postgresql port (5432) is closed

hi all

how can i open postgresql port (5432), in order i execute 'nmap localhost'
and i see port scanned on display,because my port not list

Port        State       Service
5432/tcp  open     postgresql

in the last that port is opened, but now is closed(port has't scann),so what
can i do?


Best Regards,

-devi munandar