Delphi IdTCPClient.connect Hanging while threaded - delphi

Question

I am trying to run 8 threads making IdTCPClient repeatedly scanning a range of IP. When these threads are running, the main form is hanging, lagging. The "IdTCClient.connect" is the issue. Is there a way to fix that ?
unit Unit3;
interface
uses
Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls;
type
TTcpThread = class(TThread)
Idx: word;
procedure Execute; override;
end;
TForm3 = class(TForm)
procedure FormShow(Sender: TObject);
private
public
end;
var
Form3: TForm3;
implementation
uses IdTCPClient;
{$R *.dfm}
procedure TTcpThread.Execute;
begin
for var i := Idx*8 to (Idx*8) + (8-1) do // 8 IP per Thread
begin
var TCP := TidTCPClient.Create(nil);
TCP.Host := '192.168.1.' + i.ToString;;
TCP.Port := 9999;
TCP.ConnectTimeout := 500;
TCP.ReadTimeout := 1000;
try
TCP.Connect;
TCP.Disconnect;
except end;
TCP.Free;
end;
end;
procedure TForm3.FormShow(Sender: TObject);
begin
for var i := 0 to 32-1 do // 32 Threads
begin
var Thread := TTcpThread.Create(True);
Thread.Idx := i;
Thread.FreeOnTerminate := True;
Thread.Start;
end;
end;
end.
The mainform will freeze/lag while the threads are running