DOS Int14 Service 04 Serial Question

[deanlwvu]

I'm trying to pull a character from the serial port, and I'm having some trouble. I need to have a program listen to the serial port and print a character if it sees one, or send a character out if a key is pressed. Using Turbo C 2.1 on a Windows 2k machine.

/* -- Includes -- */

#include <stdio.h>
#include <dos.h>

/* -- Function Prototypes -- */

int initialize_serial_port(void);
void serial_out(unsigned char);
unsigned char serial_in(void);

int main()
{
	unsigned char key_out = 0;
	unsigned char key_in = 0;
	int serial_status = 0;
	system("CLS");
	gotoxy(0,0);

	serial_status = initialize_serial_port();

	if (serial_status == 1)
	{
        	while(key_out != 27)	/* Looking for an ESC character */
		{

			if (kbhit())
			{
				key_out = getch();
				serial_out(key_out);
			}


			key_in = serial_in();
			if (key_in != NULL)
			{
				printf("%c", key_in);
			}

		}
	}
	return 0;
}

int initialize_serial_port()		/* Setting serial port up for COM2, 9600, 8, N, 1 */
{
	_AH = 04;
	_AL = 00;
	_DX = 00;
	_BH = 00;
	_BL = 00;
	_CH = 03;
	_CL = 07;
	geninterrupt(0x14);
	return 1;
}

void serial_out(unsigned char key)	/* Sends data out one character at a time */
{
	_AH = 01;
	_AL = key;
	_DX = 00;

	geninterrupt(0x14);
}

unsigned char serial_in(void)		/* Checks serial port for data */
{
	_AH = 02;
	_DX = 00;

	geninterrupt(0x14);
	return _AL;
}