Firewall configuration. How to open a port on Linux?

When we install CentOS, the default configuration will be hardened and hence most of the unneeded ports will be blocked.
I configured Perforce proxy server in a centOS, which needed port 1666 to be opened. Since it is blocked, none of the other machines were able to contact perforce proxy server.  It used to give below error
$ p4 info

Perforce client error:
        Connect to server failed; check $P4PORT.
        TCP connect to xxx.xxx.com:1666 failed.
        connect: xxx.xxx..com:1666: WSAETIMEDOUT


To configure Firewall, we can use ipconfig command in Linux.
Here is the iptables command to open it
  iptables -t filter -A INPUT -p tcp --dport 1666 -j ACCEPT
where
   --table       -t table        table to manipulate (default: `filter')
   --append  -A chain            Append to chain
   --proto     -p proto        protocol: by number or name, eg. `tcp'
   --jump      -j target         target for rule (may load target extension)

Then save the configuration

   service iptables save

Next reload the configuration

  service iptables reload

Check the status

  service iptables status

O/P:

   Table: filter

   Chain INPUT (policy ACCEPT)

    num  target     prot opt source               destination

   1    ACCEPT     tcp  --  0.0.0.0/0            0.0.0.0/0           tcp dpt:1666

As shown above, now the port 1666 is opened.

Other options 

  iptables -L    

      where 

        --list    -L [chain [rulenum]]         List the rules in a chain or all chains

        --flush   -F [chain]          Delete all rules in  chain or all chains