This module allows one to list and optionally filter remote addresses of an incoming request, as populated by the HTTP X-Forwarded-For header.

It works with both IPv4 and IPv6 and can filter addresses using pre-defined names like "loopback", "linklocal" or "uniquelocal" (which are expanded internally into IP addresses or ranges), or using a custom function.

Node.js is an event-based server-side JavaScript engine.