Delphi DLL

Check Internet Connectivity

See more Socket/SSL/TLS Examples

Demonstrates an efficient way to test for Internet connectivity. Delphi DLL

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

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Boolean;
socket: HCkSocket;
targetIp: PWideChar;
port: Integer;
ssl: Boolean;
timeoutMs: Integer;

begin
success := False;

socket := CkSocket_Create();
// 1. Use a reliable Anycast IP. 
//    8.8.8.8 (Google) or 1.1.1.1 (Cloudflare) are the industry standards.
targetIp := '8.8.8.8';

// 2. Use Port 53 (DNS). 
//    DNS servers typically listen on TCP Port 53 as well as UDP. 
//    (Alternatively, use port 443 if you suspect port 53 is blocked).
port := 53;

// 3. Disable SSL (0). 
//    We are not doing a handshake, just a TCP connection.
ssl := False;

// 4. Short Timeout (1500ms).
//    If you can't reach Google in 1.5 seconds, the connection is 
//    likely too poor for practical use anyway.
timeoutMs := 1500;

// Connect
success := CkSocket_Connect(socket,targetIp,port,ssl,timeoutMs);
if (success = False) then
  begin
    Memo1.Lines.Add(CkSocket__lastErrorText(socket));
    Exit;
  end;

CkSocket_Close(socket,10);

Memo1.Lines.Add('We have Internet connectivity.');

CkSocket_Dispose(socket);

end;