Glossary: Rust in Practice

Host addresses (127.0.0.1, 0.0.0.0)

Also written: 127.0.0.1, localhost, loopback address, 0.0.0.0

127.0.0.1 (localhost) always means 'this same computer', so a service listening on it can only be reached from the machine it runs on, which suits local development. 0.0.0.0 means 'listen on every network interface', so other machines can reach the service too.