2 const net = require('net');
4 class Locked extends Error {
6 super(`${port} is locked`);
15 // On this interval, the old locked ports are discarded,
16 // the young locked ports are moved to old locked ports,
17 // and a new young set for locked ports are created.
18 const releaseOldLockedPortsIntervalMs = 1000 * 15;
20 // Lazily create interval on first use
23 const getAvailablePort = options => new Promise((resolve, reject) => {
24 const server = net.createServer();
26 server.on('error', reject);
27 server.listen(options, () => {
28 const {port} = server.address();
35 const portCheckSequence = function * (ports) {
40 yield 0; // Fall back to 0 if anything else failed
43 module.exports = async options => {
47 ports = typeof options.port === 'number' ? [options.port] : options.port;
50 if (interval === undefined) {
51 interval = setInterval(() => {
52 lockedPorts.old = lockedPorts.young;
53 lockedPorts.young = new Set();
54 }, releaseOldLockedPortsIntervalMs);
56 // Does not exist in some environments (Electron, Jest jsdom env, browser, etc).
62 for (const port of portCheckSequence(ports)) {
64 let availablePort = await getAvailablePort({...options, port}); // eslint-disable-line no-await-in-loop
65 while (lockedPorts.old.has(availablePort) || lockedPorts.young.has(availablePort)) {
67 throw new Locked(port);
70 availablePort = await getAvailablePort({...options, port}); // eslint-disable-line no-await-in-loop
73 lockedPorts.young.add(availablePort);
76 if (!['EADDRINUSE', 'EACCES'].includes(error.code) && !(error instanceof Locked)) {
82 throw new Error('No available ports found');
85 module.exports.makeRange = (from, to) => {
86 if (!Number.isInteger(from) || !Number.isInteger(to)) {
87 throw new TypeError('`from` and `to` must be integer numbers');
90 if (from < 1024 || from > 65535) {
91 throw new RangeError('`from` must be between 1024 and 65535');
94 if (to < 1024 || to > 65536) {
95 throw new RangeError('`to` must be between 1024 and 65536');
99 throw new RangeError('`to` must be greater than or equal to `from`');
102 const generator = function * (from, to) {
103 for (let port = from; port <= to; port++) {
108 return generator(from, to);