khamba/dist/functions/freePort.js

A cli tool for sharing files through local network.

import { createServer } from 'net';
export const getFreePort = async () => {
    return await new Promise((resolve, reject) => {
        const server = createServer();
        let port = 0;
        server.once('listening', () => {
            const address = server.address();
            if (address == null) {
                return reject(new Error('Server was not listening'));
            }
            if (typeof address === 'string') {
                return reject(new Error('Server was Unix Socket'));
            }
            port = address.port;
            server.close();
        });
        server.once('close', () => {
            resolve(port);
        });
        server.once('error', reject);
        server.listen(0, '127.0.0.1');
    });
};