PostgreSQL - Listen on All IPs

PostgreSQL version: 9.6
OS: Red Hat Enterprise Linux Server release 7.2 (Maipo)

By default, PostgreSQL is configured to listen to "localhost" on port 5432.

# netstat -atnp | grep 131069
tcp        0      0 127.0.0.1:5432            0.0.0.0:*               LISTEN      131069/postmaster

If you try to connect to the database from its public IP:

# psql -h 10.77.1.235 -U username

You will ge:

psql: could not connect to server: Connection refused
 Is the server running on host "10.77.1.235" and accepting
 TCP/IP connections on port 5432?

In order to open up the connection, you need to update "postgresql.conf" and "pg_hba.conf" files. In my case, I am running "postgresql-9.6", so two files are located at:

/var/lib/pgsql/9.6/data/postgresql.conf
    - To have postgresql listening on 0.0.0.0
/var/lib/pgsql/9.6/data/pg_hba.conf
    - To allow incoming connections

Configuring postgresql.conf
Open postgresql.conf file and update line

listen_addresses = 'localhost'                  # what IP address(es) to listen on
to
listen_addresses = '*'                  # what IP address(es) to listen on

Configuring pg_hba.conf
Open pg_hba.conf file and update line

host    all             all             127.0.0.1/32            ident
to
host    all             all             0.0.0.0/0               trust

Now restart the service:

#  systemctl restart postgresql-9.6.service

Try command "psql -h 10.77.1.235 -U username" again, you should be able to login.

# psql -h 10.77.1.235 -U username
psql (9.2.18, server 9.6.4)
WARNING: psql version 9.2, server version 9.6.
         Some psql features might not work.
Type "help" for help.

username=>