The default instance of SQL Server will listen on port 1433 (unless you’ve changed it to something else). However, by default, named instances will use a dynamic port, and SQL Server Browser will determine which port has been allocated and direct traffic accordingly. This works well if you’re running multiple instances on your local machine, but is not so good in corporate and other environments where you need a fixed port number so you can open specific firewall ports. Fortunately it’s fairly easy to change to a fixed port (or to change the port number) once the instance has been installed.