Re: Newbie problem

[Bahadir Karuv <bahkar@bcacademies.bergen.org>]

Hi Ed,

Thanks for the speedy response. I thought the same but the first
computer keeps getting whatever it is sending ("Hello") eventhough the
serial cable is disconnected. The program I sent is running on the first
computer.

Thanks again and regards,

Karuv

Ed Vance wrote:

> Hi,
>
> My guess is that the second computer has "echo" enabled so all
> characters
> received are echoed back to the other end. I see you turn echo off in
> the
> program. I am assuming that the program is only running on the first
> computer.
>
> Regards,
> Ed
>
> ----------------------------------------------------------------
> Ed Vance              edv@macrolink.com
> Macrolink, Inc.       1500 N. Kellogg Dr  Anaheim, CA  92807
> ----------------------------------------------------------------
>
> -----Original Message-----
> From: Bahadir Karuv [mailto:bahkar@bcacademies.bergen.org]
> Sent: Thursday, April 25, 2002 8:59 AM
> To: linux-serial@vger.kernel.org
> Subject: Newbie problem
>
> Hello All,
>
> I am trying to have to computers communicate over the serial port.
> The program below is modified from "Serial Programming Guide for Posix
>
> operating Systems"
> I am geting the following output when I send "Testing123" over the
> serial port from the second computer
>
> opened 3
> just sent Hello
> got back - Hello
> just sent Hello
> got back - HelloTesting123
> just sent Hello
> got back - Hello
>
> First computer is getting the string echoed back to itself after it
> sends "Hello".
>
> What am I doing wrong?
>
> Thanks and regards!
>
>
>
> #include <stdio.h>
> #include <unistd.h>
> #include <fcntl.h>
> #include <termios.h>
> #include <string.h>
>
> int main(void)   /* Serial port */
>        {
>  time_t tsec;
>  int fd;
>  struct termios options;
>  char buffer[255];
>  char *bufptr;
>  int  nbytes;
>  char *message="Hello";
>
>  /* open the port */
>  fd = open("/dev/ttyS0", O_RDWR | O_NOCTTY | O_NDELAY);
>  //fcntl(fd, F_SETFL, FNDELAY);
>  printf("opened %u\n",fd);
>  /* options */
>  tcgetattr(fd, &options);
>  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;
>  tcsetattr(fd, TCSANOW, &options);
>  /* read characters into our string buffer until CR or NL */
>  while(1){
>  write(fd, message,strlen(message));
>  printf("just sent %s\n",message);
>  tsec=time(NULL);
>  while(time(NULL)-tsec<1);
>
>  bufptr = buffer;
>  buffer[0]='\0';
>  while ((nbytes = read(fd, bufptr, bufptr-buffer + sizeof(buffer)-1))
> >
> 0)
>  {
>   bufptr += nbytes;
>   if (bufptr[-1] == '\n' || bufptr[-1] == '\r')
>    { printf("break\n");break;}
>  }
>  if (buffer!=bufptr){
>    *(bufptr) = '\0';
>    printf("got back - %s\n",buffer);
>  }
>     }
>     close(fd);
> }
>
>
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