@lipemat/js-boilerplate/helpers/dev-server-port.js

Dependencies and scripts for a no config JavaScript app

import net from 'net';
/**
 * First port within the dev server range, and the default port.
 */
export const DEV_SERVER_PORT_START = 3000;
/**
 * Number of ports available to the dev server.
 *
 * Capped to the maximum number of simultaneous PHP dev servers.
 */
export const DEV_SERVER_PORT_RANGE = 20;
const DEV_SERVER_HOST = '0.0.0.0';
/**
 * Check if a single port is free to bind to.
 *
 * @param {number} port - Port to check.
 *
 * @return {Promise<boolean>}
 */
function isPortFree(port) {
    return new Promise(resolve => {
        const server = net.createServer();
        server.unref();
        server.on('error', () => {
            resolve(false);
        });
        server.listen({ host: DEV_SERVER_HOST, port }, () => {
            server.close(() => {
                resolve(true);
            });
        });
    });
}
/**
 * Resolve the first free port within the dev server range.
 *
 * @throws {Error} - When every port within the range is in use.
 *
 * @return {Promise<number>}
 */
export async function getDevServerPort() {
    const lastPort = DEV_SERVER_PORT_START + DEV_SERVER_PORT_RANGE - 1;
    for (let port = DEV_SERVER_PORT_START; port <= lastPort; port++) {
        if (await isPortFree(port)) {
            return port;
        }
    }
    throw new Error(`Unable to start the dev server: all ${DEV_SERVER_PORT_RANGE} ports (${DEV_SERVER_PORT_START}-${lastPort}) are in use.`);
}
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