Due to the nature of a public account such as guestftp, preparing a file for transfer to the InterNet is a two stage process. Firstly, you need to transfer the file from your machine to uk.ac.nsf.sun, where it will be placed in a general area. You should then login to the guestftp service as usual and retrieve the file from this area.
For example, if you have a file foo.c on your local machine, transfer this using the remote filename foo.c, and remote username and password of guestftp.
Once this transfer has completed, login to the guestftp service, and the ret command to place the file in your directory on uk.ac.nsf.sun:
guest_ftp> ret Give name of file to be retrieved: foo.c Trying to retrieve now, result is..OK. guest_ftp> dir 26 Jun 19 17:07 foo.c total blocks: 400 guest_ftp>
The file is now ready to send to the US using the ftp command.