netcat, netstat, iptables reject

netcat-iptables.txt

https://unix.stackexchange.com/questions/457670/netcat-how-to-listen-on-a-tcp-port-using-ipv6-address
https://github.com/craSH/socat/blob/master/EXAMPLES
https://serverfault.com/questions/353985/socat-show-incoming-connections
socat -d -d -6 tcp6-listen:5555 stdio
socat -d -d -6 tcp-connect:[ipv6]:88 stdio

https://stackoverflow.com/questions/5106674/error-address-already-in-use-while-binding-socket-with-address-but-the-port-num
http://www.softlab.ntua.gr/facilities/documentation/unix/unix-socket-faq/unix-socket-faq-2.html#time_wait
netstat -Waptun |grep 5555
ss -aptun | grep 5555

https://unix.stackexchange.com/questions/124624/what-a-input-j-reject-reject-with-icmp-host-prohibited-iptables-line-does-ex
https://github.com/MaxKellermann/ferm/issues/10
https://linux.die.net/man/8/iptables
iptables -j REJECT -h | grep "Valid reject types" -A 17
 icmp-net-unreachable        ICMP network unreachable
 net-unreach                 alias
 icmp-host-unreachable       ICMP host unreachable
 host-unreach                alias
 icmp-proto-unreachable      ICMP protocol unreachable
 proto-unreach               alias
 icmp-port-unreachable       ICMP port unreachable (default)
 port-unreach                alias
 icmp-net-prohibited         ICMP network prohibited
 net-prohib                  alias
 icmp-host-prohibited        ICMP host prohibited
 host-prohib                 alias
 tcp-reset                   TCP RST packet
 tcp-rst                     alias
 icmp-admin-prohibited       ICMP administratively prohibited (*)
 admin-prohib                alias
iptables -I 
https://linux.die.net/man/8/ip6tables
ip6tables -j REJECT -h | grep "Valid reject types" -A 11
 icmp6-no-route              ICMPv6 no route				=> Network is unreachable
 no-route                    alias
 icmp6-adm-prohibited        ICMPv6 administratively prohibited		=> Permission denied
 adm-prohibited              alias
 icmp6-addr-unreachable      ICMPv6 address unreachable			=> No route to host
 addr-unreach                alias
 icmp6-port-unreachable      ICMPv6 port unreachable			=> Connection refused
 port-unreach                alias
 tcp-reset                   TCP RST packet				=> Connection refused

iptables -I INPUT 1 -p tcp --dport 70 -j REJECT --reject-with icmp-net-unreachable	=> Network is unreachable
iptables -I INPUT 1 -p tcp --dport 71 -j REJECT --reject-with icmp-host-unreachable	=> No route to host
iptables -I INPUT 1 -p tcp --dport 72 -j REJECT --reject-with icmp-proto-unreachable	=> Protocol not available
iptables -I INPUT 1 -p tcp --dport 73 -j REJECT --reject-with icmp-port-unreachable	=> Connection refused
iptables -I INPUT 1 -p tcp --dport 74 -j REJECT --reject-with icmp-net-prohibited	=> Network is unreachable
iptables -I INPUT 1 -p tcp --dport 75 -j REJECT --reject-with icmp-host-prohibited	=> No route to host
iptables -I INPUT 1 -p tcp --dport 76 -j REJECT --reject-with icmp-admin-prohibited	=> No route to host
iptables -I INPUT 1 -p tcp --dport 77 -j REJECT --reject-with tcp-reset			=> Connection refused

ip6tables -I INPUT 1 -p tcp --dport 70 -j REJECT --reject-with icmp6-no-route		=> Network is unreachable
ip6tables -I INPUT 1 -p tcp --dport 71 -j REJECT --reject-with icmp6-adm-prohibited	=> Permission denied
ip6tables -I INPUT 1 -p tcp --dport 72 -j REJECT --reject-with icmp6-addr-unreachable	=> No route to host
ip6tables -I INPUT 1 -p tcp --dport 73 -j REJECT --reject-with icmp6-port-unreachable	=> Connection refused
ip6tables -I INPUT 1 -p tcp --dport 74 -j REJECT --reject-with tcp-reset		=> Connection refused

for i in $(seq 70 77); do telnet ipv4 $i | grep telnet; done
for i in $(seq 70 74); do telnet ipv6 $i | grep telnet; done