RawDatagramSocket 类 抽象 接口

UDP 套接字的未缓冲接口。

原始数据报套接字以与底层操作系统接收相同的数据块将 Stream 的 RawSocketEvent 传递。

注意，事件 RawSocketEvent.readClosed 永远不会收到，因为 UDP 套接字不能被远程对等方关闭。

它与 POSIX 原始套接字 不相同。

import 'dart:io';
import 'dart:typed_data';

void main() async {
  // Read the current time from an NTP server.
  final serverAddress = (await InternetAddress.lookup('pool.ntp.org')).first;
  final clientSocket = await RawDatagramSocket.bind(
      serverAddress.type == InternetAddressType.IPv6
          ? InternetAddress.anyIPv6
          : InternetAddress.anyIPv4,
      0);
  final ntpQuery = Uint8List(48);
  ntpQuery[0] = 0x23; // See RFC 5905 7.3

  clientSocket.listen((event) {
    switch (event) {
      case RawSocketEvent.read:
        final datagram = clientSocket.receive();
        // Parse `datagram.data`
        clientSocket.close();
        break;
      case RawSocketEvent.write:
        if (clientSocket.send(ntpQuery, serverAddress, 123) > 0) {
          clientSocket.writeEventsEnabled = false;
        }
        break;
      case RawSocketEvent.closed:
        break;
      default:
        throw "Unexpected event $event";
    }
  });
}