one of our EC2 instances got broken all of a sudden and we couldn't reach it. It's running a Spotfire Server (i.e. Tomcat web app). I ran nmap -Rn- <IP-address> I found out that the only open port is 22. Port 80 is closed and I don't know why it got closed all of a sudden.
What would be the best way to get that port opened? I searched online and people seem to suggest installing firewall-cmd (it's not installed at the moment) but I am wondering if that is a good idea as, after all, we have "Security Groups" on AWS which serves as a firewall.
What would be the best way to re-open port 80?
Note: I checked the security groups for the EC2 instance and according to it the port should be open:
