Trivia¶

A Field Guide to the Numbers that Show Up Everywhere

I used to see the same numbers popping up in error logs, hex dumps, and config files.

255, 1024, 65535, 2147483647.

They felt like a secret code. If you know these numbers, you can start to guess what kind of bug you're looking at before you even read the code.

Let's look at the "Magic Numbers" of computing and why they keep appearing.

Why is 127.0.0.1 the 'Loopback' Address?

If you've ever built a website or run a database, you've used 127.0.0.1. It’s the universal address for "this computer right here."

But have you ever stopped to wonder why it's such a weird number? Why not 1.1.1.1 or 0.0.0.0? And why is the whole 127.x.x.x block reserved just for us?