DNS Server in Go

This project implements a simple DNS server in Go, located in app/main.go. It listens for DNS queries over UDP and responds with a hardcoded answer for A record queries (IPv4 address for 127.0.0.1).

Features

• Listens on UDP port 2053 (127.0.0.1:2053)
• Parses DNS queries and constructs valid DNS responses
• Responds to A record (IPv4) queries with 127.0.0.1
• Handles basic DNS header fields and question/answer sections
• Ignores unsupported query types and classes

Getting Started

Prerequisites

• Go 1.24 or higher

Installation

Clone the repository:

git clone https://github.com/ronitrajfr/dns-server.git
cd dns-server

Running the Server

go run app/main.go

The server will start and listen for UDP DNS queries on 127.0.0.1:2053.

Testing the Server

You can test the server using dig:

dig @127.0.0.1 -p 2053 example.com A

You should receive a response with the IP address 127.0.0.1 for any A record query.

Code Overview

• app/main.go: Main server implementation. Handles UDP socket, parses DNS packets, and constructs responses.
• go.mod: Go module definition.

How It Works

• The server listens for UDP packets on 127.0.0.1:2053.
• For each incoming DNS query:
  • Parses the DNS header and question section.
  • If the query is for an A record (QTYPE=1, QCLASS=1), responds with 127.0.0.1.
  • For unsupported query types or classes, no response is sent.

Development

• Modify app/main.go to extend functionality (e.g., support more record types, logging, etc.).
• Use print statements for debugging; output will appear in the console.

License

This project is for educational purposes and is based on the Codecrafters DNS server challenge.