net.port

export type Protocol = "tcp" | "udp";

export type PortRange = "system" | "user" | "dynamic";

/** A port, the range RFC 6335 puts it in, and the service registered on it. */
export interface PortService {
  readonly port: number;
  readonly protocol: Protocol;
  readonly range: PortRange;
  /** IANA service name, null when this registry has none for it */
  readonly service: string | null;
  readonly description: string | null;
}

export function isPort(value: number): boolean

import { isPort } from "#fune/net.port@^1";

/**
 * Whether a number is a usable TCP or UDP port: a whole number from 1 to
 * 65535. Port 0 is reserved (RFC 6335) and asks the operating system to pick
 * one, so it is never a port to connect to.
 */
export function isPort(value: number): boolean {
  return typeof value === "number" && Number.isInteger(value) && value >= 1 && value <= 65535;
}

export function portService(port: number, protocol: Protocol): PortService

import { portService } from "#fune/net.port@^1";

import { isPort } from "./net_port_is_port.ts";  ← isPort, another function of this group · built into the same file, even by a slim install
import { SERVICES } from "./net_port_data.ts";  ← this capability’s own data, compiled from data/services.json into the same file by fune build
import { type PortRange, type PortService, type Protocol } from "./net_port_types.ts";

/**
 * The RFC 6335 range a port is in, and the IANA service registered on it for
 * a protocol. A port with nothing in this registry's table has a null service:
 * unassigned, or assigned but not common enough to ship here.
 */
export function portService(port: number, protocol: Protocol): PortService {
  if (typeof port !== "number" || !Number.isInteger(port)) throw new TypeError(`port must be an integer, received ${port}`);
  if (!isPort(port)) throw new RangeError(`port must be 1 to 65535, received ${port}`);
  if (protocol !== "tcp" && protocol !== "udp") throw new RangeError(`protocol must be tcp or udp, received "${protocol}"`);
  // RFC 6335 section 6: system 0-1023, user 1024-49151, dynamic 49152-65535.
  const range: PortRange = port <= 1023 ? "system" : port <= 49151 ? "user" : "dynamic";
  const row = SERVICES.find((s) => s.port === port && s.protocol === protocol);
  return { port, protocol, range, service: row ? row.service : null, description: row ? row.description : null };
}

Install

fune build

With that line in your source, in a TypeScript project (language typescript in fune.project), fune build resolves it and nothing else, pins them in fune.lock, downloads only the TypeScript package of each, and builds the code above into your project’s .fune/build, one readable file per capability with a header linking back here. Or pin a range in fune.project and build in one step:

fune add net.port

That builds the whole group. To build only what you call, and whatever it uses inside the group:

fune add net.port --only isPort

The manifest, vectors and README with only the TypeScript implementation. Install it without the registry with fune add ./net.port-1.0.0-typescript.fune, or fetch it from a terminal with fune pull net.port@1.0.0:typescript.

The whole function, every language, is one file too: net.port-1.0.0.fune, 33,904 bytes, sha256 b4abf0a4585a74e0ed2cb54fce546dc137d24a263d490d0705b908921f46fd33. It installs into a project of any language.

// fune: before net.port.isPort
// fune: before net.port.portService

// fune: after net.port.isPort
// fune: after net.port.portService

// fune: step net.port.<fn> after <n|label>

More from the author

They are a group because `portService` is only defined on what `isPort` accepts; a caller validating an inventory wants the first, one labelling a report wants the second.

## Ranges (RFC 6335 section 6)

| range | ports | | |-------|-------|--| | `system` | 0-1023 | assigned by IETF review; binding needs privilege on Unix | | `user` | 1024-49151 | assigned by IANA on request | | `dynamic` | 49152-65535 | never assigned; ephemeral client ports |

Port 0 is reserved and means "let the OS pick", so `isPort(0)` is false.

## The service table

`data/services.json` holds 144 rows (76 ports, tcp and udp) copied verbatim from the IANA Service Name and Transport Protocol Port Number Registry: the service name and description exactly as IANA writes them, including its capitalisation. It is a subset: the ports an operations team meets (ssh, dns, http/https, mail, directory, databases, message brokers, remote access, VPN). A port not in the table has `service: null`, which means "not in this table", not necessarily "unassigned".

Choices where IANA lists more than one name on a port/protocol:

- 80: `http` (IANA also lists `www` and `www-http` as aliases). - 465/tcp: `submissions` (RFC 8314), not the historical `urd`. - 2049: `nfs`, not `shilp`. - Everywhere else, the first name IANA lists. Rows IANA marks `Reserved` (e.g. 6379/udp, 993/udp) are left out, so they have no service.

Notable answers: 5433 is registered to `pyrrho` (Pyrrho DBMS), not to a second PostgreSQL, however often Postgres is run there; 4874 is unassigned (IANA lists 4872-4875 as Unassigned).

Source: IANA, "Service Name and Transport Protocol Port Number Registry", https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.csv, fetched 2026-09-26. RFC 6335 (Procedures for the Management of the Service Name and Transport Protocol Port Number Registry), section 6, for the ranges.

Files