Host addresses (127.0.0.1, 0.0.0.0)

Also written: 127.0.0.1, 0.0.0.0, loopback address, loopback, every address

127.0.0.1 is the loopback address, which a host uses to talk to itself: a service listening only there works on the server but can't be reached from Priya's laptop. As a listening address, 0.0.0.0 means "every address this host has"; it is also the source address of a DHCP Discover from a laptop that has no address yet.