Backend development

Stage 1 · Lesson 8 of 10

TCP connections and TLS

Your language and how HTTP works

Once the client knows your server's , it opens a connection to a port, usually 443. TCP delivers bytes in order and resends any that get lost on the way. Setting it up takes a short three-way greeting called the (SYN, SYN-ACK, ACK).

TLS then runs on top of TCP, and it is what puts the S in HTTPS. The server shows a that proves it owns the domain. Both sides agree on secret keys, and from then on everything is encrypted, and any tampering is detected.

TLS 1.3 needs one for this. Every handshake adds waiting time (latency). That is why clients reuse connections, and why opening a new connection for every request is slow.

Common trapthinking HTTPS hides everything: the server's IP address, and usually its hostname, are still visible on the network.

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Resources for this stage

Start with· follow one of these

  • CoursePaid
    Grokking JavaScript Fundamentals

    Design Gurus · Beginner · $50

    JavaScript itself in a sensible order: scope, closures, promises and async code

  • GuideFree
    Node.js Learn

    OpenJS Foundation · Beginner

    Official guides on the event loop, async work, the http module and environment variables

Practise

  • Exercism

    Your language track: small exercises with free mentor feedback on idiomatic code

Keep handy

  • The TypeScript Handbook

    Read Everyday Types and Narrowing first, then keep it open while you write TypeScript

  • MDN Web Docs

    Read the HTTP overview, methods, headers and status code pages until they feel obvious

Also worth your time

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