'16 bit assembly sending character to serial port

I created bridge on virtual serial ports(COM7 & COM8) with hdd device monitor studio and want to send and receive data with 16-bit assembly[using masm]. for beginning I wrote this code to send a character to COM7 and listen to this port but no thing transmit. I tested monitor of this port with sending data using another software. this is code:

.MODEL small
.STACK 100h
.data
.code
_start:
mov ax,@data
mov ds,ax
mov ah, 0           ;Initialize opcode
mov al, 11100011b   ;Parameter data.
mov dx, 6           ;COM7: port.
int 14h
again:
    mov  dx, 6           ;Select COM7:
    mov  al, 'm'        ;Character to transmit
    mov  ah, 1           ;Transmit opcode
    int  14h
    jmp again   
mov ah,1
int 21h
END _start

where is my wrong?

assemblyx86serial-portmasm


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