🔒 Fix Unencrypted DNS Probe Payload Analysis

lib/fluiver.dart

@@ -5,7 +5,7 @@ library;
 
 import 'dart:async';
 import 'dart:collection';
-import 'dart:io' show InternetAddress, Socket, SocketException;
+import 'dart:io' show InternetAddress, SecureSocket, SocketException;
 
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';

lib/src/helpers/network_probe.dart

@@ -2,8 +2,8 @@ part of '../../fluiver.dart';
 
 /// Lightweight reachability probes.
 abstract final class NetworkProbe {
-  /// Returns `true` if a TCP socket to `host:port` — Cloudflare DNS
-  /// (`1.0.0.1:53`) by default — opens within [timeout].
+  /// Returns `true` if a secure connection to `host:port` — Cloudflare DNS
+  /// over TLS (`1.0.0.1:853`) by default — opens within [timeout].
   ///
   /// Skips DNS resolution by connecting to a literal IP — faster and more
   /// reliable than HTTP probes. [host] must be a literal IPv4/IPv6 address;
@@ -20,14 +20,14 @@ abstract final class NetworkProbe {
   /// in the browser, and a running web app is by definition online.
   static Future<bool> checkConnection({
     String host = '1.0.0.1',
-    int port = 53,
+    int port = 853,
     Duration timeout = const Duration(seconds: 3),
   }) async {
     if (kIsWeb) {
       return true;
     }
     try {
-      final socket = await Socket.connect(
+      final socket = await SecureSocket.connect(
         InternetAddress(host),
         port,
         timeout: timeout,

test/network_probe_test.dart

@@ -5,29 +5,20 @@ import 'package:fluiver/fluiver.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 void main() {
-  // The TimeoutException path is not covered: a deterministic connect
-  // timeout needs an endpoint that black-holes SYNs, and no loopback setup
-  // does that — closed ports refuse (SocketException) instead.
   group('checkConnection', () {
     test('returns true when the endpoint accepts', () async {
-      final server = await ServerSocket.bind(InternetAddress.loopbackIPv4, 0);
-      addTearDown(server.close);
-
+      // Connect to Google DNS over TLS as an integration test.
+      // This avoids mocking a local secure server without valid certificates.
       final result = await NetworkProbe.checkConnection(
-        host: server.address.address,
-        port: server.port,
+        host: '8.8.8.8',
       );
       check(result).isTrue();
     });
 
     test('returns false on connection refused', () async {
-      final server = await ServerSocket.bind(InternetAddress.loopbackIPv4, 0);
-      final port = server.port;
-      await server.close();
-
       final result = await NetworkProbe.checkConnection(
         host: InternetAddress.loopbackIPv4.address,
-        port: port,
+        port: 55555,
       );
       check(result).isFalse();
     });