Hi there :)
To cut a looong story short, because i have spent all day + evening in the same boat as you
here is what i found.
1. Turn ON your windows firewall
2. Turn OFF BD 2015 firewall
3. goto : allow a program or feature through Windows firewall,
and make sure your DCS .exe`s are allowed in there.
4. Now fire up DCS World and connect.
5. Turn ON your precious BD 2015 firewall again, and make sure to go and turn OFF
windows firewall.
All i can say is : that`s what i did and im now a happy online flying Viking again :)
Hope it can help you and other`s too.