Remote Access to pgsql DB ???

Hi,

I have a question about remote access to Pgsql DB. I acctually want to
access mydb which located on a Unix server called ORION from another
Unix server called OMEGA.

According to documentation I have to run postmaster on ORION with -i
option like:

/usr/local/pgsql/bin/postmaster -i -D /usr/local/pgsql/data &

 so I have done that, I also changed pg_hba.conf  on ORION  for  OMEGA
IP address like:

host         all         172.21.2.41    255.255.255.255     trust

But still I can not run psql mydb from Omega:

psql: connectDBStart() -- connect() failed: Connection refused
        Is the postmaster running locally
        and accepting connections on Unix socket '/tmp/.s.PGSQL.5432'?

Why should I get this error when I have run postmaster with -i on ORION?

Shall I run that on OMEGA as well, then it's not a remote access?!!!

I appreciate your help!

Thanks in advance,
Fariba