Configure PostgreSQL to work for only LOCALHOST or specified ip + port

The easiest way is to make PostgreSQL listen only on localhost for incoming connections. The relevant parameter is listen_addresses in postgresql.conf. The doc is here.

The following pg_hba.conf allows local and specified Ip have privilege login， but reject others。

# TYPE  DATABASE        USER            ADDRESS                 METHOD
local   all             all                                     trust
host    testdb          testuser      192.168.1.1/32             md5
host    all             all           0.0.0.0/0                 reject