Check port status
# `(echo >/dev/tcp/${host}/${port})`
(echo >/dev/tcp/192.168.57.24/80) &>/dev/null && echo "open" || echo "closed"
timeout 1 bash -c '>/dev/tcp/192.168.57.24/80 &>/dev/null' && echo "open" || echo "closed"
timeout 1 bash -c '>/dev/tcp/192.168.57.24/80' && echo "open" || echo "closed"
Block subnets
ip route add blackhole 192.168.0.0/24
Kill sessions
# ss
sudo ss -K state TIME-WAIT
# or conntrack
sudo conntrack -D -p tcp --state TIME_WAIT