Good, I would like to know if there is a routine in PHP or Java Script that allows me to detect if an external application is open [closed]

You can do that if you are running PHP on your computer. The exec command in php allows you to execute operating system commands and obtain the output in a variable.

In windows you can execute the tasklist command and then parse the result lines obtained in the second parameter of the function.

$salida = array();
exec('tasklist', $salida);
print_r($salida);

PHP exec