Port translation

[Uno Engborg]

For various reasons I would like to  forward trafic to port 390 to port 
5432 on the same host. One would think this would be a
simple task for iptables but I have now tinkered with this for two days, 
and I still fail to get it right.

I try something like:
echo 1 > /proc/sys/net/ipv4/ip_forward

iptables -t nat -A PREROUTING  -p tcp  --dport 390 -j REDIRECT 
--to-ports 5432

I have also tried :
iptables -t nat -A PREROUTING  -p tcp --dport 390 -j DNAT --to 
192.168.0.5:5432

where 192.168.0.5 is the address of the host


Any ideas on how to do this?

Regards
Uno Engborg