);
void SVC_Handler(void);
void DebugMon_Handler(void);
void PendSV_Handler(void);
void OTG_FS_IRQHandler(void);
void OTG_FS_WKUP_IRQHandler(void);
#ifdef __cplusplus
}
#endif
int main(void)
{ uint8_t theByte[1];
theByte[0]=123;
//theByte[1]=95;
/* Set up the system clocks */
SystemInit();
/* Initialize USB, IO, SysTick, and all those other things you do in the morning */
init();
GPIO_SetBits(GPIOD,GPIO_Pin_14);
while (1)
{
VCP_get_string(&theByte);
VCP_send_buffer(&theByte, 1);
}
}
void init()
{
/* STM32F4 discovery LEDs */
GPIO_InitTypeDef LED_Config;
/* Always remember to turn on the peripheral clock... If not, you may be up till 3am debugging... */
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOD, ENABLE);
LED_Config.GPIO_Pin = GPIO_Pin_12 | GPIO_Pin_13| GPIO_Pin_14| GPIO_Pin_15;
LED_Config.GPIO_Mode = GPIO_Mode_OUT;
LED_Config.GPIO_OType = GPIO_OType_PP;
LED_Config.GPIO_Speed = GPIO_Speed_25MHz;
LED_Config.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_Init(GPIOD, &LED_Config);
/* Setup SysTick or CROD! */
if (SysTick_Config(SystemCoreClock / 1000))
{
ColorfulRingOfDeath();
}
/* Setup USB */
USBD_Init(&USB_OTG_dev,
USB_OTG_FS_CORE_ID,
&USR_desc,
&USBD_CDC_cb,
&USR_cb);
return;
}
/*
* Call this to indicate a failure. Blinks the STM32F4 discovery LEDs
* in sequence. At 168Mhz, the blinking will be very fast - about 5 Hz.
* Keep that in mind when debugging, knowing the clock speed might help
* with debugging.
*/
void ColorfulRingOfDeath(void)
{
uint16_t ring = 1;
while (1)
{
uint32_t count = 0;
while (count++ < 
500000
);
GPIOD->BSRRH = (ring << 
12
);
ring
= ring << 1;
if (ring >= 1<<
4
)
{
ring
= 
1
;
}
GPIOD->BSRRL = (ring << 
12
);
}
}
/*
* Interrupt Handlers
*/
void SysTick_Handler(void)
{
ticker++;
if (downTicker > 0)
{
downTicker--;
}
}
void NMI_Handler(void) {}
void HardFault_Handler(void) { ColorfulRingOfDeath(); }
void MemManage_Handler(void) { ColorfulRingOfDeath(); }
void BusFault_Handler(void) { ColorfulRingOfDeath(); }
void UsageFault_Handler(void){ ColorfulRingOfDeath(); }
void SVC_Handler(void) {}
void DebugMon_Handler(void) {}
void PendSV_Handler(void) {}
void OTG_FS_IRQHandler(void)
{
USBD_OTG_ISR_Handler (&USB_OTG_dev);
}
void OTG_FS_WKUP_IRQHandler(void)
{
if(USB_OTG_dev.cfg.low_power)
{
*(uint32_t *)(0xE000ED10) &= 0xFFFFFFF9 ;
SystemInit();
USB_OTG_UngateClock(&USB_OTG_dev);
}
EXTI_ClearITPendingBit(EXTI_Line18);
}