Check who's pinging my server and accessing other ports

sudo tcpdump -nnvXSs 0 -c2 icmp -- ping check
sudo tcpdump port 8080

Redirect ports in Ubuntu using iptables command

 Following code redirect all incoming traffic to port 7001 to 80

 sudo iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 7001 -j REDIRECT --to-port 80

Following code redirect all incoming traffic to port 7001 to 8080

 sudo iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 7002 -j REDIRECT --to-port 8080