Port in use, but no process in sight

A service fails with Address already in use, but ss -lntp | grep 8080 is empty.

Possibilities. The process lives in another network namespace — invisible to host ss but really holding the port; use nsenter -t <pid> -n ss -lntp. Or 8080 has many TIME_WAIT sockets and SO_REUSEADDR is not set: ss -tan shows them, -l does not. Or the port falls inside net.ipv4.ip_local_port_range and the kernel is using it as an ephemeral port. Or ss -p simply lacked root and showed no process column.