---
title: "How TCP Handshake Works"
url: https://daily.dev/posts/how-tcp-handshake-works-hm2jha6hw
source_url: https://newsletter.systemdesigncodex.com/p/how-tcp-handshake-works
type: article
source: "System Design Codex"
published: 2026-03-31T08:29:33.109Z
updated: 2026-03-31T08:29:51.749Z
tags: ["networking"]
reading_time: 3
upvotes: 13
comments: 2
language: en
---

> ## Documentation Index
> Fetch the complete documentation index at: https://daily.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# How TCP Handshake Works

**[System Design Codex](https://daily.dev/sources/systemdesigncodex)** · 3 min read · 13 upvotes · 2 comments

## Summary

A beginner-friendly walkthrough of the TCP 3-way handshake, covering each step: SYN, SYN-ACK, and ACK. Explains the role of control flags and initial sequence numbers (ISNs), why ISNs are randomized for security, and briefly touches on whether the internet is moving away from TCP toward QUIC with HTTP/3.

## Full article

daily.dev links to this article rather than hosting it. Read it at the original source: <https://newsletter.systemdesigncodex.com/p/how-tcp-handshake-works>

## Community discussion

Top comments from developers on daily.dev.

**@oxg0df4th3r** · 1 upvotes

> The article was helpful

**@bobbyiliev** · 0 upvotes

> this is quite helpful! also this one here might be interesting as it helps visualize both udp and tcp: [https://app.daily.dev/posts/wJDJpvyFc](https://app.daily.dev/posts/wJDJpvyFc)

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- [The Internet is Cool. Thank you, TCP](https://daily.dev/posts/the-internet-is-cool-thank-you-tcp-3boxuwpqz) · Hacker News · 1 upvotes · 0 comments

---

Tags: [#networking](https://daily.dev/tags/networking)

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