Delphi DLL

Cloudfare DNS over HTTPS

See more Cloudfare Examples

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.

Delphi DLL

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

...

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

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

http := CkHttp_Create();

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

CkHttp_putAccept(http,'application/dns-json');

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

jsonResp := CkHttp__quickGetStr(http,url);
if (CkHttp_getLastMethodSuccess(http) <> True) then
  begin
    Memo1.Lines.Add(CkHttp__lastErrorText(http));
    Exit;
  end;

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

json := CkJsonObject_Create();
CkJsonObject_Load(json,jsonResp);
CkJsonObject_putEmitCompact(json,False);
Memo1.Lines.Add(CkJsonObject__emit(json));

if (CkHttp_getLastStatus(http) <> 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 := CkJsonObject_IntOf(json,'Status');
TC := CkJsonObject_BoolOf(json,'TC');
RD := CkJsonObject_BoolOf(json,'RD');
RA := CkJsonObject_BoolOf(json,'RA');
AD := CkJsonObject_BoolOf(json,'AD');
CD := CkJsonObject_BoolOf(json,'CD');
i := 0;
count_i := CkJsonObject_SizeOfArray(json,'Question');
while i < count_i do
  begin
    CkJsonObject_putI(json,i);
    name := CkJsonObject__stringOf(json,'Question[i].name');
    type := CkJsonObject_IntOf(json,'Question[i].type');
    i := i + 1;
  end;

i := 0;
count_i := CkJsonObject_SizeOfArray(json,'Answer');
// The domain name resolves to 1 or more IP addresses..
while i < count_i do
  begin
    CkJsonObject_putI(json,i);
    name := CkJsonObject__stringOf(json,'Answer[i].name');
    type := CkJsonObject_IntOf(json,'Answer[i].type');
    TTL := CkJsonObject_IntOf(json,'Answer[i].TTL');
    ipAddr := CkJsonObject__stringOf(json,'Answer[i].data');

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

CkHttp_Dispose(http);
CkJsonObject_Dispose(json);

end;