cant connect

We are trying to use psql on RedHat 5.2 to access a database on another
Redhat 5.2 box runing Postgres (started as user postgres:     postmaster
-D /var/lib/pgsql -B 256 -i -d 3 &.)
The backend start okay and we can access the data on the local machine
runing psql but cannont on another machine on the same net.  We tried
adding PAM modules and adding the tcp port to the services files.  We
tried to log in as many different users but it just keeps telling us on
the remote and local machine that authenication has failed.  What could
we be doing wrong?  Any help would be greatly appreciated.

Joe