WriteFile to a serial port always times out and the number of bytes written is zero

Question

I'm trying to send At commands to my mobile phone (Nokia 5130)

The phone is connected via a usb port (used in modem mode), so after I installed the driver I get it listed as a COM port on device manager (Nokia 5130 XPressMusic USB Serial Port (COM17))

Here is the code :

            #include <iostream>
    #include <Windows.h>

    using namespace std;

    int main()
    {
        HANDLE hport = INVALID_HANDLE_VALUE;
        DCB portConfig;

        hport = CreateFile( TEXT("\\\\.\\COM17"),GENERIC_READ | GENERIC_WRITE,  
            0,NULL,OPEN_EXISTING,0,0); 

        if(hport == INVALID_HANDLE_VALUE)
        {
            cout<<GetLastError();
            system("pause");
            return 0;
        }

        if(GetCommState(hport,&portConfig)==0)
        {
            cout<<"Erreur de recuperation de la configuration :"<<GetLastError()<<endl;
            system("pause");
            return 0;
        }

        portConfig.BaudRate = CBR_9600;
        portConfig.Parity = NOPARITY ;
        portConfig.StopBits = ONESTOPBIT;
        portConfig.ByteSize = 8;
        portConfig.fBinary = TRUE;
        portConfig.fDtrControl = DTR_CONTROL_HANDSHAKE;
        portConfig.fOutX = true;
        portConfig.fRtsControl = RTS_CONTROL_HANDSHAKE;
        portConfig.fAbortOnError = TRUE;
        portConfig.fParity = TRUE;

        if(SetCommState(hport,&portConfig)==0)
        {
            cout<<"Erreur de configuration Setcommstate:"<<GetLastError()<<endl;
            system("pause");
            return 0;
        }

        COMMTIMEOUTS comTimeOut;                
        comTimeOut.ReadIntervalTimeout = 3000;
        comTimeOut.ReadTotalTimeoutMultiplier = 3000;
        comTimeOut.ReadTotalTimeoutConstant = 2000;
        comTimeOut.WriteTotalTimeoutMultiplier = 3000;
        comTimeOut.WriteTotalTimeoutConstant = 2000;
        SetCommTimeouts(hport,&comTimeOut);

        DWORD  dwNumberOfBytesWritten;
        unsigned char * buffer = new unsigned char[4];
        buffer[0] = 'A';
        buffer[1] = 'T';
        buffer[2] = '\r';
        buffer[3] = '\n';


        WriteFile(hport,buffer,4,&dwNumberOfBytesWritten,NULL);
        cout<<"erreur "<<dwNumberOfBytesWritten<<" d'ecriture :"<<GetLastError();

        delete [] buffer;

        system("pause");
        CloseHandle(hport);
        return 0;
    }

Can anybody tell me why WriteFile doesn't write anything to the serial port ?

Is it because the com port is not a real com port (usb to com) ?
(NB : If I don't specify the timeout WriteFile just hangs)

portMon Dump :

        19  0.00002536  ConsoleApplica  IRP_MJ_CREATE   USBSER000   SUCCESS Options: Open   
        20  0.00047645  ConsoleApplica  IOCTL_SERIAL_GET_BAUD_RATE  USBSER000   SUCCESS     
        21  0.00035417  ConsoleApplica  IOCTL_SERIAL_GET_LINE_CONTROL   USBSER000   SUCCESS     
        22  0.00000045  ConsoleApplica  IOCTL_SERIAL_GET_CHARS  USBSER000   SUCCESS     
        23  0.00000045  ConsoleApplica  IOCTL_SERIAL_GET_HANDFLOW   USBSER000   SUCCESS     
        24  0.00032201  ConsoleApplica  IOCTL_SERIAL_GET_BAUD_RATE  USBSER000   SUCCESS     
        25  0.00022917  ConsoleApplica  IOCTL_SERIAL_GET_LINE_CONTROL   USBSER000   SUCCESS     
        26  0.00000091  ConsoleApplica  IOCTL_SERIAL_GET_CHARS  USBSER000   SUCCESS     
        27  0.00000000  ConsoleApplica  IOCTL_SERIAL_GET_HANDFLOW   USBSER000   SUCCESS     
        28  0.00071875  ConsoleApplica  IOCTL_SERIAL_SET_BAUD_RATE  USBSER000   SUCCESS Rate: 9600  
        29  0.00062953  ConsoleApplica  IOCTL_SERIAL_SET_LINE_CONTROL   USBSER000   SUCCESS StopBits: 1 Parity: NONE WordLength: 8  
        30  0.00000091  ConsoleApplica  IOCTL_SERIAL_SET_CHAR   USBSER000   SUCCESS EOF:0 ERR:0 BRK:0 EVT:0 XON:0 XOFF:0    
        31  0.00000045  ConsoleApplica  IOCTL_SERIAL_SET_HANDFLOW   USBSER000   SUCCESS Shake:80000042 Replace:81 XonLimit:0 XoffLimit:0    
        32  0.00000045  ConsoleApplica  IOCTL_SERIAL_SET_TIMEOUTS   USBSER000   SUCCESS RI:3000 RM:3000 RC:2000 WM:3000 WC:2000 
        33  14.00148370 ConsoleApplica  IRP_MJ_WRITE    USBSER000   TIMEOUT Length 4: ....  
        34  0.00000408  ConsoleApplica  IRP_MJ_CLEANUP  USBSER000   SUCCESS     
        35  0.00047464  ConsoleApplica  IRP_MJ_CLOSE    USBSER000   SUCCESS     

Answer 1

ok i solved this by changing the com port number even if COM17 is what is shown at device manager it was not the right port this has nothing to do with port configuration (default values work) that's it ! thanks everyone.