Find out the open ports in an instance

 Below command will list out ports which are already defined in the linux machine:

$ semanage port -l | grep http_port_t

http_port_t                    tcp      80, 81, 443, 488, 8008, 8009, 8443, 9000
pegasus_http_port_t            tcp      5988

If you wish to add a new port to the list, run the below command:

$ semanage port -l | grep http_port_t -p tcp 7001

http_port_t                    tcp      7001, 80, 81, 443, 488, 8008, 8009, 8443, 9000
pegasus_http_port_t            tcp      5988

Check if firewall rules are enabled:

$ service iptables status

Table: filter
Chain INPUT (policy ACCEPT)
num  target     prot opt source               destination
1    DROP       tcp  --  0.0.0.0/0            0.0.0.0/0           tcp dpt:80
2    ACCEPT     tcp  --  0.0.0.0/0            0.0.0.0/0           tcp dpt:80
Chain FORWARD (policy ACCEPT)
num  target     prot opt source               destination
Chain OUTPUT (policy ACCEPT)
num  target     prot opt source               destination

If you wish to add specific port to firewall rules, run below command:

$ iptables -A INPUT -p tcp -m tcp --dport 7001 -j ACCEPT