Bump to v3.0.1: move UPnP discovery off the UI thread (fixes hang on Andre's network)

Bug: ticking the "Automatically open my router for incoming connections
(UPnP)" box in Preferences could freeze the WinForms message pump until
Mono.Nat's NatUtility.StartDiscovery() returned. On Andre's setup it never
did — audio kept flowing (audio threads are independent of the UI thread)
but the window stopped repainting, the system-tray hotkey stopped
responding, and the only way out was Task Manager.

Pre-existing latent bug in the v2.1 UPnP code; we just shipped without
anyone exercising the path on a problematic network (multiple adapters /
VPN / SSDP-swallowing router).

Fix: three call sites moved off the UI thread via Task.Run -
  * MainForm OnShown (startup re-enable from saved AppConfig.UpnpEnabled)
  * MainForm Preferences applyUpnpEnabled callback (user ticks the box)
  * MainForm power-resume handler (Refresh() after sleep/wake)
RouterPortMapper.Start() returns "immediately" only when StartDiscovery
returns quickly; on a slow network it can block synchronously for many
seconds. Same is true of Stop()'s socket teardown and Refresh()'s
teardown-then-restart sequence. All three are now safely backgrounded.

StatusChanged is unaffected - it already fires on the mapper's own thread
and the PreferencesDialog handler BeginInvokes back to the UI thread.
Live status label updates correctly during the new background discovery.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/RemSound.App/AboutDialog.cs

@@ -20,6 +20,32 @@ internal sealed class AboutDialog : Form
     /// updates" path.</summary>
     private const string ReleaseNotes =
         """
+        RemSound v3.0.1
+
+        Hot-fix for a bug in the "Automatically open my router
+        for incoming connections (UPnP)" tickbox.
+
+        On some network setups (machines with several network
+        adapters, a VPN connected, or a router that doesn't
+        answer the way RemSound's UPnP library expects) ticking
+        that box could freeze RemSound's window — audio kept
+        flowing, but you couldn't open the window again, even
+        from the system tray. The only way out was to end the
+        process from Task Manager.
+
+        The fault was that RemSound was doing the router
+        discovery on the same thread that draws the window, so
+        a slow router (or no router answering at all) would
+        block the window until it finished — which sometimes
+        was never. v3.0.1 moves that work off to a background
+        thread so the window stays responsive while RemSound
+        looks for the router.
+
+        Nothing else has changed from v3.0 — same wire format,
+        same codec list, same everything. If you were already
+        running v3.0 happily, this update fixes a problem you
+        may not have hit; you can install it at your leisure.
+
         RemSound v3.0
 
         A big release with two things you'll actually notice:

src/RemSound.App/MainForm.cs

@@ -1051,12 +1051,22 @@ public sealed class MainForm : Form
 
             // Kick off UPnP discovery if the user has the box ticked. Off by default; the
             // mapper itself coalesces redundant Start() calls so a re-enter via Shown after
-            // a sleep cycle is harmless.
+            // a sleep cycle is harmless. Run on a thread-pool thread because
+            // NatUtility.StartDiscovery() (Mono.Nat 3.0.4) sets up SSDP sockets on every
+            // network interface and CAN BLOCK FOR TENS OF SECONDS, or indefinitely, on
+            // unusual network setups (multiple adapters, VPNs, hostile firewalls, routers
+            // that swallow SSDP). Calling it on the UI thread freezes the WinForms message
+            // pump — Andre's v3.0 hang was this exact pattern. The status label still
+            // updates correctly because StatusChanged fires on the mapper's own thread and
+            // the PreferencesDialog handler BeginInvokes back to the UI thread. 2026-05-23.
             var startupCfg = AppConfig.Load();
             if (startupCfg.UpnpEnabled)
             {
-                try { routerPortMapper.Start(); }
-                catch (Exception ex) { logFile.Event($"upnp: start failed: {ex.GetType().Name}: {ex.Message}"); }
+                Task.Run(() =>
+                {
+                    try { routerPortMapper.Start(); }
+                    catch (Exception ex) { logFile.Event($"upnp: start failed: {ex.GetType().Name}: {ex.Message}"); }
+                });
             }
 
             // Startup update check — separate from the periodic timer because users who
@@ -1751,17 +1761,28 @@ public sealed class MainForm : Form
             applyUpnpEnabled: enabled =>
             {
                 // The persist already happened in the dialog; this callback only flips the
-                // live RouterPortMapper. Start kicks off discovery; Stop politely removes any
-                // existing mapping.
+                // live RouterPortMapper. Start/Stop both run on a thread-pool thread because
+                // NatUtility's discovery + socket teardown CAN BLOCK FOR TENS OF SECONDS, or
+                // indefinitely, on unusual network setups (multiple adapters, VPNs, hostile
+                // firewalls). Doing that on the UI thread here would freeze the
+                // Preferences dialog AND every other UI element until the call returned —
+                // Andre's v3.0 hang was triggered from this exact handler. See the longer
+                // explanation on the startup-time UPnP block in OnShown. 2026-05-23.
                 if (enabled)
                 {
-                    try { routerPortMapper.Start(); }
-                    catch (Exception ex) { logFile.Event($"upnp: start from prefs failed: {ex.GetType().Name}: {ex.Message}"); }
+                    Task.Run(() =>
+                    {
+                        try { routerPortMapper.Start(); }
+                        catch (Exception ex) { logFile.Event($"upnp: start from prefs failed: {ex.GetType().Name}: {ex.Message}"); }
+                    });
                 }
                 else
                 {
-                    try { routerPortMapper.Stop(); }
-                    catch (Exception ex) { logFile.Event($"upnp: stop from prefs failed: {ex.GetType().Name}: {ex.Message}"); }
+                    Task.Run(() =>
+                    {
+                        try { routerPortMapper.Stop(); }
+                        catch (Exception ex) { logFile.Event($"upnp: stop from prefs failed: {ex.GetType().Name}: {ex.Message}"); }
+                    });
                 }
             },
             getUpnpSnapshot: () => (routerPortMapper.Status, routerPortMapper.ExternalEndpoint, routerPortMapper.LastError),
@@ -3631,11 +3652,18 @@ public sealed class MainForm : Form
 
             // Re-poke the router. UPnP/NAT-PMP mappings often survive a sleep, but cheap
             // routers and ISP-supplied combo boxes sometimes drop their NAT table — easier
-            // to just rediscover than to guess. Refresh() is a no-op if UPnP is off.
+            // to just rediscover than to guess. Refresh() is a no-op if UPnP is off. Run on
+            // a thread-pool thread for the same reason as the other UPnP entry points: the
+            // NatUtility teardown + restart inside Refresh() can block for tens of seconds
+            // on unusual networks, and we're on the UI thread during the resume handler.
+            // 2026-05-23.
             if (AppConfig.Load().UpnpEnabled)
             {
-                try { routerPortMapper.Refresh(); }
-                catch (Exception ex) { logFile.Event($"upnp: refresh-on-resume failed: {ex.GetType().Name}: {ex.Message}"); }
+                Task.Run(() =>
+                {
+                    try { routerPortMapper.Refresh(); }
+                    catch (Exception ex) { logFile.Event($"upnp: refresh-on-resume failed: {ex.GetType().Name}: {ex.Message}"); }
+                });
             }
         }
         catch (Exception ex)

src/RemSound.App/RemSound.App.csproj

@@ -14,7 +14,7 @@
          tag_name on the latest GitHub release; bump it on every public release. The
          AssemblyVersion / FileVersion default to this value, and Assembly.GetName().Version
          is what the About dialog and the updater both read. -->
-    <Version>3.0.0</Version>
+    <Version>3.0.1</Version>
   </PropertyGroup>
 
   <ItemGroup>