This is a small script which will takecare of blocking and unblocking ports by asking user about his desire. Just copy this code to your system and change permissions and start executing it.

#!/bin/bash
#Author: Surendra Anne([email protected])

PATH=/usr/local/bin:/usr/bin:/bin:/usr/local/sbin:/usr/sbin:/sbin
clear
echo -e "############################nnnPresent ports opened on this machine are
$(iptables -nL INPUT | grep ACCEPT | grep dpt)
nCompleted listing...nnn#########################"
read -p "To open port enter open, to close etner close) " OPT1
if [[ "$OPT1" == open ]]
then
read -p "Please enter your desired port number to open: " PORT1
 if [[ "$PORT1" =~ [0-9]{1,6} ]]
 then
iptables -D INPUT $(iptables -nL INPUT --line-numbers | grep "$PORT1" | grep REJECT | awk '{print $1}')
 iptables -A INPUT -m tcp -p tcp --dport "$PORT1" -j ACCEPT && { service iptables save;service iptables restart; echo -e "Ports opend through iptables are n$(iptables -nL INPUT | grep ACCEPT | grep dpt)"; }
 else
 echo "Please enter a valid port(0-65000)"
 fi
elif [[ "$OPT1" == close ]]
then
read -p "Please enter your desired port number to close: " PORT1
        if [[ "$PORT1" =~ [0-9]{1,6} ]]
        then
 iptables -D INPUT $(iptables -nL INPUT --line-numbers | grep "$PORT1" | grep ACCEPT | awk '{print $1}')
        iptables -A INPUT -m tcp -p tcp --dport "$PORT1" -j REJECT && { service iptables save;service iptables restart; echo -e "Ports closed through iptables are n$(iptables -nL INPUT | grep REJECT | grep dpt)"; }
        else
        echo "Please enter a valid port(0-65000)"
        fi
else
echo "Please enter only open or close..! Exiting script now";exit 1
fi


Output: For closing a port

[[email protected] ~]# bash block-unblock-ports.sh 

############################


Present ports opened on this machine are
ACCEPT     tcp  --  0.0.0.0/0            0.0.0.0/0           state NEW tcp dpt:22 
ACCEPT     tcp  --  0.0.0.0/0            0.0.0.0/0           tcp dpt:80 

Completed listing...


#########################
To open port enter open, to close etner close) close
Please enter your desired port number to close: 80
iptables: Saving firewall rules to /etc/sysconfig/iptables:[  OK  ]
iptables: Flushing firewall rules:                         [  OK  ]
iptables: Setting chains to policy ACCEPT: filter          [  OK  ]
iptables: Unloading modules:                               [  OK  ]
iptables: Applying firewall rules:                         [  OK  ]
Ports closed through iptables are 
REJECT     tcp  --  0.0.0.0/0            0.0.0.0/0           tcp dpt:80 reject-with icmp-port-unreachable 

For opening port:

[[email protected] ~]# bash block-unblock-ports.sh 


############################


Present ports opened on this machine are
ACCEPT     tcp  --  0.0.0.0/0            0.0.0.0/0           state NEW tcp dpt:22 

Completed listing...


#########################
To open port enter open, to close etner close) open
Please enter your desired port number to open: 81
Bad argument `7'
Try `iptables -h' or 'iptables --help' for more information.
iptables: Saving firewall rules to /etc/sysconfig/iptables:[  OK  ]
iptables: Flushing firewall rules:                         [  OK  ]
iptables: Setting chains to policy ACCEPT: filter          [  OK  ]
iptables: Unloading modules:                               [  OK  ]
iptables: Applying firewall rules:                         [  OK  ]
Ports opend through iptables are 
ACCEPT     tcp  --  0.0.0.0/0            0.0.0.0/0           state NEW tcp dpt:22 
ACCEPT     tcp  --  0.0.0.0/0            0.0.0.0/0           tcp dpt:81 






Related concept:   Shell script/command to convert relative to Absolute path