Reading SMS messages from sim via serial port in Linux using C

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C

Linux

ATCommands

Hi,
am trying to read sms messages via serial port in linux a from a sim card which i have placed inside a huawei 3g usb modem. i have to execute the script a number of time before some of the sms messages are displayed on the screen. At times it displays unusual characters. All i want to do is read sms messages from the sim using AT commands, c and serial port. Below is the code i am using.

#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <termios.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <time.h>
#include <errno.h>

int main(){
    int fd;
    struct termios options;

    /* open the port */
    fd = open("/dev/ttyUSB0", O_RDWR | O_NOCTTY | O_NDELAY);
	if (fd == -1)
	   {                                              /* Could not open the port */
	     fprintf(stderr, "open_port: Unable to open /dev/ttyS1 - %s\n",strerror(errno));
	   }else{
		printf("port opened\n");
	    }
    fcntl(fd, F_SETFL, 0);

    /* get the current options */
    tcgetattr(fd, &options);

    /* set raw input, 1 second timeout */
    options.c_cflag     |= (CLOCAL | CREAD);
    options.c_lflag     &= ~(ICANON | ECHO | ECHOE | ISIG);
    options.c_oflag     &= ~OPOST;
    options.c_cc[VMIN]  = 0;
    options.c_cc[VTIME] = 10;

    /* set the options */
    tcsetattr(fd, TCSANOW, &options);

	char buffer[400];  /* Input buffer */
      char *bufptr;      /* Current char in buffer */
      int  nbytes;       /* Number of bytes read */
      int  tries;        /* Number of tries so far */

      for (tries = 0; tries < 1; tries ++)
      {
       /* send an AT command*/
	if (write(fd, "AT+CMGL=\"ALL\"\r", strlen("AT+CMGL=\"ALL\"\r")) < 3){
		printf("command sent\n");
	  continue;
	}

       /* read characters into our string buffer*/
	bufptr = buffer;

	nbytes = read(fd, bufptr, buffer + sizeof(buffer) - bufptr - 1);
	printf("%s\n",bufptr);

    char *p;

    p = strstr(buffer, "tin");
    printf("%s",p);

	p = strstr(buffer, "server");
	if(p == NULL) printf("not from server\n");

	*bufptr = '\0';

}
	return 0;
}