Simple Indy Server doesn't receive in order

I have a simple idTCPClient and idTCPServer but messages aren't received in
order...

Client:
Var
  _Client: TIdTCPClient;

class procedure TSimpleClass.Send(S: String);
begin
  Try
    _Client.Connect;
    _Client.IOHandler.WriteLn(S);
  Finally
    _Client.Disconnect;
  End;
end;

Initialization
  _Client := TIdTCPClient.Create(nil);
  _Client.Host := '127.0.0.1';
  _Client.Port := 6000;

Finalization
  _Client.Free;

Server:
procedure TForm1.IdTCPServer1Execute(AContext: TIdContext);
Var
    S: String;
begin
   S  := Acontext.Connection.IOHandler.ReadLn;
   Memo1.Lines.Add( S);
end;

What am I doing wrong?? How can I fix this?

Thanks, Rael