:: version 1.0
echo off
set PORT=8081
set RULE_NAME="Open Port %PORT%"
cls
for /f "skip=1 tokens=2 delims=: " %%a in ('nslookup google.com ^| find /v "Aliases"') do set my_dns_result=%%a

echo Result from Your DNS Settings : %my_dns_result%

netsh advfirewall firewall show rule name=%RULE_NAME% >nul
if not ERRORLEVEL 1 (
    netsh advfirewall firewall set rule name=%RULE_NAME% new remoteip=%my_dns_result%
    echo Remote-IP updated.
) else (
    echo Rule %RULE_NAME% does not exist. Creating...
    netsh advfirewall firewall add rule name=%RULE_NAME% dir=in action=allow protocol=TCP localport=%PORT% remoteip=%my_dns_result%
)