Port 6379: Redis
Port 6379 is the default port for Redis, an in-memory database and cache.
What runs on port 6379
Redis listens on TCP 6379 and is used as a cache, message queue and session store behind many web apps. For years it shipped with no password by default and trusted anyone who could connect; since version 3.2 its protected mode refuses outside connections when no password is set.
On a home network
Home servers and Docker hosts running self-hosted apps (for example Nextcloud or Immich) often include Redis. It is not something consumer devices run.
If port 6379 is reachable from the internet
An exposed Redis without a password is one of the most exploited services on the internet. Attackers have used it to write their own SSH keys onto servers, drop cron jobs and install cryptominers, and several botnets scan specifically for 6379. Keep it bound to localhost or a private network.
How to check whether it is open on your network
Check your Redis bind and requirepass settings and whether a Docker container publishes 6379. RECON's Port Scan will show which LAN host runs it.
To find out whether port 6379 is open on something in your home, and whether the internet can reach it, the app scans your Wi-Fi from your phone and checks your public address from the outside. It says what it checked and what it could not. Get RECON for iPhone — one-time purchase, no account, nothing leaves the device.