Follow these steps to add a rule to iptables to allow incoming connections on port 9998:
Edit iptables:
# vi /etc/sysconfig/iptables
Find the following line in the file:
-A RH-Firewall-1-INPUT -j REJECT --reject-with icmp-host-prohibited
Add the following line BEFORE the above line:
-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 9998 -j ACCEPT
Restart iptables:
# service iptables restart
Other Port related articles:
Required Ports for the Uptime Infrastructure Monitor Monitoring Station
What ports need to be open to add an ESX or vCenter system to Uptime Infrastructure Monitor?
What ports are required for WMI agentless monitoring