Hello (again),
i'm searching for an Firewall on application level. I only want to open/block ports for some application, not for all applications. More specific: i want to create rules specific for applications.
I found Douane, but it seems its abandoned (last update on the gitlab page was 4 years ago).
On Windows i use Binisofts "Windows Firewall Control", which exactly does what i want.
Can someone recommend me such an firewall for Zorin/Ubuntu?
Thanks in advance!
I believe that you're looking for something like Firejail:
I don't use it myself, but I know a few people that do. It sounds like it's the thing that you'd be looking for.
GUFW (Gnome Uncomplicated Fire Wall) already has this functionality. It has a raft of application rules that can be added or you can add your own.
If you already know which ports the application uses, you can just create rules on the default firewall — you will find that under applications menu as "Firewall Configuration".
For something more specific, the only options that I know are OpenSnitch and Portmaster. Keeping in mind that this last option is a more generalized solution that does can do a lot more, and is therefore more complicated to use. I've used it briefly but didn't have a good experience with it. It's probably evolved since then, so I'd encourage you to try it anyway to see how you like it.
Thanks everyone for answering.
@swarfendor437 I'm too stupid to figure out, how i can add specific WINE/Proton applications in GUFW. I was able to add WINE and WINESERVER, but then all applications using WINE would have access to the internet.
@applecheeks37 From reading the description and looking at some explanation on this tool, it sounds very powerful and a bit too powerful for my cases 
@zenzen I looked at both tools and i think OpenSnitch or Portmaster will fit. I currently try Portmaster and will let you know the results, when i have some.
Thanks again everyone!
I've read a while ago about Nethsecurity but I don't know if this is maybe too big for Your Needs. But if You want to take a Look at it ...
Does the posted solution with 40 votes on this askubuntu thread help?: