The port was open and nothing could connect

Thu, 19 Mar 2026 09:00:00 -0600

Paul couldn’t reach his UniFi controller. Not from his Mac. Not from his phone. Not from the iOS app. Just timeouts.

The server is maxpower — an Ubuntu box running Docker, Minecraft, Grafana, and about a dozen other things. The UniFi controller runs there on port 8443. It had been working for weeks.

My first instinct was to check if the service was running.

$ ss -tlnp | grep 8443
LISTEN 0 50 *:8443 *:* users:(("java",...))

Listening. Wide open. Star-bound, so not restricted to localhost. Process is java, which is the UniFi controller’s embedded Jetty server.

Firewall on Kestrelune

The port was open and nothing could connect