From c3bbed9545ce749331b32e40ae59712266e84c1b Mon Sep 17 00:00:00 2001
From: Mihkel Eidast <mihkeleidast@gmail.com>
Date: Sun, 3 Oct 2021 19:39:27 +0300
Subject: [PATCH] Check all local hosts for port availability (#56)

---
 .github/workflows/main.yml |  8 ++++--
 index.js                   | 59 +++++++++++++++++++++++++++++++-------
 readme.md                  |  6 +++-
 test.js                    | 18 ++++++++++++
 4 files changed, 77 insertions(+), 14 deletions(-)

diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 18531b3..64fc85b 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -4,11 +4,15 @@ on:
   - pull_request
 jobs:
   test:
-    name: Node.js ${{ matrix.node-version }}
-    runs-on: ubuntu-latest
+    name: Node.js ${{ matrix.node-version }} on ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
     strategy:
       fail-fast: false
       matrix:
+        os:
+          - ubuntu-latest
+          - windows-latest
+          - macos-latest
         node-version:
           - 14
           - 12
diff --git a/index.js b/index.js
index f3e2210..73a7199 100644
--- a/index.js
+++ b/index.js
@@ -1,5 +1,6 @@
 'use strict';
 const net = require('net');
+const os = require('os');
 
 class Locked extends Error {
 	constructor(port) {
@@ -20,17 +21,51 @@ const releaseOldLockedPortsIntervalMs = 1000 * 15;
 // Lazily create interval on first use
 let interval;
 
-const getAvailablePort = options => new Promise((resolve, reject) => {
-	const server = net.createServer();
-	server.unref();
-	server.on('error', reject);
-	server.listen(options, () => {
-		const {port} = server.address();
-		server.close(() => {
-			resolve(port);
+const getLocalHosts = () => {
+	const interfaces = os.networkInterfaces();
+	// Add undefined value for createServer function to use default host,
+	// and default IPv4 host in case createServer defaults to IPv6.
+	const results = new Set([undefined, '0.0.0.0']);
+
+	for (const _interface of Object.values(interfaces)) {
+		for (const config of _interface) {
+			results.add(config.address);
+		}
+	}
+
+	return results;
+};
+
+const checkAvailablePort = options =>
+	new Promise((resolve, reject) => {
+		const server = net.createServer();
+		server.unref();
+		server.on('error', reject);
+		server.listen(options, () => {
+			const {port} = server.address();
+			server.close(() => {
+				resolve(port);
+			});
 		});
 	});
-});
+
+const getAvailablePort = async (options, hosts) => {
+	if (options.host || options.port === 0) {
+		return checkAvailablePort(options);
+	}
+
+	for (const host of hosts) {
+		try {
+			await checkAvailablePort({port: options.port, host}); // eslint-disable-line no-await-in-loop
+		} catch (error) {
+			if (!['EADDRNOTAVAIL', 'EINVAL'].includes(error.code)) {
+				throw error;
+			}
+		}
+	}
+
+	return options.port;
+};
 
 const portCheckSequence = function * (ports) {
 	if (ports) {
@@ -59,15 +94,17 @@ module.exports = async options => {
 		}
 	}
 
+	const hosts = getLocalHosts();
+
 	for (const port of portCheckSequence(ports)) {
 		try {
-			let availablePort = await getAvailablePort({...options, port}); // eslint-disable-line no-await-in-loop
+			let availablePort = await getAvailablePort({...options, port}, hosts); // eslint-disable-line no-await-in-loop
 			while (lockedPorts.old.has(availablePort) || lockedPorts.young.has(availablePort)) {
 				if (port !== 0) {
 					throw new Locked(port);
 				}
 
-				availablePort = await getAvailablePort({...options, port}); // eslint-disable-line no-await-in-loop
+				availablePort = await getAvailablePort({...options, port}, hosts); // eslint-disable-line no-await-in-loop
 			}
 
 			lockedPorts.young.add(availablePort);
diff --git a/readme.md b/readme.md
index 5c5f09c..f16fcd6 100644
--- a/readme.md
+++ b/readme.md
@@ -1,6 +1,8 @@
 # get-port
 
-> Get an available [TCP port](https://en.wikipedia.org/wiki/Port_(computer_networking))
+> Get an available [TCP port](https://en.wikipedia.org/wiki/Port_(computer_networking)).
+>
+>
 
 ## Install
 
@@ -68,6 +70,8 @@ Type: `string`
 
 The host on which port resolution should be performed. Can be either an IPv4 or IPv6 address.
 
+By default, `get-port` checks availability on all local addresses defined in [OS network interfaces](https://nodejs.org/api/os.html#os_os_networkinterfaces). If this option is set, it will only check the specified host.
+
 ### getPort.makeRange(from, to)
 
 Make a range of ports `from`...`to`.
diff --git a/test.js b/test.js
index ba4c794..59e41f1 100644
--- a/test.js
+++ b/test.js
@@ -153,3 +153,21 @@ test('ports are locked for up to 30 seconds', async t => {
 	t.is(port3, port);
 	global.setInterval = setInterval;
 });
+
+const bindPort = async ({port, host}) => {
+	const server = net.createServer();
+	await promisify(server.listen.bind(server))({port, host});
+	return server;
+};
+
+test('preferred ports is bound up with different hosts', async t => {
+	const desiredPorts = [10990, 10991, 10992, 10993];
+
+	await bindPort({port: desiredPorts[0]});
+	await bindPort({port: desiredPorts[1], host: '0.0.0.0'});
+	await bindPort({port: desiredPorts[2], host: '127.0.0.1'});
+
+	const port = await getPort({port: desiredPorts});
+
+	t.is(port, desiredPorts[3]);
+});