For most files, the preferred method is ssh-protected ftp from phobosmds.rhic.bnl.gov. (Note: The given link to the left no longer works on RCF if you follow it explicitly due to RCF security measures, but is kept for people's use elsewhere. Use the link to our explicit example instead.) Don't try to use rcf.rhic.bnl.gov. It can't see /phobos/dataxx according to RCF policy. Don't try to use rlnx03. It can't see the outside world. Ssh-protected ftp encrypts your password but transmits the file itself in clear text. It's a bit tricky the first few times you do it, but if you follow the instructions exactly it works.
For short files only, you can use scp to rftpexp.rcf.bnl.gov. Please do not use this for long files as this can really load down the systems. Don and Mark managed to bring RCF to its knees once by transfering gigabytes of data using scp between RCF and abacus. Short means ~10kb or less.
Click here for an explicit example showing how to transfer a file from (or to) RCF using ssh-protected ftp.