You can use the os Module:
var os = require("os"); os.hostname();
if you can work with the IP address -- Machines may have several Network Cards and unless you specify it node will listen on all of them, so you don't know on which NIC the request came in, before it comes in.
Hostname is a DNS matter -- Don't forget that several DNS aliases can point to the same machine.
~ Answered on 2012-02-22 17:20:07