Short answer: you can't. Ports below 1024 can be opened only by root. As per comment - well, you can, using CAP_NET_BIND_SERVICE, but that approach, applied to java bin will make any java program to be run with this setting, which is undesirable, if not a security risk.
The long answer: you can redirect connections on port 80 to some other port you can open as normal user.
Run as root:
# iptables -t nat -A PREROUTING -p tcp --dport 80 -j REDIRECT --to-port 8080
As loopback devices (like localhost) do not use the prerouting rules, if you need to use localhost, etc., add this rule as well (thanks @Francesco):
# iptables -t nat -I OUTPUT -p tcp -d 127.0.0.1 --dport 80 -j REDIRECT --to-ports 8080
NOTE: The above solution is not well suited for multi-user systems, as any user can open port 8080 (or any other high port you decide to use), thus intercepting the traffic. (Credits to CesarB).
EDIT: as per comment question - to delete the above rule:
# iptables -t nat --line-numbers -n -L
This will output something like:
Chain PREROUTING (policy ACCEPT)
num target prot opt source destination
1 REDIRECT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:8080 redir ports 8088
2 REDIRECT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:80 redir ports 8080
The rule you are interested in is nr. 2, so to delete it:
# iptables -t nat -D PREROUTING 2
If you check the official specification of the File Transfer
Protocol, you'll find that:
FTP can be run in active mode or
passive mode, which control how the
second connection is opened. In active
mode the client sends the server the
IP address port number that the client
will use for the data connection, and
the server opens the connection.
Passive mode was devised for use where
the client is behind a firewall and
unable to accept incoming TCP
connections. The server sends the
client an IP address and port number
and the client opens the connection to
the server. Both modes were updated in
September 1998 to add support for IPv6
and made some other changes to passive
mode, making it extended passive mode.
So, my first thought is that there's something wrong with your folder permissions. Double check them.
Best Answer
Once you have logged into the site with FTP, type
passive
and then do your transfer.