MTranServer/desktop/ports.js

import net from 'net';

export async function isPortAvailable(port, host) {
  return new Promise((resolve) => {
    const server = net.createServer();
    server.unref();
    server.once('error', () => {
      resolve(false);
    });
    server.once('listening', () => {
      server.close(() => resolve(true));
    });
    server.listen(port, host);
  });
}

export async function getFreePort() {
  return new Promise((resolve, reject) => {
    const server = net.createServer();
    server.unref();
    server.once('error', reject);
    server.listen(0, () => {
      const address = server.address();
      if (address && typeof address !== 'string') {
        const port = address.port;
        server.close(() => resolve(port));
      } else {
        reject(new Error('Failed to get port'));
      }
    });
  });
}