AndreSuryana/pos-simulator-ecr-ws ? reverse-engineered prompt

Build me a small Python app that simulates a POS terminal talking to an ECR over WebSocket.

I want it to let me start the simulator, connect to a websocket server, and send and receive basic transaction messages like payment requests, approvals, declines, and status updates. It should also show a simple screen where I can see the message flow and any errors or connection changes, so I can test the communication without real hardware.

Please organize it cleanly so the app logic, message handling, and any simple UI or views are separated in a sensible way. If you need current WebSocket or Python library details, look up the latest docs online. Include a straightforward way to run it locally and a few example flows or sample messages so I can verify it works quickly.