By default SQL Server listens on TCP port number 1433, but for named instances the TCP port is dynamically configured. There are several options available to get the listening port for a SQL Server named instance.
Here is one way to get this information.
SQL Server Configuration Manager
1. Go to Start > All Programs > Microsoft SQL Server 2008 > Configuration Tools > SQL Server Configuration Manager.
2. Go to SQL Server Configuration Manager > SQL Server Network Configuration > Protocols for <your Database>.
3. Right click on TCP/IP and select Properties.
4. In the TCP/IP Properties dialog box, select the IP Addresses tab and scroll down to the IPAll group.
If SQL Server is configured to run on a static port, the port number will be available in the TCP Port box. If it is configured on a dynamic port, the current port number will be available in the TCP Dynamic Ports box.
In the above example, the instance is listening on port number 49299.