Self Hosted WCF communication fails to DB

I have an application using WCF self-hosted services (connecting to an MSMQ). Using Entity Framework, I am trying to read some data from a database on another server, and get the following error. I'm not sure what the issue is here... though there is a firewall between the app and DB servers. We did open up SQL ports communication.

System.Data.Entity.Core.EntityException: The underlying provider failed on Open. ---> System.Transactions.TransactionManagerCommunicationException: Communication with the underlying transaction manager has failed. ---> System.Runtime.InteropServices.COMException: The MSDTC transaction manager was unable to push the transaction to the destination transaction manager due to communication problems. Possible causes are: a firewall is present and it doesn't have an exception for the MSDTC process, the two machines cannot find each other by their NetBIOS names, or the support for network transactions is not enabled for one of the two transaction managers. (Exception from HRESULT: 0x8004D02A)

What causes this error and how can I resolve it?