I would like to help me check the active rules in the iptables firewall. My S.O is Ubuntu Server 14.04.3 LTS Trusty.
You can list the rules with the following two commands:
sudo iptables -v -x -n -L sudo iptables -t nat -v -x -n -L
Those are the ones I prefer, because it can be informative to observe the packet counters, particularly when trying to debug. Also, not doing name resolution can save a lot of time.
However, there is another command, which pretty much provides the same information:
sudo iptables-save -c