RawDatagramSocket class

An unbuffered interface to a UDP socket.

The raw datagram socket delivers a Stream of RawSocketEvents in the same chunks as the underlying operating system receives them.

Note that the event RawSocketEvent.readClosed will never be received as an UDP socket cannot be closed by a remote peer.

It is not the same as a POSIX raw socket.

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";
    }
  });
}