If you are not allowed to run a service on the server, then you'll have to depend on a service already on the server. Can you run FTP? RCP? SFTP? SCP? Can you mount the server's disk? Can you access files via http? etc.
Furthermore, there may not be a
java api either? Once you figure out how to do it, you may have write a script that does it, and call the script from your program.
Henry