Sunday, October 13, 2013

SQL 2012 Not Listening on TCP1433

Previous releases of Microsoft SQL such as 2008 R2 use to listen on TCP1433 for incoming SQL traffic.  Now in SQL Server 2012, TCP1433 is no longer utilised.  This can be shown using the netstat command as shown in the screenshot below.

SQL Server 2012 now uses dynamic ports for each SQL instance which is subject to change.  SQL client applications discover the which port the instance is now running on by querying UDP 1434, the SQL Browser Service which returns the correct port.  My SQL Server instance is currently running on TCP25463 and the Browser Service tells the client to connect to this port.

This is similar to the way the RPC Endpoint Mapper works for RPC based Microsoft applications.  In terms of network lockdown and ACL rules, the network engineers are usually unhappy about this approach as it means they need to keep the entire port range open.


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