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Why Names Exist

Lesson 5 of 47 in Coddy's Networking with the Terminal course.

You have an address to send a request to. So why does anyone type example.com instead of 93.184.216.34?

Two reasons. Addresses are hard to remember, and worse, they change. A site moves to a new host, adds a second server, or switches provider, and the address changes while the name stays exactly the same.

DNS, the Domain Name System, is the phone book that turns a name into an address at the moment you need it. It is a lookup service running quietly behind almost every request you make.

That means every request really has two steps: resolve the name into an address, then connect to that address. Keep them apart in your head, because when something fails, working out which of the two broke is most of the diagnosis. A name that will not resolve never got as far as connecting.

Challenge

Medium

Show that a name is just a stand-in for an address.

Create index.html containing exactly SAME
Serve the folder on port 9103 in the background
Fetch it twice: once using 127.0.0.1 and once using localhost

Both requests reach the same server, so the output is:

SAME
SAME

Try it yourself

Terminal

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Networking with the Terminal

1How Networks Talk

What Is a Network Clients and Servers IP Addresses Your First Request

4Is It Reachable?

ICMP and ping Reading Ping Output When Ping Lies Refused or Timed Out Recap: Reachability

7Sending Data

POST with -d What -d Actually Sends Form Encoding Sending JSON PUT and DELETE Recap: Writing Data

2Names and DNS

Why Names ExistThe Hosts File Looking Up a Name Record Types Recap: Names

5HTTP by Hand

Anatomy of a Request Request Methods Status Codes Response Headers Writing a Response Recap: HTTP Basics

8HTTPS and TLS

Why HTTPS The Scheme Picks the Port Certificates and Trust When TLS Fails Recap: HTTPS

3Ports and Sockets

What Is a Port Well-Known Ports Localhost Listening vs Connecting Recap: Ports

6curl in Depth

Seeing the Headers Saving Responses Custom Headers Status and Timing curl Exit Codes Recap: curl Flags

9Auth and Debugging

API Keys and Bearer The User Agent Timeouts and Retries Reading a Failure Recap: Debugging

Practice on your own: Terminal playground