What really happens when a “cloud-only” smart switch quietly listens on your local network?

This book is a hands-on reverse-engineering journey into the SONOFF Smart Switch R4, uncovering how eWeLink devices communicate beyond the app and the cloud. Starting from a simple home Wi-Fi setup, the story walks you through network discovery, hidden LAN endpoints, encrypted payloads, and a carefully executed man-in-the-middle attack that reveals a fully functional local control interface—no firmware flashing, no brute force, no guesswork.

You’ll see why Wireshark initially shows nothing, how HTTPS interception exposes zeroconf APIs, and why the device key—not the API key—unlocks AES-128-CBC encryption. What begins as unreadable traffic transforms into clear, actionable JSON commands that control the relay instantly and locally.

Written as a technical detective story, this book explains not only how it works, but why it was designed this way—and how such systems can be secured better. If you enjoy IoT, security, or understanding what your smart devices are really doing on your network, this is a journey worth taking.