You've got quite a few options to select from here, the main thing to think about is your security requirements and data integrity (ie, is it ok to have a partial file etc?).
Once you know what you need from that, it should be easy to pick what you want to use.
As for mechanisms to transfer your files, here's a few ideas that might work for you:
- samba: Run smbd on your three unix servers then map drives on the windows server to these shares. This will mean you don't actually need to store the files over on the windows server, you can read them over the network. Hard to get more up-to-date than that
- ftp push: Run an ftpd on the windows server and have the unix servers push files over via ftp. Use send/expect to interact with ftp or use curl to do the transfer on the commandline.
- ssh/scp: Run an sshd (eg cygwin) on your windows server so that you can automate file pushes from the unix servers. This will give you encrypted transfers and allow you to use ssh keys - that way you don't need to store a password on each of the servers.
- email: Run an smtpd on the windows server and have it trigger your log application (or just a copy) on incomming emails for a certain address. Then on each unix server, uuencode/mpack/embed the logs to your email and fire them off.
- Third party file transfer tools like connect direct or xcom: Most of these give you protection from trying to use partial files etc and have clients and servers for many different platforms. These generally cost money to use though :/
If you need encryption, then it's ssh, sftp, email combined with pgp, or the thrid party tools for you.
If you need passwordless connection, you can script pretty much anything but will have to store the password in the script (generally a bad thing) unless you go with samba, ssh, email, or the right thrid party tool.
If it's important that your windows app doesn't try to use a file that's only half copied, the only (fairly) sure solution is to script the use of a temp file that gets renamed after it's fully sent, use email, or a thirld party tool.
Hope that helps, sing out if you want further elaboration on a particular solution.