{
  "port": 51103,
  "protocol": "tcp",
  "service": "Unassigned (dynamic range)",
  "oneLiner": "No IANA assignment and no documented service, though it is seen slightly more often than its neighbours.",
  "whatItIs": "51103 lies in the Dynamic/Private range that RFC 6335 closes to registration. Nmap's service database has no name for it but records a measurably higher open-port frequency than most of the 51000s, which is consistent with a peer-to-peer or client application that reuses a fixed high port rather than with any registered service. Without a name in the primary references, the only honest description is an unassigned port with an application squatting on it.",
  "exposure": {
    "verdict": "careful",
    "note": "Ports that recur across unrelated hosts usually belong to consumer software opening its own listener; identify the application before allowing it inbound."
  },
  "checkCommand": "nmap -Pn -sV -p 51103 TARGET",
  "links": [
    {
      "title": "Nmap source repository (nmap-services port frequency database)",
      "url": "https://github.com/nmap/nmap",
      "kind": "github"
    },
    {
      "title": "RFC 6335 — IANA Procedures for Service Name and Transport Protocol Port Number Registry",
      "url": "https://www.rfc-editor.org/rfc/rfc6335.html",
      "kind": "spec"
    }
  ]
}