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Learn · Networking

DNS, HTTP and other protocols

Seven lessons on the protocols programs speak: how DNS finds an address, the kinds of DNS record, URLs and HTTP, status codes and cookies, HTTPS and certificates, email, SSH and the common ports, and the tools for finding out what’s broken.

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How it works

Each lesson is a short read with examples, then a few practice questions. Some ask you to type an answer (a number, an address, what a piece of code prints), some have you pick one, and some have you tap steps or lines into the right order. You can try again as often as you like; after two misses there’s a button to show the answer.

What do I need to know first?

How networks work, so ports, TCP and UDP are familiar.

The other networking courses

Where is my progress saved? In this browser, like the rest of the site. Nothing to sign up for.

“Python” is a registered trademark of the Python Software Foundation. This course isn’t made by or affiliated with it.