Install conntrackd by entering the following commands in the terminal:
sudo apt update sudo apt install conntrackd
Description:
Connection tracking daemon
Conntrackd can replicate the status of the connections that are currently being processed by your stateful firewall based on Linux. Conntrackd can also run as statistics daemon.
Homepage: http://conntrack-tools.netfilter.org/
Version: 1:1.4.4+snapshot20161117-6ubuntu2
Section: universe/net