{
  "port": 4000,
  "protocol": "tcp",
  "service": "Phoenix / Jekyll dev servers (IANA: Terabase)",
  "oneLiner": "A very common local development-server port — Phoenix and Jekyll both default to it — with a long tail of legacy and game traffic behind it.",
  "whatItIs": "IANA registers 4000 as terabase, which you will never meet. What actually binds 4000 today is development tooling: Elixir's Phoenix framework accepts requests on 4000 by default, and `jekyll serve` defaults to 4000 too. Historically the port carried the legacy Mirabilis ICQ client, Diablo II multiplayer, and the RemoteAnything remote-control product, which is why old scanner databases and firewall rulesets attach suspicious labels to it. On a modern host, 4000 is a developer's machine or a container running a dev build far more often than anything else.",
  "exposure": {
    "verdict": "careful",
    "note": "A framework dev server here has debug pages, stack traces and live reload and must not face the internet; a real application behind a reverse proxy on 4000 is fine."
  },
  "checkCommand": "curl -sI http://localhost:4000/",
  "links": [
    {
      "title": "Phoenix — Up and Running (\"By default, Phoenix accepts requests on port 4000\")",
      "url": "https://phoenix.hexdocs.pm/up_and_running.html",
      "kind": "official-docs"
    },
    {
      "title": "Jekyll — Configuration options (serve port defaults to 4000)",
      "url": "https://jekyllrb.com/docs/configuration/options/",
      "kind": "official-docs"
    },
    {
      "title": "phoenixframework/phoenix on GitHub",
      "url": "https://github.com/phoenixframework/phoenix",
      "kind": "github"
    },
    {
      "title": "IANA port registry — 4000 (terabase)",
      "url": "https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml?search=4000",
      "kind": "iana"
    }
  ],
  "ianaName": "terabase"
}