Function findFreePort

scripts/dev-safe.mjs:208–226

(preferredPort, host = "127.0.0.1")

 * @returns {Promise<number>} The actual port that was acquired
 */
export async function findFreePort(preferredPort, host = "127.0.0.1") {
  // If preferredPort is 0, skip the check and go straight to OS assignment
  if (preferredPort > 0) {
    const preferredAvailable = await tryPort(preferredPort, host);
    if (preferredAvailable) {
      return preferredPort;
    }
  }

  // Fall back to OS-assigned port
  return new Promise((resolve, reject) => {
    const server = net.createServer();
    server.once("error", reject);
    server.listen(0, host, () => {
      const { port } = server.address();
      server.close(() => resolve(port));
    });
  });
}

/**
 * Check if a port is available by attempting to bind to it.