No, it isn't. Verify with
ping localhost
which will show you the IP address that localhost resolves to.
The “loopback interface” is a special network interface that only contains your computer.
The cause of the problem is probably that the PostgreSQL parameter listen_addresses, which specifies the network interfaces on which PostgreSQL is listening, is set to the default value localhost.
Change the value to * and restart PostgreSQL, and it should work.
A second possibility is that you have restrictive firewall settings on your machine. Actually, reading your question again, that is probably your problem, since you are receiving no response rather that an error saying that nothing is listening on that port.