I have used iptables and opened a port
vi /etc/sysconfig/iptables
-A RH-Firewall-1-INPUT -p tcp -m state --state NEW -m tcp --dport 1500 -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp -m state --state NEW -m tcp --dport 1505 -j ACCEPT
-A RH-Firewall-1-INPUT -p udp -m state --state NEW -m udp --dport 1500 -j ACCEPT
-A RH-Firewall-1-INPUT -p udp -m state --state NEW -m udp --dport 1505 -j ACCEPT

saved the file and did service iptables restart
However nmap and netstat are not showing the port open.
netstat -tanp | grep LISTEN

All searching I have done have shown this is the way to do it.

An ideas would be appreciated.
Thanks,

I am using Red Hat Enterprise Linux ES release 4 (Nahant Update 5)

There is a difference between allowing traffic on a port, and actually running a service that LISTENS on that port. You can open port 1500 all you'd like...but if there's no service actually present on that port, it won't show anything. What service did you configure to use port 1500? Have you verified it's running?
RHEL4 is VERY old...and, since you're using RHEL, have you contacted Red Hat support yet?? You are paying for RHEL, right???

Can you provide any links how to set up a service to listen on a port?
I know it is old it will be updated next year.

Thanks

No, that's like asking "How high is up??" Each service is configured differently...you have to decide what service you want to run, then read up on how to configure it.
At which point it'll be even OLDER, and more unstable. If you're not paying for RHEL, then load CentOS...it's 99.x% identical, but FREE.

The issue is budget and downtime. We are paying for RHEL. The problem is getting the new servers approved. Running the newest RHEL on and old hunk of junk would not make much more sense. Plus the upgrade of the 3rd party software requires 10 hours downtime on a 24x7 machine.

Sorry, but that doesn't make much sense to me, no matter how you look at it.

If the machine is that critical to your business, you should have it up to date with a backup system for it. If you DON'T have those things, then the server isn't critical at all, and 10 hours of downtime shouldn't matter...especially after hours.

If the server is critical, it should be trivial to purchase a new server (for about $1000 or less), and load the latest RHEL on it. Since you are paying for RHEL, your license can be migrated over at very little/no cost. Get the new 3rd party software up and running, migrate data, test it, and move forward. If the server/software is THAT critical, it's insane not to have a working backup server to fail over to, especially one that's running old OS and (ostensibly), an old version of the 3rd party software.

And again, if you are paying for RHEL, you can call Red Hat support for questions about services.