## find ports listening
netstat -an | grep 8000
netstat -an | grep LISTEN
## test connection
telnet 10.0.3.30 8000
## find ports listening
sudo ss -tulpn | grep 8000
tcp LISTEN 0 10 0.0.0.0:8000 0.0.0.0:* users:(("python3",pid=273874,fd=4))
## firewall rules
sudo iptables -L INPUT -n -v
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
6207K 25G ACCEPT 0 -- * * 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED
4 336 ACCEPT 1 -- * * 0.0.0.0/0 0.0.0.0/0
260K 27M ACCEPT 0 -- lo * 0.0.0.0/0 0.0.0.0/0
13 780 ACCEPT 6 -- * * 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:22
247 10680 REJECT 0 -- * * 0.0.0.0/0 0.0.0.0/0 reject-with icmp-host-prohibited
0 0 ACCEPT 6 -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:8000
0 0 ACCEPT 6 -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:8000
0 0 ACCEPT 6 -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:8000
## list firewll rules
sudo iptables -L INPUT --line-numbers -n
Chain INPUT (policy ACCEPT)
num target prot opt source destination
1 ACCEPT 6 -- 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:3000
2 ACCEPT 0 -- 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED
3 ACCEPT 1 -- 0.0.0.0/0 0.0.0.0/0
4 ACCEPT 0 -- 0.0.0.0/0 0.0.0.0/0
5 ACCEPT 6 -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:8000
6 ACCEPT 6 -- 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:22
7 REJECT 0 -- 0.0.0.0/0 0.0.0.0/0 reject-with icmp-host-prohibited
8 ACCEPT 6 -- 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:3000
## delete line 5
sudo iptables -D INPUT 6
## add new rule above REJECT
sudo iptables -I INPUT 5 -p tcp --dport 8000 -j ACCEPT
sudo netfilter-persistent save
## create server process to listen port 5432
nc -l -p 5432
