var
  ServerSocket1: TServerSocket;    procedure TForm1.Button1Click(Sender: TObject);
begin
  if not Assigned(ServerSocket1) then
    ServerSocket1 := TServerSocket.Create(nil);
  // ...
  ServerSocket1.Active := True;
end;    procedure TForm1.Button2Click(Sender: TObject);
begin
  if Assigned(ServerSocket1) then
    FreeAndNil(ServerSocket1);
end;