Add LAN-reachable mode to control surface and OSC bridge

When the new ControlSurfaceLanReachable preference is on, both the REST/WebSocket control surface and the OSC bridge bind to all interfaces (http://+:port/ via HttpListener wildcard, IPAddress.Any for OSC) instead of loopback. The settings VM persists the toggle, restarts both surfaces when flipped, and surfaces a ControlSurfaceUrl computed from the first non-loopback IPv4 + a Copy button so operators can paste the URL onto a control PC.

Use case: a headless host PC runs Teams + TeamsISO; a thin client on the same LAN drives it via /ui or a Stream Deck. Closed-network deployment, no auth — documented as a trusted-LAN-only mode in docs/CONTROL-SURFACE.md, including the one-time 'netsh http add urlacl url=http://+:9755/ user=Everyone' requirement and the firewall rule.

docs/CONTROL-SURFACE.md

@@ -9,18 +9,42 @@ node-RED flows, command-line scripts) can drive it without a UI binding.
 1. Open TeamsISO → Settings → DISPLAY tab.
 2. Tick "Control surface (Stream Deck / Companion)".
 3. Default port is **9755**; change it via the port textbox if needed.
-4. The server binds to `127.0.0.1` only — it is NOT reachable from the LAN.
+4. By default the server binds to `127.0.0.1` only — it is NOT reachable
-   If you need LAN access (e.g. a Stream Deck on a separate control PC),
+   from the LAN.
-   front it with `ssh -L 9755:127.0.0.1:9755` or a localhost TCP bridge.
+5. To allow other machines on the same network to drive TeamsISO (the
+   "headless host PC + thin client" scenario), tick the nested
+   "LAN-reachable" checkbox underneath. The settings panel will display
+   the LAN URL (e.g. `http://192.168.1.42:9755/ui`) with a Copy button.
 
 When enabled, the toast confirms `Control surface listening on
-http://127.0.0.1:9755/`.
+http://127.0.0.1:9755/` (or the all-interfaces equivalent in LAN mode).
+
+### One-time setup for LAN-reachable mode
+
+Windows requires elevated permission to bind a non-loopback HTTP listener.
+If you turn on LAN-reachable mode and don't see a connection from another
+machine, run this **once** in an Administrator PowerShell (replace `9755`
+if you've changed the port):
+
+```powershell
+netsh http add urlacl url=http://+:9755/ user=Everyone
+```
+
+Also confirm the Windows Firewall is letting inbound traffic to that port
+through — `New-NetFirewallRule -DisplayName "TeamsISO Control Surface" -Direction Inbound -Protocol TCP -LocalPort 9755 -Action Allow`
+in an elevated PowerShell, or add it through Windows Defender Firewall →
+Advanced Settings → Inbound Rules.
 
 ## Authentication
 
-None. The localhost-only bind is the security model. Any process on the
+None — by design. In localhost-only mode, the loopback bind is the
-operator's machine can hit these endpoints, which is the same threat model
+security model: any process on the operator's machine can hit these
-as a Stream Deck's USB connection.
+endpoints, the same threat model as a Stream Deck's USB connection.
+
+In LAN-reachable mode, the assumption is a closed/trusted network (a
+production-control LAN, a dedicated show subnet, a private vlan). Any
+machine that can route to the host on the listener port can drive
+TeamsISO. **Do not enable LAN-reachable mode on an untrusted network.**
 
 ## Response shape
 
@@ -222,7 +246,9 @@ Client→server messages are ignored for v1 — all commands go through REST.
 
 Same command surface, different transport. Enable the OSC bridge in the
 DISPLAY tab (default port **9000** — TouchOSC's default). Bound to
-`127.0.0.1` only.
+`127.0.0.1` by default; honors the same LAN-reachable toggle as the REST
+surface — when LAN mode is on, OSC binds to `0.0.0.0` so a TouchOSC tablet
+on the same network can talk to the host directly.
 
 Address vocabulary:
 
@@ -266,11 +292,7 @@ on the appropriate endpoint above.
 
 ## Future work
 
-- **OSC bridge** over UDP 9000 with `/teamsiso/iso {id} {0|1}` etc. — same
+- **HTTPS / token auth** — for deployments that don't have a closed
-  command surface, different transport. Adapter sits in front of the REST
+  network, layer TLS termination + a shared bearer token in front of the
-  handlers.
+  HttpListener. Out of scope for v1; the LAN-reachable mode is a
-- **Bidirectional state** via WebSocket — push `participants` updates so
+  trusted-network feature only.
-  controllers can light a button when an ISO is live without polling.
-- **REST apply-preset** — duplicate the dialog's apply logic into
-  `IIsoController.ApplyPreset(name)` so the `/presets/{name}/apply`
-  endpoint becomes a real action.

src/TeamsISO.App/MainWindow.xaml

@@ -1235,9 +1235,34 @@
 
                                 <Separator Margin="0,16,0,8"/>
 
-                                <CheckBox Content="Control surface (Stream Deck / Companion)"
+                                <CheckBox Content="Control surface (Stream Deck / Companion / web)"
                                           IsChecked="{Binding Settings.ControlSurfaceEnabled}"
-                                          ToolTip="Start a localhost-only HTTP server so external controllers (Bitfocus Companion, Stream Deck plugins, Bome MIDI Translator) can drive TeamsISO. Bound to 127.0.0.1; not reachable from LAN."/>
+                                          ToolTip="Start an HTTP server so external controllers (Bitfocus Companion, Stream Deck plugins, Bome MIDI Translator) or a thin-client browser can drive TeamsISO."/>
+
+                                <CheckBox Content="LAN-reachable (allow other machines on your network)"
+                                          IsChecked="{Binding Settings.ControlSurfaceLanReachable}"
+                                          Margin="20,4,0,0"
+                                          ToolTip="When checked, the control surface binds to all interfaces (0.0.0.0) instead of 127.0.0.1, so a phone or laptop on your LAN can drive TeamsISO. First time you turn this on, run this in an Administrator PowerShell once: netsh http add urlacl url=http://+:9755/ user=Everyone"/>
+
+                                <Grid Margin="20,4,0,0">
+                                    <Grid.ColumnDefinitions>
+                                        <ColumnDefinition Width="*"/>
+                                        <ColumnDefinition Width="Auto"/>
+                                    </Grid.ColumnDefinitions>
+                                    <TextBlock Grid.Column="0"
+                                               Text="{Binding Settings.ControlSurfaceUrl}"
+                                               Style="{StaticResource Wd.Text.Mono}"
+                                               FontSize="11"
+                                               Foreground="{DynamicResource Wd.Accent.Cyan}"
+                                               VerticalAlignment="Center"/>
+                                    <Button Grid.Column="1"
+                                            Style="{StaticResource Wd.Button.Ghost}"
+                                            Content="Copy"
+                                            Command="{Binding Settings.CopyControlSurfaceUrlCommand}"
+                                            Padding="10,2"
+                                            FontSize="11"
+                                            ToolTip="Copy this URL to the clipboard so you can paste it into a phone browser or controller."/>
+                                </Grid>
                                 <Grid Margin="0,8,0,0">
                                     <Grid.ColumnDefinitions>
                                         <ColumnDefinition Width="Auto"/>

src/TeamsISO.App/Services/ControlSurfaceServer.cs

@@ -59,6 +59,8 @@ public sealed class ControlSurfaceServer : IAsyncDisposable
 
     public bool IsRunning { get; private set; }
     public int Port { get; private set; } = DefaultPort;
+    /// <summary>True when the listener is bound to all interfaces (LAN-reachable) rather than just 127.0.0.1.</summary>
+    public bool BoundToLan { get; private set; }
 
     /// <summary>
     /// JSON serializer options shared across all responses. Camel-case property
@@ -81,24 +83,45 @@ public sealed class ControlSurfaceServer : IAsyncDisposable
     }
 
     /// <summary>
-    /// Start listening on the given port. Idempotent: if already running on a
+    /// Start listening on the given port. Idempotent: if already running on the
-    /// different port, stop + restart on the new one.
+    /// same (port, bindToLan) combination, no-op; otherwise stop + restart.
     /// </summary>
-    public void Start(int port)
+    /// <param name="port">TCP port to listen on.</param>
+    /// <param name="bindToLan">
+    /// When true, binds to all interfaces (<c>http://+:port/</c>) so other
+    /// machines on the LAN can reach the control surface — typical for
+    /// "headless show machine + thin client controller" setups. When false
+    /// (default), binds to <c>127.0.0.1</c> only.
+    ///
+    /// LAN binding requires either running TeamsISO as Administrator OR a
+    /// one-time URL ACL reservation at the OS level:
+    /// <code>netsh http add urlacl url=http://+:9755/ user=Everyone</code>
+    /// If neither is in place the listener throws AccessDeniedException
+    /// which we catch and surface as a logger warning.
+    /// </summary>
+    public void Start(int port, bool bindToLan = false)
     {
-        if (IsRunning && Port == port) return;
+        if (IsRunning && Port == port && BoundToLan == bindToLan) return;
         Stop();
 
         Port = port;
+        BoundToLan = bindToLan;
         _listener = new HttpListener();
-        _listener.Prefixes.Add($"http://127.0.0.1:{port}/");
+        var prefix = bindToLan
+            ? $"http://+:{port}/"
+            : $"http://127.0.0.1:{port}/";
+        _listener.Prefixes.Add(prefix);
         try
         {
             _listener.Start();
         }
         catch (HttpListenerException ex)
         {
-            _logger?.LogWarning(ex, "Could not start control surface on port {Port}.", port);
+            _logger?.LogWarning(ex,
+                "Could not start control surface on {Prefix}. " +
+                "If binding to LAN, run as Administrator once OR run: " +
+                "netsh http add urlacl url=http://+:{Port}/ user=Everyone",
+                prefix, port);
             _listener = null;
             return;
         }
@@ -122,7 +145,7 @@ public sealed class ControlSurfaceServer : IAsyncDisposable
         }
 
         IsRunning = true;
-        _logger?.LogInformation("Control surface listening on http://127.0.0.1:{Port}/ (REST + ws)", port);
+        _logger?.LogInformation("Control surface listening on {Prefix} (REST + ws)", prefix);
     }
 
     public void Stop()

src/TeamsISO.App/Services/OscBridge.cs

@@ -48,6 +48,8 @@ public sealed class OscBridge : IAsyncDisposable
 
     public bool IsRunning { get; private set; }
     public int Port { get; private set; } = DefaultPort;
+    /// <summary>True when the listener is bound to all interfaces rather than just loopback.</summary>
+    public bool BoundToLan { get; private set; }
 
     public OscBridge(
         IIsoController controller,
@@ -59,27 +61,35 @@ public sealed class OscBridge : IAsyncDisposable
         _logger = logger;
     }
 
-    public void Start(int port)
+    /// <summary>
+    /// Start the OSC listener on the given UDP port. <paramref name="bindToLan"/>
+    /// flag selects between loopback (default — only this machine) and any-
+    /// interface binding (LAN-reachable, for thin-client controllers).
+    /// Unlike the REST surface, UDP doesn't need a URL ACL — binding 0.0.0.0
+    /// is just an unprivileged port reservation.
+    /// </summary>
+    public void Start(int port, bool bindToLan = false)
     {
-        if (IsRunning && Port == port) return;
+        if (IsRunning && Port == port && BoundToLan == bindToLan) return;
         Stop();
 
         Port = port;
+        BoundToLan = bindToLan;
+        var bindAddr = bindToLan ? IPAddress.Any : IPAddress.Loopback;
         try
         {
-            // Bind to loopback only — same threat model as the REST surface.
+            _udp = new UdpClient(new IPEndPoint(bindAddr, port));
-            _udp = new UdpClient(new IPEndPoint(IPAddress.Loopback, port));
         }
         catch (SocketException ex)
         {
-            _logger?.LogWarning(ex, "Could not bind OSC bridge to udp://127.0.0.1:{Port}.", port);
+            _logger?.LogWarning(ex, "Could not bind OSC bridge to udp://{Addr}:{Port}.", bindAddr, port);
             _udp = null;
             return;
         }
         _cts = new CancellationTokenSource();
         _receiveTask = Task.Run(() => ReceiveLoopAsync(_cts.Token));
         IsRunning = true;
-        _logger?.LogInformation("OSC bridge listening on udp://127.0.0.1:{Port}/", port);
+        _logger?.LogInformation("OSC bridge listening on udp://{Addr}:{Port}/", bindAddr, port);
     }
 
     public void Stop()

src/TeamsISO.App/Services/UIPreferences.cs

@@ -38,7 +38,8 @@ public static class UIPreferences
         bool HideLocalSelf = true,
         bool AutoDisableOnDeparture = false,
         SortMode ParticipantSort = SortMode.JoinOrder,
-        bool MinimizeToTray = false);
+        bool MinimizeToTray = false,
+        bool ControlSurfaceLanReachable = false);
 
     public static Prefs Load()
     {

src/TeamsISO.App/ViewModels/GlobalSettingsViewModel.cs

@@ -33,6 +33,7 @@ public sealed class GlobalSettingsViewModel : ObservableObject
     private string _outputNameTemplate = TeamsISO.App.Services.OutputNameTemplate.Get();
     private UIPreferences.SortMode _participantSort = UIPreferences.SortMode.JoinOrder;
     private bool _minimizeToTray;
+    private bool _controlSurfaceLanReachable;
 
     public GlobalSettingsViewModel(IIsoController controller, ToastViewModel? toast = null)
     {
@@ -57,6 +58,7 @@ public sealed class GlobalSettingsViewModel : ObservableObject
         _autoDisableOnDeparture = uiPrefs.AutoDisableOnDeparture;
         _participantSort = uiPrefs.ParticipantSort;
         _minimizeToTray = uiPrefs.MinimizeToTray;
+        _controlSurfaceLanReachable = uiPrefs.ControlSurfaceLanReachable;
 
         // Bring the auto-apply flag in from the presets store so the checkbox
         // reflects the user's prior choice when the settings panel opens.
@@ -77,6 +79,18 @@ public sealed class GlobalSettingsViewModel : ObservableObject
         ApplyCommand = new AsyncRelayCommand(ApplyAsync);
         ApplyTranscoderTopologyCommand = new AsyncRelayCommand(ApplyTranscoderTopologyAsync);
         ResetOutputDefaultsCommand = new RelayCommand(ResetOutputDefaults);
+        CopyControlSurfaceUrlCommand = new RelayCommand(() =>
+        {
+            try
+            {
+                System.Windows.Clipboard.SetText(ControlSurfaceUrl);
+                _toast?.Show($"Copied: {ControlSurfaceUrl}");
+            }
+            catch
+            {
+                // Clipboard occasionally errors when something else has it locked.
+            }
+        });
     }
 
     private void ResetOutputDefaults()
@@ -207,7 +221,8 @@ public sealed class GlobalSettingsViewModel : ObservableObject
             HideLocalSelf: _hideLocalSelf,
             AutoDisableOnDeparture: _autoDisableOnDeparture,
             ParticipantSort: _participantSort,
-            MinimizeToTray: _minimizeToTray));
+            MinimizeToTray: _minimizeToTray,
+            ControlSurfaceLanReachable: _controlSurfaceLanReachable));
 
     /// <summary>
     /// Record each newly-enabled ISO's normalized output to disk under
@@ -246,9 +261,9 @@ public sealed class GlobalSettingsViewModel : ObservableObject
     }
 
     /// <summary>
-    /// REST control surface (localhost:port) — Stream Deck / Companion / OSC bridges
+    /// REST control surface — Stream Deck / Companion / thin-client controllers.
-    /// can hit it. Off by default; bound to 127.0.0.1 so LAN access requires explicit
+    /// Off by default. Bind address depends on <see cref="ControlSurfaceLanReachable"/>:
-    /// reconfiguration. Toggling reaches into App's owned ControlSurfaceServer.
+    /// loopback (127.0.0.1) by default, or all-interfaces when LAN-reachable.
     /// </summary>
     public bool ControlSurfaceEnabled
     {
@@ -258,10 +273,10 @@ public sealed class GlobalSettingsViewModel : ObservableObject
             if (!SetField(ref _controlSurfaceEnabled, value)) return;
             var srv = (Application.Current as App)?.ControlSurface;
             if (srv is null) return;
-            if (value) srv.Start(_controlSurfacePort);
+            if (value) srv.Start(_controlSurfacePort, _controlSurfaceLanReachable);
             else srv.Stop();
             _toast?.Show(value
-                ? $"Control surface listening on http://127.0.0.1:{_controlSurfacePort}/"
+                ? $"Control surface listening on {ControlSurfaceUrl}"
                 : "Control surface stopped");
         }
     }
@@ -276,13 +291,88 @@ public sealed class GlobalSettingsViewModel : ObservableObject
         set
         {
             if (!SetField(ref _controlSurfacePort, value)) return;
+            OnPropertyChanged(nameof(ControlSurfaceUrl));
             if (!_controlSurfaceEnabled) return;
             var srv = (Application.Current as App)?.ControlSurface;
-            srv?.Start(value); // Start is idempotent + handles port change
+            srv?.Start(value, _controlSurfaceLanReachable);
-            _toast?.Show($"Control surface restarted on http://127.0.0.1:{value}/");
+            _toast?.Show($"Control surface restarted on {ControlSurfaceUrl}");
         }
     }
 
+    /// <summary>
+    /// LAN-reachable mode. When false (default), control surface binds to
+    /// 127.0.0.1 — only this machine. When true, binds to all interfaces so
+    /// a thin-client controller on a phone or another laptop can drive
+    /// TeamsISO. The OSC bridge follows suit if it's running.
+    ///
+    /// Important: HttpListener requires either Administrator privilege OR a
+    /// one-time URL ACL reservation for non-loopback prefixes:
+    /// <code>netsh http add urlacl url=http://+:9755/ user=Everyone</code>
+    /// (run from an elevated PowerShell). Without that the listener throws
+    /// AccessDeniedException on Start; the failure surfaces as a logger
+    /// warning with the exact netsh command.
+    /// </summary>
+    public bool ControlSurfaceLanReachable
+    {
+        get => _controlSurfaceLanReachable;
+        set
+        {
+            if (!SetField(ref _controlSurfaceLanReachable, value)) return;
+            PersistUiPrefs();
+            OnPropertyChanged(nameof(ControlSurfaceUrl));
+            if (!_controlSurfaceEnabled) return;
+            var srv = (Application.Current as App)?.ControlSurface;
+            srv?.Start(_controlSurfacePort, value);
+            var osc = (Application.Current as App)?.OscBridge;
+            if (osc?.IsRunning == true) osc.Start(_oscBridgePort, value);
+            _toast?.Show(value
+                ? $"Control surface now LAN-reachable: {ControlSurfaceUrl}"
+                : "Control surface now loopback-only");
+        }
+    }
+
+    /// <summary>
+    /// Friendly URL of the running surface, for the settings panel + status
+    /// bar tooltip. Resolves to the first non-loopback IPv4 address when
+    /// LAN-reachable; loopback otherwise. Computed on demand because the
+    /// LAN IP may change between settings opens (Wi-Fi swap, VPN connect).
+    /// </summary>
+    public string ControlSurfaceUrl
+    {
+        get
+        {
+            var host = _controlSurfaceLanReachable
+                ? GetLanIPv4() ?? "127.0.0.1"
+                : "127.0.0.1";
+            return $"http://{host}:{_controlSurfacePort}/ui";
+        }
+    }
+
+    /// <summary>
+    /// Best-effort first IPv4 address that isn't loopback. Returns null if
+    /// no LAN interface is up. The first hit is good enough for the URL —
+    /// operators with multi-NIC setups can manually substitute.
+    /// </summary>
+    private static string? GetLanIPv4()
+    {
+        try
+        {
+            foreach (var ni in System.Net.NetworkInformation.NetworkInterface.GetAllNetworkInterfaces())
+            {
+                if (ni.OperationalStatus != System.Net.NetworkInformation.OperationalStatus.Up) continue;
+                if (ni.NetworkInterfaceType == System.Net.NetworkInformation.NetworkInterfaceType.Loopback) continue;
+                foreach (var ua in ni.GetIPProperties().UnicastAddresses)
+                {
+                    if (ua.Address.AddressFamily == System.Net.Sockets.AddressFamily.InterNetwork
+                        && !System.Net.IPAddress.IsLoopback(ua.Address))
+                        return ua.Address.ToString();
+                }
+            }
+        }
+        catch { /* best-effort */ }
+        return null;
+    }
+
     /// <summary>
     /// OSC bridge over UDP — same command surface as the REST endpoints,
     /// reachable from Companion / TouchOSC / lighting consoles. Off by default;
@@ -296,10 +386,11 @@ public sealed class GlobalSettingsViewModel : ObservableObject
             if (!SetField(ref _oscBridgeEnabled, value)) return;
             var bridge = (Application.Current as App)?.OscBridge;
             if (bridge is null) return;
-            if (value) bridge.Start(_oscBridgePort);
+            if (value) bridge.Start(_oscBridgePort, _controlSurfaceLanReachable);
             else bridge.Stop();
+            var host = _controlSurfaceLanReachable ? "0.0.0.0" : "127.0.0.1";
             _toast?.Show(value
-                ? $"OSC bridge listening on udp://127.0.0.1:{_oscBridgePort}/"
+                ? $"OSC bridge listening on udp://{host}:{_oscBridgePort}/"
                 : "OSC bridge stopped");
         }
     }
@@ -313,8 +404,9 @@ public sealed class GlobalSettingsViewModel : ObservableObject
             if (!SetField(ref _oscBridgePort, value)) return;
             if (!_oscBridgeEnabled) return;
             var bridge = (Application.Current as App)?.OscBridge;
-            bridge?.Start(value);
+            bridge?.Start(value, _controlSurfaceLanReachable);
-            _toast?.Show($"OSC bridge restarted on udp://127.0.0.1:{value}/");
+            var host = _controlSurfaceLanReachable ? "0.0.0.0" : "127.0.0.1";
+            _toast?.Show($"OSC bridge restarted on udp://{host}:{value}/");
         }
     }
 
@@ -381,6 +473,13 @@ public sealed class GlobalSettingsViewModel : ObservableObject
 
     public AsyncRelayCommand ApplyCommand { get; }
 
+    /// <summary>
+    /// Copy the current control-surface URL to the clipboard. Operators on a
+    /// thin-client setup tap this, then paste into a phone browser. Bound to
+    /// a small button next to the LAN-reachable toggle.
+    /// </summary>
+    public RelayCommand CopyControlSurfaceUrlCommand { get; }
+
     /// <summary>
     /// Restore Output settings (framerate, resolution, aspect, audio) to the engine's
     /// shipping defaults. Doesn't touch NDI groups (those are intentionally sticky —