[Warning] Could not confirm port 10999 is open in the firewall

Hi! 

Here's what happens: I start a new server since the update, with mods (refreshed, updated. I've even cleaned them all out - unsubscribed and subscribed to only updated ones). The game runs fine for a while and after 5 minutes or so the disconnected icon pops up in the top left. I think my firewall is blocking it somehow. I'm using McAfee (paid version)

What I've tried:

• turning off firewall
• turning off real time scanning
• editing the rights of dst client, steam exe, and all associated programs through (bypassing NetGuard)
• Changing the port in the server.ini and client.ini file as well as Caves

I hope someone can help me. It only began after the recent update (Waterlogged, I believe).