How the Internet Actually Works
Every web application you've built relies on the internet — and the vast majority of vibe coders couldn't tell you what happens between the moment you call fetch() and the moment you get a response. TCP handshakes, DNS resolution, TLS negotiation, HTTP framing — these aren't irrelevant implementation details. They're the plumbing that determines whether your app is fast or slow, secure or vulnerable, reliable or flaky. This module takes you through the full network stack, from the physical layer up to HTTP. You'll understand why three messages are exchanged before any data is sent (the TCP handshake), how a domain name becomes an IP address (DNS), what TLS actually does to make HTTPS secure, and why HTTP/2 and HTTP/3 were invented to fix the performance problems of HTTP/1.1. You'll also learn about WebSockets for real-time communication and how CDNs work to serve your content faster. The project — building an HTTP server from scratch using raw TCP sockets — makes all of this concrete. When you've implemented request parsing, header handling, and response generation yourself, you'll never look at an Express route handler the same way again. You'll understand exactly what Express is doing for you, and you'll be equipped to reason about performance, debugging, and security in a way that vibe coders simply can't.
What You'll Learn
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1
The Network Stack — Physical to Application layer
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2
TCP/IP Deep Dive — Three-way handshake, flow control, congestion
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3
HTTP/HTTPS — Methods, headers, status codes, TLS
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4
DNS — How names become addresses
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5
WebSockets, gRPC, and Beyond HTTP — Real-time and efficient protocols
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6
CDNs and Edge Computing — Bringing data close to users
Capstone Project: Build an HTTP Server from Scratch
Implement a working HTTP/1.1 server using only raw TCP sockets — handling request parsing, header validation, routing, static file serving, and correct status code responses without using any HTTP framework. You'll add support for persistent connections (keep-alive), chunked transfer encoding, and CORS headers, gaining a deep understanding of what frameworks like Express handle automatically and why those abstractions exist.
Why This Matters for Your Career
Networking knowledge transforms your debugging capabilities. When a request is slow, you need to know whether the latency is in DNS resolution, TCP setup, TLS negotiation, server processing time, or data transfer — and you need to read a network waterfall to tell. When a security vulnerability is reported in your TLS configuration, you need to understand what TLS actually provides and what a downgrade attack looks like. HTTP is the protocol your entire career runs on. Every API you call, every webhook you receive, every authentication flow you implement uses HTTP. Understanding it at the protocol level — not just the framework abstraction — means you can debug curl vs browser behavior differences, understand CORS at a mechanical level rather than just copying headers, and design APIs that use HTTP semantics correctly. As applications move toward edge computing, real-time communication, and binary protocols like gRPC, engineers who understand the full networking stack are equipped to evaluate and use these technologies effectively. The engineers who stay relevant as the infrastructure evolves are those who understand the fundamentals beneath the frameworks.