SQL Server Access from remote client machines: If you have a named instance of SQL Server, then there are specific things you need to do to allow clients to access the SQL database remotely. The default instance of SQL Server uses port 1433. Even for the default instance you will probably want to open an Inbound Rule on the SQL host that allows any inbound communication on port 1433 or allows the sqlsvr.exe access via this port. For named instances, the ports that are used to talk to the SQL box are by default dynamic. The SQL browser can advertise the exact ports used by the named instances if UDP is allowed through the firewall on port 1434. A complete explanation of these issues can be found in this document: [more] http://blogs.technet.com/b/nexthop/archive/2011/04/12/using-lync-server-2010-with-a-custom-sql-server-network-configuration.aspx . This document specifically addresses the LYNC client connection, but the principals are the same regardless of the application.