Unable to receive data through serial port

Hi All,

Currently I try to write a serial port communication in VC++ to transfer data from PC and robot via XBee transmitter. But after I wrote some commands to poll data from robot, I can not receive anything from the robot (the output of buffer is empty.). One problem may be that I have no idea how big of data I will receive from robot. So I am not sure whether I set the size of "buffer" to 257 is correct. In addition, the output of "error" is always 1. Because my MATLAB interface works, so the problem should happen in the code not the hardware or communication. Would you please give me help?

P.S (1) I have called GetLastError and err=WriteFile(...), they showed that no error happen in WriteFIle or ReadFIle.

      (2) The communication require that Flow control: "Hardware" for XBee, "None" for USB cable adapter. Would you please tell me whether I set the flow control correctly in the code?

#include "StdAfx.h"
#include <iostream>;
#define WIN32_LEAN_AND_MEAN //for GetCommState command
#include "Windows.h"
#include <WinBase.h>;

using namespace std;

int main(){
  
  char init[]="";

  HANDLE serialHandle;

  // Open serial port
  serialHandle = CreateFile("\\\\.\\COM8", GENERIC_READ | GENERIC_WRITE, 0, 0, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0);

// Do some basic settings
  DCB serialParams;
  DWORD read, written;
  serialParams.DCBlength = sizeof(serialParams);

  if((GetCommState(serialHandle, &serialParams)==0))
  {
	printf("Get configuration port has a problem.");
    return FALSE;
   }

   GetCommState(serialHandle, &serialParams);
   serialParams.BaudRate = CBR_57600;
   serialParams.ByteSize = 8;
   serialParams.StopBits = ONESTOPBIT;
   serialParams.Parity = NOPARITY;

   //set flow control="hardware"
   serialParams.fOutX=false;
   serialParams.fInX=false;
   serialParams.fOutxCtsFlow=true;
   serialParams.fOutxDsrFlow=true;
   serialParams.fDsrSensitivity=true;
   serialParams.fRtsControl=RTS_CONTROL_HANDSHAKE;
   serialParams.fDtrControl=DTR_CONTROL_HANDSHAKE;

   if (!SetCommState(serialHandle, &serialParams))
   {
	   printf("Set configuration port has a problem.");
       return FALSE;

   }


   GetCommState(serialHandle, &serialParams);

   // Set timeouts
   COMMTIMEOUTS timeout = { 0 };
   timeout.ReadIntervalTimeout = 3;
   timeout.ReadTotalTimeoutConstant = 3;
   timeout.ReadTotalTimeoutMultiplier = 3;
   timeout.WriteTotalTimeoutConstant = 3;
   timeout.WriteTotalTimeoutMultiplier = 3;

   SetCommTimeouts(serialHandle, &timeout);

   if (!SetCommTimeouts(serialHandle, &timeout))
   {
	   printf("Set configuration port has a problem.");
       return FALSE;

   }



   //write packet to poll data from robot
   WriteFile(serialHandle,">*>p4",strlen(">*>p4"),&written,NULL);


   //check whether the data can be received
  
   char buffer[257];

  if (!ReadFile(serialHandle,buffer,sizeof(buffer),&read,NULL))
  {
	  printf("Reading data to port has a problem.");
	  return FALSE;
  }
 int t;
 bool error;
 DWORD numberOfBytesRead=0;
 DWORD err = GetLastError();
  for (int jj=0;jj<10;jj++)
  {
	  error=ReadFile(serialHandle,LPVOID(buffer),255,&numberOfBytesRead,NULL);
	  buffer[numberOfBytesRead]=0;
	      cout<<buffer<<endl;
		  cout<<error;
  } 


  
   CloseHandle(serialHandle);
   return 0;
}