[FTP/FTPS Only] Completes the asynchronous operation started in BeginInvokeFTPCommand.
The reply returned by the server.
Before calling BeginInvokeSiteCommand, you need to create a callback method that implements the AsyncCallback delegate. This callback method executes in a separate thread and is called by the system after BeginInvokeSiteCommand returns. The callback method must accept the IAsyncResult returned by the BeginInvokeSiteCommand method as a parameter. This parameter may then be passed to the EndInvokeSiteCommand method to complete the operation.