Jeff, Andrew, Andreas: Thank you for your replies.
Environment is Mageia 6 x86_64. I think the packagers must have set up
the 5433 port (although I notice the documentation for pg_ctl contains
several examples using 5433).
Anyway, I am relieved that 5432 is still regarded as the main port, and
have changed all port references to that.
Regards
Graeme