fix: race configured hosts first, scan network only as fallback, 500ms prob...

Matthias Nott

2026-04-01 058511cb668a1373059a6d6829cb1cbf3b9ef577

 lib/services/mqtt_service.dart
..
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@@ -114,40 +114,51 @@
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     final clientId = await _getClientId();
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-    // Probe all hosts in parallel to find which one responds, then connect to the winner
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-    final hosts = <String>{};
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+    // Phase 1: Race configured hosts (fast — just TLS probe, ~1s each)
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+    final hosts = <String>[];
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     if (config.localHost != null && config.localHost!.isNotEmpty) hosts.add(config.localHost!);
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-    if (_lastDiscoveredHost != null) hosts.add(_lastDiscoveredHost!);
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+    if (_lastDiscoveredHost != null && !hosts.contains(_lastDiscoveredHost)) hosts.add(_lastDiscoveredHost!);
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     if (config.vpnHost != null && config.vpnHost!.isNotEmpty) hosts.add(config.vpnHost!);
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     if (config.host.isNotEmpty) hosts.add(config.host);
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-    _mqttLog('MQTT: probing ${hosts.length} hosts in parallel: ${hosts.join(", ")}');
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-    onStatusDetail?.call('Probing ${hosts.length} hosts...');
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+    _mqttLog('MQTT: racing ${hosts.length} configured hosts: ${hosts.join(", ")}');
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+    onStatusDetail?.call('Connecting...');
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-    // Probe all configured hosts in parallel — first to respond wins
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+    // Race: first probe to succeed wins, don't wait for others
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     String? winner;
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     if (hosts.isNotEmpty) {
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-      final probes = hosts.map((h) => _probeHost(h, config.port)).toList();
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-      // Also start discovery in parallel
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-      if (_lastDiscoveredHost == null) {
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-        probes.add(() async {
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-          final discovered = await _discoverViaMdns();
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-          if (discovered != null) {
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-            _lastDiscoveredHost = discovered;
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-            return discovered;
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+      final completer = Completer<String?>();
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+      int pending = hosts.length;
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+      for (final host in hosts) {
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+        _probeHost(host, config.port).then((result) {
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+          if (result != null && !completer.isCompleted) {
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+            completer.complete(result);
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+          } else {
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+            pending--;
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+            if (pending <= 0 && !completer.isCompleted) {
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+              completer.complete(null); // All failed
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+            }
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           }
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-          return null;
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-        }());
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+        });
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       }
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-      final results = await Future.wait(probes);
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-      winner = results.firstWhere((r) => r != null, orElse: () => null);
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-    } else if (_lastDiscoveredHost == null) {
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-      // No configured hosts — try discovery only
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-      winner = await _discoverViaMdns();
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-      if (winner != null) _lastDiscoveredHost = winner;
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+      winner = await completer.future.timeout(
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+        const Duration(seconds: 3),
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+        onTimeout: () => null,
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+      );
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+    }
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+
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+    // Phase 2: If configured hosts failed, try Bonjour/subnet discovery
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+    if (winner == null && !_intentionalClose) {
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+      _mqttLog('MQTT: configured hosts failed, trying discovery...');
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+      onStatusDetail?.call('Scanning network...');
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+      final discovered = await _discoverViaMdns();
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+      if (discovered != null) {
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+        _lastDiscoveredHost = discovered;
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+        winner = discovered;
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+      }
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     }
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     if (winner != null && !_intentionalClose) {
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-      _mqttLog('MQTT: probe winner: $winner, connecting...');
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+      _mqttLog('MQTT: winner: $winner, connecting...');
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       onStatusDetail?.call('Connecting to $winner...');
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       try {
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         if (await _tryConnect(winner, clientId, timeout: 5000)) return;
..
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@@ -314,7 +325,7 @@
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       final socket = await SecureSocket.connect(
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         host,
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         port,
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-        timeout: const Duration(seconds: 1),
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+        timeout: const Duration(milliseconds: 500),
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         onBadCertificate: (_) => true, // Accept self-signed cert during scan
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       );
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       await socket.close();