Support array of preferred ports

.travis.yml

@@ -2,4 +2,3 @@ language: node_js
 node_js:
   - '8'
   - '6'
-  - '4'

index.js

@@ -1,6 +1,18 @@
 'use strict';
 const net = require('net');
 
+const isAvailable = 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 getPort = options => new Promise((resolve, reject) => {
 	// For backwards compatibility with number-only input
 	// TODO: Remove this in the next major version
@@ -10,19 +22,43 @@ const getPort = options => new Promise((resolve, reject) => {
 		};
 	}
 
-	const server = net.createServer();
-
-	server.unref();
-	server.on('error', reject);
-
-	server.listen(options, () => {
-		const port = server.address().port;
-		server.close(() => {
-			resolve(port);
-		});
-	});
+	if (Array.isArray(options.port)) {
+		options.port.reduce((seq, port) => {
+			return seq.catch(() => {
+				const input = getOptions(port, options.host);
+				return isAvailable(input)
+					.then(port => {
+						return port;
+					})
+					.catch(() => {
+						return new Promise((resolve, reject) => reject());
+					});
+			});
+		}, Promise.reject())
+			.then(port => resolve(port))
+			.catch(() => reject());
+	} else {
+		isAvailable(options)
+			.then(port => resolve(port))
+			.catch(() => reject());
+	}
 });
 
+function getOptions(portnumber, hostname) {
+	let options;
+	if (hostname === undefined) {
+		options = {
+			port: portnumber
+		};
+	} else {
+		options = {
+			port: portnumber,
+			host: hostname
+		};
+	}
+	return options;
+}
+
 module.exports = options => options ?
 	getPort(options).catch(() => getPort(0)) :
 	getPort(0);

readme.md

@@ -21,7 +21,7 @@ getPort().then(port => {
 });
 ```
 
-Optionally, pass in a preferred port:
+To pass in a preferred port:
 
 ```js
 getPort({port: 3000}).then(port => {
@@ -30,6 +30,14 @@ getPort({port: 3000}).then(port => {
 });
 ```
 
+To pass in an array of preferred ports:
+
+```js
+getPort({port: [3000, 3001, 3002]}).then(port => {
+	console.log(port);
+	// Will use any element in the preferred ports array if available, otherwise fall back to a random port
+});
+```
 
 ## API
 
@@ -43,9 +51,9 @@ Type: `Object`
 
 ##### port
 
-Type: `number`
+Type: `number` or `Array`
 
-The preferred port to use.
+A preferred port or an array of preferred ports to use.
 
 ##### host
 

test.js

@@ -54,3 +54,44 @@ test('preferred port given IPv4 host', async t => {
 
 	t.is(port, desiredPort);
 });
+
+test('preferred ports', async t => {
+	const desiredPorts = [9910, 9912, 9913];
+	const port = await m({
+		port: desiredPorts,
+		host: '0.0.0.0'
+	});
+
+	t.is(port, desiredPorts[0]);
+});
+
+test('first port in preferred ports array is unavailable', async t => {
+	const desiredPorts = [9090, 9091];
+
+	const server = net.createServer();
+	await pify(server.listen.bind(server))(desiredPorts[0]);
+
+	const port = await m({
+		port: desiredPorts
+	});
+
+	t.is(port, desiredPorts[1]);
+});
+
+test('all preferred ports in array are unavailable', async t => {
+	const desiredPorts = [9990, 9991];
+
+	const server1 = net.createServer();
+	await pify(server1.listen.bind(server1))(desiredPorts[0]);
+	const server2 = net.createServer();
+	await pify(server2.listen.bind(server2))(desiredPorts[1]);
+
+	const port = await m({
+		port: desiredPorts
+	});
+
+	t.is(typeof port, 'number');
+	t.true(port > 0 && port < 65536);
+	t.not(port, desiredPorts[0]);
+	t.not(port, desiredPorts[1]);
+});