Can't connect to Flask web service, connection refused

Run your app like this:

if __name__ == '__main__':
    app.run(host='0.0.0.0')

It will make the server externally visible. If the IP address of the machine is 192.168.X.X then, from the same network you can access it in 5000 port. Like, http://192.168.X.X:5000

when you are running the server via flask run change it to flask run --host=0.0.0.0 to connect, find the IPV4 address of the server that your script is running on. On the same network, go to http://[IPV4 address]:5000

A reason could also be in firewall refusing incoming connections on port 5000. Try:

sudo ufw allow 5000