Asking for advice - Ubuntu local Firewall to log processes network activity

[Wolfgangthegreat]

Hello,

I am looking for an advice:
To complement PFS, I wish to install on my backend server, Ubuntu, a local Firewall (or similar idea) to log processes network activity, so I know which process tried to access what or received a connection.

I need it to run constantly, not a one time thing like tcpdump, something more neat, possibly even commercial.

Do you have an idea?