How Android works
Connectivity, location & sensors
Radios, sockets, satellites and a chip that tells you which way is down.
5 pages58 min5 interactive7800 words
- 01The networking stackAndroid does not just have a TCP stack. It has a policy engine in front of one: per-app routing, a per-UID firewall, a DNS resolver that can be encrypted, and a rule that plain HTTP is refused by default.intermediate13 mininteractive
- 02Wi-Fi, Bluetooth and NFCThree radios, one pattern: a framework service, a vendor HAL, and a Mainline module trying to keep the whole thing updatable. What differs is the permission story — and it changed completely in Android 12.intermediate11 mininteractive
- 03TelephonyThe radio is the most vendor-specific part of Android, and the RIL is the seam that tries to hide it. It is also the area where the platform's default-app rules and the law intersect.intermediate11 mininteractive
- 04LocationAndroid's location stack has two APIs, three signal sources and four permission states. The history of those permissions is the clearest example of the platform learning to ask better questions.intermediate12 mininteractive
- 05SensorsA phone has a dozen tiny instruments sampling continuously. The interesting engineering is not reading them — it is fanning one hardware stream out to every app without waking the processor for each sample.intermediate11 mininteractive
Test yourself
Test yourself: Connectivity, location & sensors
Why is telephony described as the most vendor-specific area of Android?