WonRhee

import sqlalchemy
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String, ForeignKey
from sqlalchemy.orm import sessionmaker, relationship


engine = sqlalchemy.create_engine('sqlite:///:memory:')
Base = declarative_base()

WonRhee

I have a web app that needs to talk to point of sale hardware: receipt printers, customer displays, 
cash drawers and payment terminals. Direct communication from the web app with these devices is 
impossible, so I created a native app that can be installed on the computer that can talk to the 
devices. The app runs a web server that exposes these devices using a REST api.

The native app registers itself upon startup with a webservice. It sends its own IP address on 
the local network and the server also sees the external IP address of the network. The web app 
sends a discovery request to the webservice and it receives all the local IP addresses which 
have the same external IP address.