Why Put a Web Server Inside a Phone?

When I was building Background Camera RemoteStream — an Android app that records video with the screen off — I needed a way for users to control the camera remotely. The phone's screen is off, so you can't tap anything. The solution: embed a web server inside the app and let users control it from any browser on the same WiFi.

This turned out to be one of the most interesting technical challenges in the whole project. Here's how it works.

Choosing Ktor

I evaluated several options for an embedded HTTP server on Android:

NanoHTTPD — Lightweight and popular, but limited. No WebSocket support out of the box, no coroutine integration, and the API feels dated.

Ktor — JetBrains' async HTTP framework.…