Check all interfaces

Inspired by the implementation in
https://github.com/sindresorhus/get-port/blob/0760c987c17581395d4e30432881dcb0ca6ca94a/index.js, make sure the port
is available on all interfaces.

Author: novemberborn

source/index.ts

@@ -1,9 +1,16 @@
 import crypto from 'node:crypto';
 import net from 'node:net';
+import os from 'node:os';
 import {SharedContext} from '@ava/cooperate';
 
 const context = new SharedContext(import.meta.url);
 
+const localHosts = new Set([
+	undefined, // Default interfaces,
+	'0.0.0.0', // Ensure we check IPv4,
+	...Object.values(os.networkInterfaces()).flatMap(interfaces => interfaces?.map(info => info.address)),
+]);
+
 // Reserve a range of 16 addresses at a random offset.
 const reserveRange = async (): Promise<number[]> => {
 	let from: number;
@@ -15,24 +22,69 @@ const reserveRange = async (): Promise<number[]> => {
 	return context.reserve(...range);
 };
 
+const enum Availability {
+	AVAILABLE,
+	UNAVAILABLE,
+	UNKNOWN,
+}
+
 // Listen on the port to make sure it's available.
-const confirmAvailable = async (port: number, options?: net.ListenOptions): Promise<boolean> => new Promise((resolve, reject) => {
+const confirmAvailableForHost = async ({
+	host,
+	listenOptions,
+	port,
+	unknowable,
+}: {
+	host: string | undefined;
+	listenOptions?: net.ListenOptions;
+	port: number;
+	unknowable: boolean;
+}): Promise<Availability> => new Promise((resolve, reject) => {
 	const server = net.createServer();
 	server.unref();
 	server.on('error', (error: Error & {code: string}) => {
 		if (error.code === 'EADDRINUSE' || error.code === 'EACCESS') {
-			resolve(false);
+			resolve(Availability.UNAVAILABLE);
+		} else if (unknowable && (error.code === 'EADDRNOTAVAIL' || error.code === 'EINVAL')) { // https://github.com/sindresorhus/get-port/blob/0760c987c17581395d4e30432881dcb0ca6ca94a/index.js#L65
+			resolve(Availability.UNKNOWN); // The address itself is not available, so we can't check.
 		} else {
 			reject(error);
 		}
 	});
-	server.listen({...options, port}, () => {
+	server.listen({...listenOptions, host, port}, () => {
 		server.close(() => {
-			resolve(true);
+			resolve(Availability.AVAILABLE);
 		});
 	});
 });
 
+const confirmAvailable = async (port: number, listenOptions?: net.ListenOptions): Promise<boolean> => {
+	if (listenOptions?.host !== undefined) {
+		const available = await confirmAvailableForHost({
+			host: listenOptions.host,
+			listenOptions,
+			port,
+			unknowable: false,
+		});
+		return available === Availability.AVAILABLE;
+	}
+
+	for await (const host of localHosts) {
+		const available = await confirmAvailableForHost({
+			host,
+			listenOptions,
+			port,
+			unknowable: true,
+		});
+
+		if (available === Availability.UNAVAILABLE) {
+			return false;
+		}
+	}
+
+	return true;
+};
+
 let available: Promise<number[]> = reserveRange();
 export default async function getPort(options?: Omit<net.ListenOptions, 'port'>): Promise<number> {
 	const promise = available;

test/test.ts

@@ -1,9 +1,10 @@
 import net from 'node:net';
+import os from 'node:os';
 import {promisify} from 'node:util';
 import test from 'ava';
 import getPort from '../source/index.js';
 
-test('gets up to 16 ports in a block', async t => {
+test.serial('gets up to 16 ports in a block', async t => {
 	const first = await getPort();
 	let count = 1;
 
@@ -23,6 +24,72 @@ test('gets up to 16 ports in a block', async t => {
 	t.log({count, first, newBlock});
 });
 
+function * range(from: number, to: number) {
+	for (let i = from; i < to; i++) {
+		yield i;
+	}
+}
+
+test.serial('skips used ports', async t => {
+	const first = await getPort();
+	t.log({first});
+
+	let attempt;
+	for await (const i of range(1, 16)) {
+		attempt?.discard();
+		attempt = await t.try(async tt => {
+			const reserved = first + i;
+			tt.log({reserved});
+
+			const server = net.createServer();
+			tt.teardown(() => server.close());
+
+			const listen: (port: number) => Promise<void> = promisify(server.listen.bind(server));
+			await listen(reserved);
+
+			const port = await getPort();
+			tt.log({port});
+			tt.true(port > reserved);
+		});
+
+		if (attempt.passed) {
+			break;
+		}
+	}
+
+	attempt?.commit();
+});
+
+test.serial('fails on invalid hosts', async t => {
+	let code;
+	let host;
+	for await (const info of Object.values(os.networkInterfaces()).flatMap(interfaces => interfaces ?? [])) {
+		const server = net.createServer();
+		t.teardown(() => server.close());
+
+		const unavailable = await new Promise<{code: 'EADDRNOTAVAIL' | 'EINVAL'; host: string} | undefined>((resolve, reject) => {
+			server.on('error', (error: Error & {code: string}) => {
+				if (error.code === 'EADDRNOTAVAIL' || error.code === 'EINVAL') {
+					resolve({code: error.code, host: info.address});
+				} else {
+					reject(error);
+				}
+			});
+			server.listen({host: info.address, port: 0}, () => {
+				resolve(undefined);
+			});
+		});
+
+		if (unavailable !== undefined) {
+			({code, host} = unavailable);
+			break;
+		}
+	}
+
+	t.not(host, undefined);
+	await t.throwsAsync(getPort({host}), {code});
+});
+
 test('port can be bound', async t => {
 	const server = net.createServer();
 	t.teardown(() => server.close());