You configure a new SQL Server 2005 computer to use TCP/IP with all default settings. Your corporate policy requires that each server use a firewall. You find that you can connect to the SQL Server instance from the local computer. However, client computers cannot connect to the SQL Server instance.
You need to identify the most likely cause of the connection issues. What should you do first?

A.
Ensure that port 1433 is open in your firewall.

B.
Ensure that port 443 is open in your firewall.

C.
Ensure that client computers connect by using Shared Memory protocol.

D.
Ensure that the server is not paused.

Explanation:
The default instance of the Database Engine uses port 1433, but that can be changed. Instances of SQL Server 2005 Express Edition, SQL Server Mobile, and named instances of the Database Engine use dynamic ports. The SQL Server Browser service lets users connect to instances of the Database Engine that are not listening on port 1433, without knowing the port number. To use SQL Server Browser, you must open UDP port 1434.