What is the most efficient way to connect my application on one VM to my Postgres DB on another VM?

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http://serverfault.com – I have 1 physical machine with 2 VMs (VMWare esxi) - one for database (PostgreSQL 9.2.1), and one for application. I'd like my application to connect to my database in an efficient way, and I've heard that using a file system socket is more efficient than a network socket (TCP overhead, IIRC). Is there a way to use a file system socket with the aforementioned setup? Or... Is there another, efficient connection method you'd recommend? (HowTos)