You need to edit the greenfoot.defs file and specify the "proxy.host" and "proxy.port" settings, and add two (undocumented) settings: "proxy.username" and "proxy.password".
(This is from memory - try "proxy.user" if "proxy.username" doesn't seem to work).
Make sure "proxy.host" contains only the hostname, NOT the full URL of the host.
Hi, excellent - this works. For future reference it's "proxy.user" . So here's what I added:
proxy.host=ipaddress only here
proxy.port=port number here