Although my field of interest is quite diverse that I don't come up with the primary field, I enjoy implementing protocols on papers or specifications. One of my recent work is an implementation of TCP Simultaneous Open, where you can establish TCP connection without having the conventional three-way handshake. I've also written SHA-256 in TypeScript, and have been working on implementing Media over QUIC Transport, a live streaming protocol on HTTP/3.
I also write web apps for fun and research purpose sometimes. As I like tinkering network connection on an application layer WebRTC, WebSocket and WebTransport are what I usually code with (e.g. Instant Drop).