When I run on my instance (dynamic port) this gives null . Not much use

Following gives the port

declare @tcpport varchar(1000),@value varchar(250);set @tcpport = 'SOFTWARE\Microsoft\Microsoft SQL Server\' + @@servicename + '\MSSQLServer\SuperSocketNetLib\Tcp';EXEC master..xp_regread @rootkey = 'HKEY_LOCAL_MACHINE', @key = @tcpport, @value_name = 'tcpPort', @value = @value OUTPUT;select @value