read UDP messages

unit Unit1;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, IdSocketHandle, IdBaseComponent,
  IdComponent, IdUDPBase, IdUDPServer, Vcl.StdCtrls;

type
  TForm1 = class(TForm)
    IdUDPServer1: TIdUDPServer;
    Memo1: TMemo;
    procedure FormCreate(Sender: TObject);
    procedure FormClose(Sender: TObject; var Action: TCloseAction);
    procedure IdUDPServer1UDPRead(AThread: TIdUDPListenerThread;
      AData: TBytes; ABinding: TIdSocketHandle);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;
  MyUDPMessage : String;

implementation

{$R *.dfm}

function BytesToString(bytearray: array of byte; len : Integer): String;
var
  a: Integer;
begin
  result := '';
  for a := 0 to len-1 do begin
    result := result + char(bytearray[a]);
  end;
end;

procedure TForm1.FormClose(Sender: TObject; var Action: TCloseAction);
begin
  Form1.IdUDPServer1.Active := False;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  Form1.IdUDPServer1.DefaultPort := 3333;
  Form1.IdUDPServer1.Active := True;
  Form1.IdUDPServer1.OnUDPRead := IdUDPServer1UDPRead;
end;

procedure TForm1.IdUDPServer1UDPRead(AThread: TIdUDPListenerThread;
  AData: TBytes; ABinding: TIdSocketHandle);
begin
   MyUDPMessage:=BytesToString(AData,10240);
   Memo1.Lines.Add(MyUDPMessage);
end;

end.