Problem sending modem commands to modem.

Hello,

I am writing a C program to enable my modem for caller id and extract the data.  However, when I send some data to the modem, nothing happens, even though I have got a connection with the modem?  I am compiling this under Suse Linux 8.2 using Kdevelop 2.1.  If I use Hyperterminal under windows, I can enter the same commands and get the caller id from the modem when the phone rings.  I am using a baud rate of 2400 when I use hyperterminal - the same in my program.  I do not know why it is not working???  I know there are problems in the code (an infinite loop), but I just want to be able to send the stringsto the modem and get that working first!

Any help would be appreciated with this problem.

Kind Regards,

David.



#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdio.h>
#include <fcntl.h>
#include <termios.h>
#include <sys/types.h>
#include <sys/stat.h>


#define BAUDRATE B2400
#define SERIALPORT "/dev/ttyS0"    // I have got rw access to this port.

int main()
{
  int openPortResult, readResult, output;
  struct termios newTio;
  char tempBuffer[100];

  printf ("\n going to open modem device ....\n");
  openPortResult = open(SERIALPORT, "w+");
  if (openPortResult < 0)
  {
    perror(SERIALPORT);
    exit(-1);
  }

  printf("\nmodem device %d\n", openPortResult);  // OpenPortResult is assigned the value of 9

  tcgetattr(openPortResult,&newTio);
  newTio.c_cflag = BAUDRATE | CRTSCTS | CS8 | CLOCAL | CREAD | HUPCL;
  newTio.c_iflag = IGNBRK | IGNPAR;

  output = tcsetattr(openPortResult,TCSANOW,&newTio);
  printf("\nsetting serial port details...  value: %d\n", output); //output displays value of 0.
 
  output = write (openPortResult, "AT");
  printf("\nAT output is: %d\n", output);   //output = -1 - I cannot ping the modem!
  output = write (openPortResult, "ATZ");
  printf("\nATZ output is: %d\n", output);  //output = -1
  output = write (openPortResult, "AT+GCI=B4");
  printf("\nAT+GCI=B4 output is: %d\n", output);  //output = -1
  output = write (openPortResult, "AT+VCID=1");
  printf("\nAT+VCID=1 output is: %d\n", output);  //output = -1

  //Infinite loop - just trying to get it to display something (not -1)
  while (1)
  {
    readResult = read(openPortResult, tempBuffer, 100);
    tempBuffer[readResult]=0;
    printf(":%s:%d\n", tempBuffer, readResult); //yep you guessed it -1 again!
  }

  output = close(SERIALPORT);  //will never be called!
 
  return 0; //will never return.
}