Postgres does not accept socket connections

Hi All,

I have the following problem.

I am able to access a PostgreSQL database only as "localhost". If I try
to open psql from a different machine with -h option, then I get the
following error message.

The database resides on a server running Fedora Core 4 and PostgreSQL
8.1.1 server.
I am trying to access the database from another server running RedHat 9
and PostgreSQL 7.3.2.

Command
psql -U postgres -h server-name database-name

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

Similarly, I am unable to access the database using  PHP's postgres
API, with the host set as "server-name". However, I am able to locally
access if I specify host as "localhost".

I need the PostgreSQL server on the machine which contains the database
to accept socket connections.
Any help in this regard will be appreciated.

Thanks in advance
- Kishore