DevOps and cloud

Stage 2 · Lesson 2 of 8

TCP, UDP and ports

Networking for engineers

IP gets a to the right machine. and UDP then get it to the right program on that machine, which is identified by a port number. TCP first sets up a connection with a three-way handshake, a quick hello in three messages.

It then delivers data reliably and in order. , SSH and databases all use TCP. UDP just sends small packets with no promise that they arrive, or arrive in order.

That suits DNS lookups, video calls and , the transport under HTTP/3. Know the common ports: 22 for SSH, 53 for DNS, 80 and 443 for HTTP and HTTPS, and 5432 for . A service is reachable only if it listens on the right address and port, and nothing in between blocks it.

Common trapan app bound to 127.0.0.1, which works on the server itself but refuses every connection from outside.

A question to check yourself, an AI practice session and 1 cheat sheet entry come with the full roadmap. Unlock

Resources for this stage

Start with

Practise

  • DevOps Exercises

    Answer its networking questions before reading the answers to find your gaps

Keep handy

  • NGINX Beginner's Guide

    Official guide to serving files and proxying to an app, the base of every config

  • MDN Web Docs

    The HTTP guides on headers, caching and status codes, for debugging proxies

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