declare @PortNumber as varchar(8) 
exec xp_regread 
	@rootkey = 'HKEY_LOCAL_MACHINE', 
	@key = 'SOFTWARE\MICROSOFT\MSSQLSERVER\MSSQLSERVER\SUPERSOCKETNETLIB\TCP', 
	@value_name = 'TcpPort', 
	@value = @PortNumber output 
select @PortNumber [TCP Port]