delphi7自带indy的udp控件问题

Question

收发一段字符串
客户端：
procedure TForm1.Button1Click(Sender: TObject);
var str:string;
begin
  str:=Edit1.Text;
  IdUDPClient1.SendBuffer(str,length(str));
end;
服务端：OnUDPRead事件
procedure TForm1.IdUDPServer1UDPRead(Sender: TObject; AData: TStream;
  ABinding: TIdSocketHandle);
var str:string;
begin
  AData.ReadBuffer(str,AData.Size);//跟踪发现，事件能响应，但str总是没数据
  ListBox1.Items.Add(str);
end;点发送，接收总是报错，请教高手，原因

Answer 1

//针对楼主的要求简单写了一个
unit Unit1;interfaceuses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, IdUDPClient, IdBaseComponent, IdComponent, IdUDPBase,
  IdUDPServer, StdCtrls, IdSocketHandle;type
  TForm1 = class(TForm)
    IdUDPServer1: TIdUDPServer;
    IdUDPClient1: TIdUDPClient;
    cmdSend: TButton;
    Edit1: TEdit;
    procedure FormCreate(Sender: TObject);
    procedure cmdSendClick(Sender: TObject);
    procedure IdUDPServer1UDPRead(Sender: TObject; AData: TStream;
      ABinding: TIdSocketHandle);
  private
    { Private declarations }
  public
    { Public declarations }
  end;var
  Form1: TForm1;implementation{$R *.dfm}procedure TForm1.FormCreate(Sender: TObject);
begin
self.IdUDPServer1.DefaultPort:=22222;
self.IdUDPServer1.Active:=true;
end;procedure TForm1.cmdSendClick(Sender: TObject);
var
  s:string;
begin
  s:=edit1.Text;
  self.IdUDPClient1.SendBuffer('127.0.0.1',22222,s[1],length(s));
end;procedure TForm1.IdUDPServer1UDPRead(Sender: TObject; AData: TStream;
  ABinding: TIdSocketHandle);
var
  strStream:TStringStream;
begin
  strStream:= TStringStream.Create( '' );
  try
    strStream.CopyFrom( AData, AData.Size );
    ms.Position:=0;
    showmessage( strStream.DataString );
  finally
    strStream.Free;
  end;
end;end.