We got a report about this from another user with the 3.0.6 version.
We have not yet verified if this is an issue on our commercial clients as well, but if it is we will patch asap and publish the client on github so that the users of 3.0.6 can implement a solution based on our official client if they want to.
For more info about the KB breaking TLS/SSL see https://connect.microsoft.com/VisualStudio/Feedback/Details/2590316
So it seems to be a general issue
Regards, Uffe
Team XSockets.NET