运行一段VCL Reference中的示例代码出错，晕，何解？

Question

NMUDP帮助中，ReadStream方法的示例代码procedure TForm1.Button1Click(Sender: TObject);
var
  MyStream: TMemoryStream;
  C: String;
begin
  C := Edit1.Text;
  NMUDP1.RemoteHost := '127.0.0.1';
  NMUDP1.ReportLevel := Status_Basic;
  NMUDP1.RemotePort := 6668;
  MyStream := TMemoryStream.Create;
  try
    MyStream.Write(C[1], Length(C));
    NMUDP1.SendStream(MyStream);
  finally
    MyStream.Free;
  end;
end;procedure TForm1.NMUDP1DataReceived(Sender: TComponent; NumberBytes: Integer; FromIP: String; Port: Integer);
var
  C: String;
  MyStream: TMemoryStream;
begin
  MyStream := TMemoryStream.Create;
  try
    NMUDP1.ReadStream(MyStream);
    SetLength(C, NumberBytes);
    MyStream.Read(C[1], NumberBytes);
    Memo1.Lines.Add(C+': received '+IntToStr(NumberBytes)+' bytes from '+FromIP+' on port '+IntToStr(Port));
  finally
    MyStream.Free;
  end;
end;运行时
NMUDP1.ReadStream(MyStream);
此句上出现运行时异常 Stream Write Error 错

Answer 1

而且比较奇怪的，在上面一个的Stream的write中无错
而在下面的read反而出错了

Answer 2

经验不足,在Stream发送之前,先定位到开始位置,下面读的时候也一样
加入一句:MyStream.Seek(0,sobeginning);

Answer 3

修改后为:
procedure TForm1.Button1Click(Sender: TObject);
var
  MyStream: TMemoryStream;
  C: String;
begin
  C := Edit1.Text;
  NMUDP1.RemoteHost := '127.0.0.1';
  NMUDP1.ReportLevel := Status_Basic;
  NMUDP1.RemotePort := 6668;
  MyStream := TMemoryStream.Create;
  try
    MyStream.Write(C[1], Length(C));
    MyStream.Seek(0,soBeginning);
    NMUDP1.SendStream(MyStream);
  finally
    MyStream.Free;
  end;
end;procedure TForm1.NMUDP1DataReceived(Sender: TComponent; NumberBytes: Integer; FromIP: String; Port: Integer);
var
  C: String;
  MyStream: TMemoryStream;
begin
  MyStream := TMemoryStream.Create;
  try
    NMUDP1.ReadStream(MyStream);
    SetLength(C, NumberBytes);
    MyStream.Seek(0,soBeginning);
    MyStream.Read(C[1], NumberBytes);
    Memo1.Lines.Add(C+': received '+IntToStr(NumberBytes)+' bytes from '+FromIP+' on port '+IntToStr(Port));
  finally
    MyStream.Free;
  end;
end;