Check if a port is blocked or allowed using iptables – the better way

Use the following linux command as root user to check if a port is blocked on your machine or not.

Copy the command. Replace <PORT> with actual port number e.g. 22 and run it on bash terminal.

for tcp ports :

#start

port=<PORT>; (iptables -nL INPUT | head -1 | grep "DROP" > /dev/null || \
( echo -e "\nPort $port is $(tput setaf 2)Allowed$(tput sgr0 0)\n" && false )) &&
((iptables -nL INPUT | grep tcp.*:$port > /dev/null && \
echo -e "\nPort $port is $(tput setaf 2)Allowed$(tput sgr0 0)\n") || \
echo -e "\nPort $port is $(tput setaf 1)Blocked$(tput sgr0 0)\n")

#end

for udp ports:

#Start

port=<PORT>; (iptables -nL INPUT | head -1 | grep "DROP" > /dev/null || \
( echo -e "\nPort $port is $(tput setaf 2)Allowed$(tput sgr0 0)\n" && false )) &&
((iptables -nL INPUT | grep udp.*:$port > /dev/null && \
echo -e "\nPort $port is $(tput setaf 2)Allowed$(tput sgr0 0)\n") || \
echo -e "\nPort $port is $(tput setaf 1)Blocked$(tput sgr0 0)\n")

#end

 

Following image shows examples of checking if HTTP ports 80(http) and 22(ssh) are enabled on the server or not.

NOTE : This command does not consider ports defined in ranges.