Change flask running port in VScode debugger

I do have a flask application running on port 8000 because i have logstash running on port 5000.

app.run(debug=True, host='0.0.0.0', port=8000)

i can run my app successfully. but when i use VScode debugger it throws

OSError: [Errno 98] Address already in use

because the debugger tries to run my app on port 5000. i tried editing .vscode/launch.json and set "port": 8000 inside configurations but the error still the same. how can i tell the VScode to run my app with debugger on another port?