A question about programming RS-232

[Сергей Собко]

Hello.
I have a question I can't deal myself.
And nobody can help me in resolving my problem.

Problem:
I have a hand-made device, I want to control from FreeBSD 6.1
(I am porting this application from Windows equivalent).
But I don't know, in what device /dev/ I should write to get reults.
I tryed to write bytes into /dev/ttyd0, /dev/cuad0, but got nothing. :(

Code:

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

int main(void) {
 int t = 0, num = 10, fd, i, iOut; char *ch;
 struct termios my_termios;
 ch = (char *)malloc(6);
 memset(ch, 250, 6);
 fd = open("/dev/ttyd0", O_RDWR | O_NONBLOCK);
 printf("Opened com port\n");
 if(fd < 0) return 0;
// tcflush(fd, TCIFLUSH);
 my_termios.c_cflag = CS8 | CLOCAL;
 if(cfsetspeed(&my_termios, B9600) < 0) return 0;
 if(tcsetattr(fd, TCSANOW, &my_termios) < 0) return 0;
 iOut = write(fd, ch, 6);
 if(iOut < 0) return 0;
 printf("Number of bytes = %d\n", iOut);
 printf("Writed %s!\n", ch);
 close(fd);
 printf("Closed!\n");
 return 0;
}

P.S. Please, help me. 
P.P.S. Sorry for such stupid and annoying questions
P.P.P.S. Sorry for my bad English as I'm from Russia and I'm only 16 ;)