Rebuilding Protocols From Scratch Is the Fastest Path to Engineering Mastery

A software developer argues that truly understanding a system requires rebuilding it from the ground up, not just reading its documentation. Over his career, he reconstructed TCP, DNS, and the industrial Modbus protocol in C and Go, each time uncovering details that no library or lecture had revealed. Most recently, a colleague achieved a similar breakthrough by writing a small Go CLI that calls an LLM and executes its tools, finally grasping concepts like context windows and token counts. The author contends that rebuilding forces every edge case into the open, since the code either works or it fails. He presents this hands-on method as a practical way for developers to move from passive users of a technology to engineers who can debug, extend, and bend it to their needs.