Delphi DLL

Bind and Listen on a Randomly Selected Unused Port

See more Socket/SSL/TLS Examples

Demonstrates how to bind and listen on a randomly selected unused port.

Note:The ListenPort property used in this example is available starting in Chilkat v9.5.0.59.

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;
listenSocket: HCkSocket;
listenPort: Integer;

begin
success := False;

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

listenSocket := CkSocket_Create();

// Pass a value of 0 for the port number to randomly select
// an unused port.
// (The 2nd argument allows for a backlog of 25 pending connection requests when accepting connections.)
success := CkSocket_BindAndListen(listenSocket,5555,25);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkSocket__lastErrorText(listenSocket));
    Exit;
  end;

// Find out what port was chosen.
// Note: The ListenPort propety was added in Chilkat v9.5.0.59
listenPort := CkSocket_getListenPort(listenSocket);
Memo1.Lines.Add('Chosen listen port = ' + IntToStr(listenPort));

CkSocket_Dispose(listenSocket);

end;