Function findAvailablePort

lib/cli.js:389–422

* Find an available TCP port starting from `start`. * Tries by actually binding a socket (most reliable cross-platform approach).

(start = 8888, maxAttempts = 20)

 * Tries by actually binding a socket (most reliable cross-platform approach).
 */
function findAvailablePort(start = 8888, maxAttempts = 20) {
  for (let port = start; port < start + maxAttempts; port++) {
    try {
      const server = createServer();
      // Use a synchronous-like approach: try to listen, then close immediately
      const result = new Promise((resolve, reject) => {
        server.once('error', reject);
        server.listen(port, '127.0.0.1', () => {
          server.close(() => resolve(port));
        });
      });
      // We cannot await here (sync context), so use the blocking approach:
      // Try to bind synchronously using a different technique.
      server.close();
    } catch {
      // fall through
    }
  }
  // Synchronous fallback: try to connect; if connection refused, port is free.
  for (let port = start; port < start + maxAttempts; port++) {
    try {
      execFileSync(process.execPath, [
        '-e',
        `const s=require("net").createServer();` +
        `s.listen(${port},"127.0.0.1",()=>{s.close();process.exit(0)});` +
        `s.on("error",()=>process.exit(1))`,
      ], { timeout: 3000, stdio: 'pipe' });
      return port;
    } catch {
      continue;
    }
  }
  die(`No available ports found in range ${start}-${start + maxAttempts - 1}`);
}

// ---------------------------------------------------------------------------
// PID file management