We can take a look at three different ways you can identify the port used by an instance of SQL Server.
Using Windows Application Event Viewer
USE master
GO
xp_readerrorlog 0, 1, N'Server is listening on', 'any', NULL, NULL, N'asc'
GO
Identify Port used by SQL Server Database Engine Using SQL Server Configuration Manager
Click Start -> Programs -> Microsoft SQL Server 2008 -> Configuration Tools -> SQL Server Configuration Manager
In SQL Server Configuration Manager, expand SQL Server Network Configuration and then select Protocols for on the left panel. To identify the TCP/IP Port used by the SQL Server Instance, right click onTCP/IP and select Properties from the drop down as shown below.
For More Help
http://sqlnetcode.blogspot.com/2011/11/sql-server-identify-tcp-ip-port-being.html