Writing to /dev/ttyS

[Raja.Hayek@xxxxxxxxxxxxxx]

I am trying to write data through a
serial com port, but continuously get an error returned by the function
call. Basically, my code is simple and looks like this:

// includes go here
int main()
{
        int
res, fd1;
        char
buf1[255];

        fd1
= open("/dev/ttyS2", O_RDWR| O_NOCTTY | O_NDELAY);

        printf("fd1
= %d\n", fd1);

        //
prepare outgoing message
        sprintf(buf1,
"this is a test", sizeof("this is a test"));

        res
= write(fd1, buf1, strlen(buf1));
        printf("res
= %d, errno = %d\n", res, errno);

        return
0;
}

When I run the program, res comes up
as -1 and errno as 9 (EBADF). When I checked the value of this EBADF, it
turned out to be  "fd is not a valid file descriptor or is not
open for writing".
This is the output I get:
fd1 = 3
buf1 : this is a test
res = -1, errno = 9


Although here is what I get when I check
the settings of that port with setserial:

# setserial -g /dev/ttyS2
/dev/ttyS2, UART: 16650, Port: 0x03e8,
IRQ: 4

which appears to be OK, plus the fact
that the open() command returned a value of 3 for the file descriptor.

TIA.