WSUS Version 6
Just spent ages trying to figure out why my nice shiney new WSUS service running on Server 2012 could not connect to clients and vice versa. Turns out it installs to port 8530 in IIS, instead of 80 as in previous versions.
You have to specify the port as well now in group policy so instead of http://servername is http://servername:8530
Even when I'd found the solution through trial and error it's damn difficult to find any references to this online!
Thought this might help someone!
It's always picked that port if something else is running on port 80 on the older version.
I just changed my instance in IIS to run on port 80 and that did the trick.