August 2025
Intermediate to advanced
272 pages
6h 14m
English
Content preview from Network Programming in Elixir and ErlangBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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Writing a Simple DNS Client
Let’s write a funky little Elixir client that works as a (small) subset of dig. Since our imagination knows no bounds, we’ll call it xdig. We’ve got our protocol code in XDig.Protocol from the previous section, so let’s focus on the network parts. All the code is in code/xdig.
The first thing we need is a DNS server to connect to. There are many to choose from, such as Google’s 8.8.8.8, but we’re going to use 1.1.1.1,[110] a neat alternative from the folks at CloudFlare and APNIC.
Our client needs to do the following:
- Open a UDP socket
- Build a DNS query message made of a header, one question, and zero answers
- Send the encoded message over UDP to the 1.1.1.1 DNS server
- Await a reply from the server
- Decode the reply
We’ll ...
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