Opening a port in a router or firewall residing in a private network in order to let a party from the outside world contact a user inside. For example, opening ports for VoIP and videoconferencing traffic makes two-way communications easier no matter which side initiates the call. Also called "port mapping," port forwarding can be done by manual configuration or by software such as UPnP, Zeroconf and Jini. See UPnP, Zeroconf, Jini and TCP/IP port.