[FTP/FTPS Only] Completes the asynchronous operation started in BeginInvokeFTPCommand.
The reply returned by the server.
Before calling BeginInvokeFTPCommand, 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 BeginInvokeFTPCommand returns. The callback method must accept the IAsyncResult returned by the BeginInvokeFTPCommand method as a parameter. This parameter may then be passed to the EndInvokeFTPCommand method to complete the operation.