Thread: Error while reading data from serial port

I am writing a program in Visual C++ to access serial port.Code is given below:-

Code:

    #include "stdafx.h"
    #include <windows.h>
    #include <stdlib.h>
    #include <stdio.h>
    #include <string.h>
    #include <commdlg.h>


    int nread,nwrite;




    void main()
    {


     COMMTIMEOUTS timeouts;
     COMMCONFIG dcbSerialParams;
     char *words,*buffRead, *buffWrite;
     DWORD dwBytesWritten,dwBytesRead;






     HANDLE hSerial= CreateFile(L"COM1", GENERIC_READ | GENERIC_WRITE,
                           0,0,OPEN_EXISTING,FILE_ATTRIBUTE_NORMAL,0);
     if ( hSerial == INVALID_HANDLE_VALUE) 
     {
     if (GetLastError() == ERROR_FILE_NOT_FOUND)
     {
     printf(" serial port does not exist \n");
     }
     printf(" some other error occured. Inform user.\n");
     }




     //DCB     dcbSerialParams ;
     //GetCommState( hSerial, &dcbSerialParams.dcb);
     if (!GetCommState(hSerial, &dcbSerialParams.dcb)) 
     {
     printf("error getting state \n");
     }


     dcbSerialParams.dcb.DCBlength = sizeof(dcbSerialParams.dcb);




     dcbSerialParams.dcb.BaudRate = CBR_1200;
     dcbSerialParams.dcb.ByteSize = 8;
     dcbSerialParams.dcb.StopBits = ONESTOPBIT;
     dcbSerialParams.dcb.Parity = NOPARITY;


     dcbSerialParams.dcb.fBinary = TRUE;
     dcbSerialParams.dcb.fDtrControl = DTR_CONTROL_DISABLE;
     dcbSerialParams.dcb.fRtsControl = RTS_CONTROL_DISABLE;
     dcbSerialParams.dcb.fOutxCtsFlow = FALSE;
     dcbSerialParams.dcb.fOutxDsrFlow = FALSE;
     dcbSerialParams.dcb.fDsrSensitivity= FALSE;
     dcbSerialParams.dcb.fAbortOnError = TRUE;




    if (!SetCommState(hSerial, &dcbSerialParams.dcb)) 
    {
    printf(" error setting serial port state \n");
    }




    GetCommTimeouts(hSerial,&timeouts);


    timeouts.ReadIntervalTimeout = 1000;
    timeouts.ReadTotalTimeoutConstant = 1000;
    timeouts.ReadTotalTimeoutMultiplier = 1000;
    timeouts.WriteTotalTimeoutConstant = 1000;
    timeouts.WriteTotalTimeoutMultiplier= 1000;


    if(!SetCommTimeouts(hSerial, &timeouts)) 
    {
    printf("error setting port state \n");
    }




    //****************Write Operation*********************//
    words = "B";
    nwrite = strlen(words);


    buffWrite = words;
    dwBytesWritten = 0;


    if (!WriteFile(hSerial, buffWrite, nwrite, &dwBytesWritten, NULL)) 
    { 
    printf("error writing to output buffer \n");
    }
    printf("Data written to write buffer is\n %s \n",buffWrite);










    //***************Read Operation******************//
    buffRead = 0;
    dwBytesRead = 0;
    nread = strlen(words);


    if (!ReadFile(hSerial, buffRead, nread, &dwBytesRead, NULL)) 
    {
    printf("error reading from input buffer \n");
    }
    printf("Data read from read buffer is \n %s \n",buffRead);


    CloseHandle(hSerial);


    }

Above program is working properly while write operation (i.e writing data on serial port) but while read operation its is not reading data from serial port.


I am getting output on console window is given below:-

Code:

    Data written to write buffer is
    B
    error reading from input buffer
    Data read from read buffer is
    <null>

I want to know where I am getting wrong and how to resolve it.

Originally Posted by Saad Rafey

Code:

void main()

this is the first mistake that immediately stood out to me. the correct form is

Code:

int main()

or

int main(int argc, char** argv)

the second mistake you made was posting C code in the C++ forum. an alternative to this would be to post in the windows forum, as you are clearly using windows-specific system calls.

@Elkvis thanks for your help