Help me bring my Ubuntu Firewall back to normal

I messed up my Ubuntu server. Here were a few things I did: # iptables -L -t nat -v # iptables-save | iptables-restore # sudo iptables -P INPUT ACCEPT # sudo iptables -P OUTPUT ACCEPT # sudo iptables -P FORWARD ACCEPT # sudo iptables -F Here is what 'iptables-save' looks like: # Generated by iptables-save v1.6.0 on Fri Jul 6 04:38:15 2018 *filter :INPUT ACCEPT [324:22742] :FORWARD ACCEPT [0:0] :OUTPUT ACCEPT [283:49670] COMMIT # Completed on Fri Jul 6 04:38:15 2018 I was trying to block off a DOS attack. I needed to open only a few ports. I couldn't even start MongoDB now. Please help. We will communicate through TeamViewer.