postgres connection issues

I searched the web and all what I tried did not work. So please bear with me:

I trying to access a database on a linux machine from a windows computer using SQuirrel:

postgres version 9.4.5

Squirrell version 3.7

However, I am getting the error message on SQuirrel:

Connection to host:5432 refused. Check that the hostname and port are correct and that the postmaster is accepting TCP/IP connections

This is what I have done:

a) Changed postgresql.conf: listen_addresses = '*'

b) edited pg_hba.conf: host all all 127.0.0.1/32 trust

    host all all 0.0.0.0/0 trust

c) The server is running and listening at the correct port on the linux site:

   ps -efl | grep postgres

    netstat -nlp | grep postgres

What else could I try to enable a communication?

Any suggestion is highly appreciated.

Best,

Markus