2 entries are registered on port 20000. It is a registered port (1024–49151) — IANA records an assignee, but nothing stops other software from listening here, which is why the number carries more than one entry.
01DNP3no transport recorded · iana-registered · risk 4/10
DNP3 (Distributed Network Protocol) is a robust communication protocol widely used in SCADA (Supervisory Control and Data Acquisition) systems to enable reliable data exchange between control equipment such as Remote Terminal Units (RTUs) and Intelligent Electronic Devices (IEDs). Designed for electrical and utility automation sectors, DNP3 ensures efficient and dependable device interoperability across complex supervisory networks.
Usermin is a web-based interface that allows users to manage various aspects of their UNIX/Linux accounts. It provides functionalities like changing passwords, managing email filters, viewing emails, and editing files through an easy-to-use GUI accessible via web browsers.
The registry says what 20000 is registered to. What is listening on it right now is decided by the host, and only the host can be asked. Each of these prints the process behind the socket.
linux
ss -ltnp | grep ':20000\b'
macos
lsof -nP -iTCP:20000 -sTCP:LISTEN
windows
netstat -ano | findstr :20000
On Linux and Windows the process name comes back with the socket; on macOS lsof needs sudo to name a process that isn't yours. Match what it prints against the 2 entries above.
A port number is not a service. Anything may listen on 20000 — what you actually met is decided by the host, not the registry. If a service is missing here, it belongs in the registry.