Internet connection

You can also use WinInet functions, here is a simple example

uses WinInet;

function IsConnected(const Url: string): Boolean;
var
  NetHandle: HINTERNET;
  UrlHandle: HINTERNET;
begin
  Result := False;
  NetHandle := InternetOpen('InetURL:/1.0', INTERNET_OPEN_TYPE_PRECONFIG, nil, nil, 0);

  if Assigned(NetHandle) then 
  begin
    UrlHandle := InternetOpenUrl(NetHandle, PChar(Url), nil, 0, INTERNET_FLAG_RELOAD, 0);

    if Assigned(UrlHandle) then
    begin
       Result := True;      
      InternetCloseHandle(UrlHandle);
    end;
    
    InternetCloseHandle(NetHandle);
  end;
end;

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IsConnected('http://www.microsoft.com')

ewangoya has given me a new approach.  I think I might use a mix of the two.  As an example, being connected to your local network would be proven by ewangoya's example.  Being able to reach the end point would be proven by mine.  Both could be useful.

Implement WININET.DLL and call function InternetGetConnectedState(..)

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private-Deklarationen }
  public
    { Public-Deklarationen }
  end;

  function InternetGetConnectedState(lpdwFlags: LPDWORD;dwReserved: DWORD): BOOL; stdcall; external 'WININET.DLL';

var
  Form1: TForm1;

implementation
{$R *.dfm}

uses WinInet;

const
  INET_CONN_MODEM = 1;
  INET_CONN_LAN = 2;
  INET_CONN_PROXY = 4;
  INET_CONN_MODEM_BUSY = 8;


function IsConnectedToInternet: Boolean;
var
  INetConnectionTypes: Integer;
begin
  try
    INetConnectionTypes := INET_CONN_MODEM + INET_CONN_LAN + INET_CONN_PROXY;
    Result:= InternetGetConnectedState(@INetConnectionTypes, 0);
  except
    Result := false;
  end;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  If IsConnectedToInternet Then
    ShowMessage('Connected to Internet!!!')
  Else
    ShowMessage('NOT connected to Internet!!!');
end;

end.

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