5000
Flask development server or UPnP control port
Flask Development Server / UPnP
What is port 5000?
Port 5000 is primarily known as the default Flask (Python) development server port (flask run). It is also used by the UPnP (Universal Plug and Play) control point protocol and Docker Registry. On macOS Monterey and later, this port is used by the AirPlay Receiver, which can cause conflicts with Flask development servers — a common frustration for macOS developers.
Quick checks
$
nc -zv example.com 5000
$
nmap -p 5000 example.com
$
telnet example.com 5000