problem with serial port communication

[abhinav123]

I am working on an embeeded device.i connect to it using COM port.
It gives the list of all files when i send a command "LIST" to it.

so i wrote an "hello world" which will connect to the port device is connected and will send data.

When i connect my device and run my program it is writing to the port and not receiving any bytes from the port.

but when i open the COM port using PUTTY(which is used to open port and send some data) and send COMMAND it works and when i CLOSE PUTTY and NOW RUN MY PROGRAM now it is working fine,so there is some initialisation to the port which i am missing.

can anyone help me out in this,i am unable to find solution for the past day.thanks in advance...


my program is:-

#include "stdafx.h"
#include <iostream>
#include <afx.h>

int main()
{
	using namespace std;
	int i=0;
//	cout << "Hello world!" << endl;



	HANDLE hSerial;

	hSerial = CreateFile("COM5",
	GENERIC_READ | GENERIC_WRITE,
	FILE_SHARE_WRITE | FILE_SHARE_READ,
	0,
	OPEN_EXISTING,
	FILE_ATTRIBUTE_NORMAL,
	0);

	if(hSerial==INVALID_HANDLE_VALUE)
	{
		if(GetLastError()==ERROR_FILE_NOT_FOUND)
		{
//			TRACE("serial port does not exist for reading\n");
		//serial port does not exist. Inform user.
		}
//			TRACE("some other error,serial port does not exist for reading\n");
		//some other error occurred. Inform user.
	}

	DCB dcbSerialParams = {0};

	dcbSerialParams.DCBlength=sizeof(dcbSerialParams);

	if (!GetCommState(hSerial, &dcbSerialParams)) 
	{
//					TRACE("error getting state for reading\n");
	//error getting state
	}

	dcbSerialParams.BaudRate=9600;
	dcbSerialParams.ByteSize=8;
	dcbSerialParams.StopBits=ONESTOPBIT;
	dcbSerialParams.Parity=NOPARITY;
	dcbSerialParams.fOutX=TRUE;
	dcbSerialParams.fInX=TRUE;
	if(!SetCommState(hSerial, &dcbSerialParams))
	{
	//TRACE("error setting state for reading\n");
	//error setting serial port state
	}
	COMMTIMEOUTS timeouts={0};

	timeouts.ReadIntervalTimeout=50;
	timeouts.ReadTotalTimeoutConstant=50;
	timeouts.ReadTotalTimeoutMultiplier=10;

	timeouts.WriteTotalTimeoutConstant=50;
	timeouts.WriteTotalTimeoutMultiplier=10;

	if(!SetCommTimeouts(hSerial, &timeouts))
	{
//					TRACE("some error occured for reading\n");
		//error occureed. Inform user
	}		
	int n=100,n1=100;
	char szBuff[100];
	DWORD dwBytesRead = 0;
	char szBuff1[100];
	DWORD dwByteswrote = 0;
	memset(szBuff1,0,100);
	memcpy(szBuff1,"LIST\r",5);
	FlushFileBuffers(hSerial);
	LPDWORD uf=0;
	GetCommModemStatus(hSerial,uf);
	TRACE("&#37;d\n",uf);
	if(!WriteFile(hSerial, szBuff1,5, &dwByteswrote, NULL))
	{
					cout << "error writing" ;
	}
	cout << szBuff1 << endl;
	cout << dwByteswrote << endl;
	dwByteswrote=0;
	while(1)
	{
		if(!ReadFile(hSerial, szBuff, n1, &dwBytesRead, NULL))
		{
			cout << "error reading";
			break;
		}
		else
		{
			cout << dwBytesRead << endl;
			szBuff[dwBytesRead]='\0';
			if(dwBytesRead>0)
			{
				cout << (szBuff);

				break;
			}
			else
			{
					if(!WriteFile(hSerial, szBuff1,5, &dwByteswrote, NULL))
					{
						cout << "error writing" ;
					}
					cout << dwByteswrote << endl;
			}
		}
	}
	cin >> i;
}