Issue while Uploading files

Hi,
 
I am working on a utility using the w3c libraries. I am using this to
download files from the site an FTP or HTTP server . The utility works
fine when I am trying to FTP or HTTP file, if the Client and the Server
machine are having the same OS, but when I try across OS it fails ( I
mean when I have a Windows Client and a Linux Server or Vice Versa the
utility fails to transfer files )
 
Can any one suggest me what the probable reason could be, so that I can
resolve these issues.
 
Thanks in Advance.
Deepak.

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