(Delphi ActiveX) Cloudfare DNS over HTTPS

Cloudflare offers a DNS over HTTPS resolver at: https://cloudflare-dns.com/dns-query

This example demonstrates how to do a DNS lookup for a domain using Cloudfare's HTTPS resolver.

Chilkat for Delphi Downloads Chilkat ActiveX DLL for Delphi Chilkat non-ActiveX DLL for Delphi * The examples here use the ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Chilkat_TLB;

...

procedure TForm1.Button1Click(Sender: TObject);
var
http: TChilkatHttp;
url: WideString;
jsonResp: WideString;
json: TChilkatJsonObject;
Status: Integer;
TC: Integer;
RD: Integer;
RA: Integer;
AD: Integer;
CD: Integer;
i: Integer;
count_i: Integer;
name: WideString;
type: Integer;
TTL: Integer;
data: WideString;
ipAddr: WideString;

begin
// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

http := TChilkatHttp.Create(Self);

// Send the following CURL request:   curl -H 'accept: application/dns-json' 'https://cloudflare-dns.com/dns-query?name=chilkat.io&type=A'

http.Accept := 'application/dns-json';

url := 'https://cloudflare-dns.com/dns-query?name=chilkat.io&type=A';

jsonResp := http.QuickGetStr(url);
if (http.LastMethodSuccess <> 1) then
  begin
    Memo1.Lines.Add(http.LastErrorText);
    Exit;
  end;

Memo1.Lines.Add('Response Status Code: ' + IntToStr(http.LastStatus));

json := TChilkatJsonObject.Create(Self);
json.Load(jsonResp);
json.EmitCompact := 0;
Memo1.Lines.Add(json.Emit());

if (http.LastStatus <> 200) then
  begin
    Memo1.Lines.Add('Failed.');
    Exit;
  end;

// Sample output...
// (See the parsing code below..)
// 

// {
//   "Status": 0,
//   "TC": false,
//   "RD": true,
//   "RA": true,
//   "AD": false,
//   "CD": false,
//   "Question": [
//     {
//       "name": "chilkat.io.",
//       "type": 1
//     }
//   ],
//   "Answer": [
//     {
//       "name": "chilkat.io.",
//       "type": 1,
//       "TTL": 900,
//       "data": "52.25.83.238"
//     }
//   ]
// }

// Use this online tool to generate parsing code from sample JSON: 
// Generate Parsing Code from JSON

Status := json.IntOf('Status');
TC := json.BoolOf('TC');
RD := json.BoolOf('RD');
RA := json.BoolOf('RA');
AD := json.BoolOf('AD');
CD := json.BoolOf('CD');
i := 0;
count_i := json.SizeOfArray('Question');
while i < count_i do
  begin
    json.I := i;
    name := json.StringOf('Question[i].name');
    type := json.IntOf('Question[i].type');
    i := i + 1;
  end;

i := 0;
count_i := json.SizeOfArray('Answer');
// The domain name resolves to 1 or more IP addresses..
while i < count_i do
  begin
    json.I := i;
    name := json.StringOf('Answer[i].name');
    type := json.IntOf('Answer[i].type');
    TTL := json.IntOf('Answer[i].TTL');
    ipAddr := json.StringOf('Answer[i].data');

    Memo1.Lines.Add('IP Address: ' + ipAddr);
    i := i + 1;
  end;
end;