static Future _loopback()

in lib/http_multi_server.dart [202:231]

• 19 lines of code
• 7 McCabe index (conditional complexity)

  static Future<HttpServer> _loopback(
      int port, Future<HttpServer> Function(InternetAddress, int port) bind,
      [int remainingRetries = 5]) async {
    if (!await supportsIPv4) {
      return await bind(InternetAddress.loopbackIPv6, port);
    }

    var v4Server = await bind(InternetAddress.loopbackIPv4, port);
    if (!await supportsIPv6) return v4Server;

    try {
      // Reuse the IPv4 server's port so that if [port] is 0, both servers use
      // the same ephemeral port.
      var v6Server = await bind(InternetAddress.loopbackIPv6, v4Server.port);
      return HttpMultiServer([v4Server, v6Server]);
    } on SocketException catch (error) {
      // If there is already a server listening we'll lose the reference on a
      // rethrow.
      await v4Server.close();

      if (error.osError?.errorCode != _addressInUseErrno) rethrow;
      if (port != 0) rethrow;
      if (remainingRetries == 0) rethrow;

      // A port being available on IPv4 doesn't necessarily mean that the same
      // port is available on IPv6. If it's not (which is rare in practice),
      // we try again until we find one that's available on both.
      return await _loopback(port, bind, remainingRetries - 1);
    }
  }