Error in send file over FTP node

Hey,

wanted to ask for some help with send file over FTP node.

I've configured this node exacly same as retrieve file via FTP - external system key, server hostname, server port + remote directory path i entered "Appian_Attachments_TST" (i tried many configurations for this field with some / or \ or c:\ but problems still remains) and mainly gives me this error

Stream handler unavailable due to: For input string: "21Appian_Attachments_TST"

or

when i put empty it does return @serverhostname

I can't figure it out by myself what am i doing wrong with this node everything supposed to be fine :( 
This is very important for me because r'm running out of time

Hope someone knows how to deal with this problem 

thank you in advance 

David