feat: auto-reconnect on network change (WiFi/cellular/VPN switch)

Matthias Nott

2026-04-01 3e19d6917ff245863be43a39a76daa7010ecda6f

 lib/services/mqtt_service.dart
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@@ -5,6 +5,7 @@
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 import 'package:crypto/crypto.dart';
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 import 'package:bonsoir/bonsoir.dart';
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+import 'package:connectivity_plus/connectivity_plus.dart';
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 import 'package:flutter/foundation.dart';
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 import 'package:flutter/widgets.dart';
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 import 'package:path_provider/path_provider.dart' as pp;
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@@ -50,6 +51,8 @@
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   bool _intentionalClose = false;
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   String? _clientId;
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   String? _lastDiscoveredHost;
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+  StreamSubscription? _connectivitySub;
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+  List<ConnectivityResult>? _lastConnectivity;
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   StreamSubscription? _updatesSub;
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   // Message deduplication
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@@ -103,6 +106,36 @@
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     _intentionalClose = false;
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     _setStatus(ConnectionStatus.connecting);
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+
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+    // Start listening for network changes (WiFi↔cellular, VPN connect/disconnect)
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+    _connectivitySub ??= Connectivity().onConnectivityChanged.listen((results) {
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+      if (_lastConnectivity != null && !_intentionalClose) {
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+        final changed = results.length != _lastConnectivity!.length ||
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+            !results.every((r) => _lastConnectivity!.contains(r));
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+        if (changed) {
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+          _mqttLog('MQTT: network changed: ${results.map((r) => r.name).join(",")} — forcing reconnect');
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+          // Force disconnect and reconnect on new network
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+          final client = _client;
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+          if (client != null) {
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+            _intentionalClose = true;
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+            client.autoReconnect = false;
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+            try { client.disconnect(); } catch (_) {}
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+            _client = null;
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+            _updatesSub?.cancel();
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+            _updatesSub = null;
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+            _intentionalClose = false;
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+          }
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+          _lastDiscoveredHost = null; // Clear cached discovery — subnet may have changed
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+          connectedHost = null;
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+          connectedVia = null;
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+          _setStatus(ConnectionStatus.reconnecting);
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+          Future.delayed(const Duration(milliseconds: 500), () {
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+            if (!_intentionalClose) connect();
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+          });
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+        }
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+      }
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+      _lastConnectivity = results;
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+    });
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     // Load trusted cert fingerprint for TOFU verification
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     if (_trustedFingerprint == null) await _loadTrustedFingerprint();
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@@ -724,6 +757,8 @@
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     _intentionalClose = true;
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     _updatesSub?.cancel();
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     _updatesSub = null;
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+    _connectivitySub?.cancel();
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+    _connectivitySub = null;
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     try {
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       _client?.disconnect();