Sync List with FTP fails due to closed connection

I'm trying to use the doc sync control in Sharepoint.  I have it installed and the options show up in the Sharepoint ribbon.

I select a file and click on "sync list with ftp"

I fill out the form using the options that I know work in Filezilla

However, the Aspose control fails everytime with the response:
Unable to send items Reason: Fail to send command:Unable to write data to the transport connection: An existing connection was forcibly closed by the remote host.

Is this a problem with my sharepoint server, the remote server I'm ftp'ing the files to, or the Aspose control itself?

Any ideas how to fix this?