Doing DNS SRV lookups in Ruby using stdlib in 2.3.0

README.md

DNS SRV Lookups in Ruby

Prerequisites

• Nix 1.11+ OR Ruby 2.3.x

If using Nix you can just load the environment with nix-shell shell.nix.

Now we can test an entry via command-line using host or dig commands:

[nix-shell:~/src/github/mbbx6spp/ruby-dns-examples]$ host -tSRV _http._tcp.referentiallabs.rocks
_http._tcp.referentiallabs.rocks has SRV record 10 50 80 fake0.referentiallabs.rocks.
_http._tcp.referentiallabs.rocks has SRV record 10 50 80 fake1.referentiallabs.rocks.

Look at the code in srvexample0.rb for Ruby code, and you can run it like so here:

[nix-shell:~/src/github/mbbx6spp/ruby-dns-examples]$ ruby srvexample0.rb
_http._tcp.referentiallabs.rocks has SRV record 10 50 80 fake1.referentiallabs.rocks.
_http._tcp.referentiallabs.rocks has SRV record 10 50 80 fake0.referentiallabs.rocks.

Cheers.

shell.nix

{ pkgs ? import <nixpkgs> {}
, ... }:
let
  inherit (pkgs) runCommand ruby;
in runCommand "dummy" {
  buildInputs = [
    ruby
  ];
} ""

srvexample0.rb

require 'resolv'

class Resolv::DNS::Resource::IN::SRV
  def to_s
    "SRV #{priority} #{weight} #{target} #{port}"
  end
end

opts = { nameserver: ['8.8.4.4', '8.8.8.8'] }
domain = "referentiallabs.rocks"
resolver = Resolv::DNS.new(opts)
puts resolver.getresource("_http._tcp.#{domain}", Resolv::DNS::Resource::IN::SRV).to_s