Android-Controlled Bluetooth Double-Bell Alarm Clock

What is it? Doorbot is an Internet-connected door unlocker that I built for a community space. It allows people to enter the space without needing to be buzzed in. System Architecture The Doorbot system consists of: servo motors to actuate the door buzzer button ESP8266 microcontroller with built-in Wi-Fi NodeMCU firmware for ESP8266 lua...

This post is a short overview of what is required for a minimal, download-only BitTorrent implementation. Earlier this year, I wrote a BitTorrent client as an excuse to practice concurrency and networking concepts. But the resources and documentation I found while researching the protocol felt scattered, so I’m distilling my understanding here as...

A conversation with a coworker turned me on to the fact that a surprising range of operations in Python are atomic, even operations like dictionary and class member assignment. This wasn’t something I would have anticipated, given the number of machine language instructions that must ultimately be performed to complete an operation like hash...

Earlier this year, I read The Architecture of Open Source Applications, Volume II: Structure, Scale, and a Few More Fearless Hacks. It was an excellent read, and fills a gap in the market for software engineering books: Architects look at thousands of buildings during their training, and study critiques of those buildings written by masters. In...

While re-reading The Architecture of Open Source Applications, Volume II, a line in the chapter on git caught my eye: if two objects are different they will have different SHAs. This was surprising, as there should always be be some very very small but nonzero chance of a hash collision. Either the book is simplifying for ease of explanation,...