TCP 6379 is the default network port used by Redis for client connections. In practice, it is the door through which applications send commands to a Redis server, such as reading and writing cached data, queues, and session state.
In cyber security, this port matters because services listening on 6379 are often easy for internet scanners to find. If Redis is exposed without authentication or network restrictions, attackers can connect directly and abuse the service to run commands, plant files, or support malware deployment. That can turn an ordinary cache into a compute resource for cryptomining or a foothold for further abuse. Defenders should keep Redis bound to trusted interfaces, block public access with firewalls, enable authentication and protected mode, and monitor for unexpected connections to port 6379.