My example code below is working in Android, but in Windows it never be able to receive any message. Can anyone give me hint about what is the problem? Thanks.

Note: it is complete code in main.dart, you can copy it to your main.dart and run it. Note: originally it can't be posted to SO because of this message: "It looks like your post is mostly code; please add some more details.". So I add some more text, please ignore this second note.

import 'package:flutter/material.dart';
import 'dart:io';
import 'dart:convert';
import 'dart:async';
import 'dart:math';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key, required this.title});
  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  @override
  void initState() {
    super.initState();
    Timer(Duration(milliseconds: 0), () async {
      InternetAddress mine = await getMyIPAddress();
      startUdpReceiver(mine);
    });
  }
  
  String myIp = "";
  int myPort = 0;
  String dataReceived = "";
  startUdpReceiver(InternetAddress mine) {
    RawDatagramSocket.bind(mine.address, 0).then((RawDatagramSocket socket) {
      myIp = "${mine.address}";
      myPort = socket.port;
      setState(() { });
      socket.listen((RawSocketEvent e) {
        Datagram? d = socket.receive();
        if (d != null) {
          dataReceived = new String.fromCharCodes(d.data).trim();
          setState(() { });
          dynamic detail = {};
          try { detail = jsonDecode(dataReceived); } catch (e) {}
          if (detail["senderIp"] != null && detail["message"] == "testing") {
            sendData(detail["senderIp"], detail["senderPort"], "Message received: "+detail["message"]);
          }
        }
      });
    });
  }
  String dataSent = "";
  void sendData(String toIp, int toPort, String message) {
    RawDatagramSocket.bind(InternetAddress.anyIPv4, 0).then((RawDatagramSocket socket){
      String data = jsonEncode({"senderIp":myIp,"senderPort":myPort,"message":message});
      dataSent = "to $toIp:$toPort: "+data;
      setState(() { });
      socket.send(utf8.encode(data), InternetAddress(toIp), toPort);
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text("My address: $myIp:$myPort"),
            Text("Data sent: $dataSent"),
            Text("Data received: $dataReceived"),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () async {
          String txt = await gettext(context, "IP:Port");
          if (txt != "") {
            String toIp = txt.split(":").first;
            String toPort = txt.split(":").last;
            sendData(toIp, int.parse(toPort), "testing");
          }
        },
        tooltip: 'Send',
        child: const Icon(Icons.send),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}

Future<InternetAddress> getMyIPAddress() async {
  //not mine, copied from SO
  InternetAddress result;

  int code = Random().nextInt(255);
  var dgSocket = await RawDatagramSocket.bind(InternetAddress.anyIPv4, 0);
  dgSocket.readEventsEnabled = true;
  dgSocket.broadcastEnabled = true;
  Future<InternetAddress> ret =
      dgSocket.timeout(Duration(milliseconds: 100), onTimeout: (sink) {
    sink.close();
  }).expand<InternetAddress>((event) {
    if (event == RawSocketEvent.read) {
      Datagram? dg = dgSocket.receive();
      if (dg != null && dg.data.length == 1 && dg.data[0] == code) {
        dgSocket.close();
        return [dg.address];
      }
    }
    return [];
  }).firstWhere((InternetAddress a) => a != null);

  dgSocket.send([code], InternetAddress("255.255.255.255"), dgSocket.port);
  return ret;
}  

Future<String> gettext(BuildContext context, String message) async {
  //not mine, copied from SO
  String tex = '';
  bool ok = false;
  await showDialog(
    context: context,
    builder: (context) {
      return AlertDialog(
        content: Column(
          mainAxisSize: MainAxisSize.min,
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            Text(message),
            TextField(
                onChanged: (value) {
                  tex = value;
                }),
          ],
        ),
        actions: [
          ElevatedButton(
            child: Text("OK"),
            onPressed: () {
              ok = true;
              Navigator.pop(context);
            }
          ),
          ElevatedButton(
            child: Text("Cancel"),
            onPressed: () {
              Navigator.pop(context);
            }
          ),
        ],
      );
    },
  );
  return tex;
}