COM to COM chat

[5888]

Hello there.

I am trying to write a chat program through the serial com port. Unfortunately, the following code that allows me to send a character at one time. So I am not able to type an English word and send it to the other side.

For example if i would like to send "Hello" from PC-A to PC-B, I have to type "H" and then wait for PC-B to press a key then only I can type "e".

The whole process is like PC-A sends one character, then PC-B has to response and send a character back to PC-A so that PC-A can send the second character to PC-B.

I do not know what happen to the following code, logically it makes sense but......please help. Thank you

.MODEL SMALL
.STACK 64
.DATA
MESSAGE DB 'Serial communication via COM2,4800,No P,1 Stop,8-BIT
DATA.',0AH,0DH
DB 'ANY KEY PRESS IN SENT TO OTHER PC.',0AH,0DH
DB 'PRESS ESC TO EXIT','$'

.CODE
MAIN PROC
MOV AX,@DATA
MOV DS,AX
MOV AH,09
MOV DX,OFFSET MESSAGE
INT 21H ;initializing COM2
MOV AH,0 ;initialize COM port
MOV DX,01 ;COM 2
MOV AL,0E3H ;4800,NO P,1 STOP,8-BIT DATA
INT 14H ;checking key press and sending key to COM2 to
be transfered

AGAIN:

MOV AH,01 ;check for key press using INT 16H,AH=01
INT 16H ;if ZF=1,there is no key press
JZ NEXT ;if no key go check COM port
MOV AH,0 ;yes,there is a key press,get it
INT 16H ;notice we must use INT 16H twice,2nd time
;with AH=0 to get the char itself.AL=ASCII char pressed
CMP AL,1BH ;is it esc key?
JE EXIT ;yes EXIT

MOV AH,1 ;no.send the char to COM 2 port
MOV DX,01
INT 14H ;check COM2 port to see there is char, if so get
it and display it

mov ah, 0
int 16h

NEXT: MOV AH,03 ;get COM2 status
MOV DX,01
INT 14H
AND AH,01 ;AH has COM port status, mask all bits except D0
CMP AH,01 ;check D0 to see if there is a char
JNE AGAIN ;no data, go to monitor keyboard
MOV AH,02 ;yes,COM2 has data:get it
MOV DX,01
INT 14H ;get it
MOV DL,AL ;and display it using INT 21H
MOV AH,02 ;DL has char to be displayed
INT 21H

JMP AGAIN ;keep monitoring keyboard
EXIT: MOV AH,4CH ;exit to DOS
INT 21H

MAIN ENDP
END main