any tips to have restricted inbound and getting connected with postgresql dB

[Y_Bharani_mbsv]

  TeamI have the need to have postgresql db running in multiuser mode and do my 
needed tasks for few mins.
How to restrict all the application layer , not to get connected with the 
postgres db ,during my specific time window I am aware of their application 
layer - username
Changing password is the last option
Any tips