Serial Programming for POSIX, non-standard baud rate

Question

I am implementing a simple program in unix that takes a RS232 input and saves it into a file.

I've used these references: http://en.wikibooks.org/wiki/Serial_Programming/Serial_Linux http://www.easysw.com/~mike/serial/serial.html

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

int main(int argc,char** argv)
{
        struct termios tio;
        struct termios stdio;
        int tty_fd;
        fd_set rdset;
        FILE *file;

        unsigned char c;

        memset(&tio,0,sizeof(tio));
        tio.c_iflag=0;
        tio.c_oflag=0;
        tio.c_cflag=CS8|CREAD|CLOCAL;           // 8n1, see termios.h for more information
        tio.c_lflag=0;
        tio.c_cc[VMIN]=1;
        tio.c_cc[VTIME]=5;

        tty_fd=open("/dev/ttyS1", O_RDWR | O_NONBLOCK);      

        speed_t baudrate = 1843200; //termios.h: typedef unsigned long speed_t;
        cfsetospeed(&tio,baudrate);
        cfsetispeed(&tio,baudrate);

        tcsetattr(tty_fd,TCSANOW,&tio);

        file = fopen("out.raw", "wb");      

        while (1)
        {
                if (read(tty_fd,&c,1)>0) {
            fwrite(&c, 1, 1, file);
            fflush(file);
                }
        }

        //close(tty_fd);
}

I've tried at 921'600 bps and at 1'843'200 bps, and it works correctly. However, it does not work if I set-up a non-standard baud rate, for instance 1'382'400 bps.

i.e., this works: cfsetospeed(&tio,1843200); cfsetispeed(&tio,1843200);

but this doesn't (it gets random data): cfsetospeed(&tio,1382400); cfsetispeed(&tio,1382400);

---

What can be the problem?

I've tried with WinXP (using the WIN32 functions CreateFile, SetCommState and ReadFile), and it works correctly (with 1'843'200 bps and also with the non-standard 1'382'400 bps)

ps: if you ask why I need to set-up this non-standard baud-rate, it's because of a special machine that works only at this speed.

Regards, David