Finding the Port Number for a particular SQL Server Instance

DECLARE @tcp_port NVARCHAR(5)

EXEC xp_regread @rootkey = ‘HKEY_LOCAL_MACHINE’
 ,@key = ‘SOFTWARE\MICROSOFT\MSSQLSERVER\MSSQLSERVER\SUPERSOCKETNETLIB\TCP’
 ,@value_name = ‘TcpPort’
 ,@value = @tcp_port OUTPUT

SELECT @tcp_port