{
  "port": 20221,
  "protocol": "both",
  "service": "Unassigned",
  "oneLiner": "The last number in an unassigned IANA block, sitting directly below the registered 20222.",
  "whatItIs": "IANA's unassigned range 20203-20221 ends here, and the very next port, 20222, is registered as iPulse-ICS — so 20221 is often scanned as the low half of a presumed pair even though nothing is assigned to it. Nmap carries it as 'unknown' on both TCP and UDP with a small open-frequency, which is enough to put it in the default top-1000 scan. There is no documented protocol for this number.",
  "exposure": {
    "verdict": "careful",
    "note": "Nothing standard listens here, so an open port is an unknown application. Fingerprint it and judge that, not the number."
  },
  "checkCommand": "nmap -Pn -sV -p 20221 --reason TARGET",
  "links": [
    {
      "title": "IANA Service Name and Transport Protocol Port Number Registry",
      "url": "https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml",
      "kind": "iana"
    },
    {
      "title": "Nmap nmap-services frequency table",
      "url": "https://github.com/nmap/nmap/blob/master/nmap-services",
      "kind": "github"
    }
  ]
}