TLSFailureException in UCMA 4.0 application after upgrading to Skype for Business 2015

Question

I have a UCMA 4.0 application written in c# that allows for custom management of user presence. Up until this weekend it had been communicating with our server running Lync 2013 and working fine. This weekend the server was upgraded to Skype for Business 2015 which shouldn't cause any problems for UCMA 4.0 applications according to Microsoft . Yesterday, Monday, my application was working fine with the new version but today I saw that they were down and I've been unable to get them to stay connected to the server. I've been getting the following error:

Exception Info: Microsoft.Rtc.Signaling.TlsFailureException Stack:
at Microsoft.Rtc.Signaling.QueueWorkItemState.ExecuteWrappedMethod(System.Threading.WaitCallback, System.Object) at System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object, Boolean) at System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object, Boolean) at System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem() at System.Threading.ThreadPoolWorkQueue.Dispatch()

I found an article about a similar problem saying that it is caused when the server hosting the UCMA application does not like the certificate coming from the Lync/Skype server . From there I checked the "System" Windows Log from the Event Viewer on my UCMA application server and found the following error from the "Schannel" source:

The certificate received from the remote server does not contain the expected name. It is therefore not possible to determine whether we are connecting to the correct server. The server name we were expecting is sip.domain.com. The SSL connection request has failed. The attached data contains the server certificate.

Does anyone have an idea what might have changed to cause this?

Answer 1

I solved the issue by renewing the certificate on my Lync/Skype server to include "sip.domain.com" as one of the "Subject Alternative Name" entries. This allowed my UCMA server to accept communications from the Lync/Skype server.

However, I still don't understand why this change was needed as everything was working fine under Lync 2013 and no changes were made to certificates during the Skype for Business 2015 upgrade.