BookNest's API connects to PostgreSQL 1,289 on port 5432, and browsers connect to the API on port 3000. Each container has its own network namespace (Network and IPC Namespaces), so Docker 514 wires them together with network drivers: bridge (the default, a virtual switch on one host), host (no isolation), none (no network), overlay (spanning hosts) and the rarer macvlan and ipvlan, which put containers directly on a physical LAN. The listings run in one session from the directory that contains booknest, with the booknest.env file from Environment Variables.