Function checkPortAvailable

browse/src/server.ts:853–872

(port: number, hostname: string = '127.0.0.1')

// in the Node.js polyfill where listen/close are async but the caller
// expects synchronous bind semantics. See: #486
function checkPortAvailable(port: number, hostname: string = '127.0.0.1'): Promise<PortCheckResult> {
  return new Promise((resolve) => {
    const srv = net.createServer();
    let settled = false;
    const finish = (result: PortCheckResult) => {
      if (settled) return;
      settled = true;
      resolve(result);
    };

    srv.once('error', (err) => finish(normalizePortError(err)));
    try {
      srv.listen(port, hostname, () => {
        srv.close(() => finish({ available: true }));
      });
    } catch (err) {
      finish(normalizePortError(err));
    }
  });
}

function isPortAvailable(port: number, hostname: string = '127.0.0.1'): Promise<boolean> {
  return checkPortAvailable(port, hostname).then((result) => result.available);