Merge pull request #14 from OpenIPC/fix/onvif-discovery-android-platform-not-supported

fix(onvif): make WS-Discovery work on Android/iOS

Author: keyldev

src/OpenIPC.Viewer.Devices/Onvif/Discovery/PlatformSafeUdpClient.cs

@@ -0,0 +1,44 @@
+using System.Net;
+using System.Net.Sockets;
+using System.Threading.Tasks;
+using Onvif.Core.Discovery.Interfaces;
+
+namespace OpenIPC.Viewer.Devices.Onvif.Discovery;
+
+// Drop-in IUdpClient for Onvif.Core's WSDiscovery. The stock UdpClientWrapper
+// calls IPGlobalProperties.GetActiveTcpListeners() in its constructor (a
+// port-collision pre-check) — that API is unimplemented on Android/iOS and
+// throws PlatformNotSupportedException ("Arg_PlatformNotSupported"), so device
+// discovery died before sending a single probe on mobile.
+//
+// This implementation skips that check: it binds an ephemeral UDP socket and
+// sends the multicast probe to 239.255.255.250:3702. WS-Discovery ProbeMatch
+// replies come back as *unicast* to our source port, so we never join a
+// multicast group — which also means no Android WifiManager.MulticastLock is
+// required. Works identically on desktop, so no per-platform branching.
+internal sealed class PlatformSafeUdpClient : IUdpClient
+{
+    private readonly UdpClient _client;
+
+    public PlatformSafeUdpClient()
+    {
+        // Port 0 = let the OS pick a free ephemeral port. The stock wrapper
+        // hard-bound port 80, which is both privileged and collision-prone.
+        _client = new UdpClient(new IPEndPoint(IPAddress.Any, 0)) { EnableBroadcast = true };
+    }
+
+    public short Ttl
+    {
+        get => _client.Ttl;
+        set => _client.Ttl = value;
+    }
+
+    public Task<int> SendAsync(byte[] datagram, int bytes, IPEndPoint endPoint) =>
+        _client.SendAsync(datagram, bytes, endPoint);
+
+    public Task<UdpReceiveResult> ReceiveAsync() => _client.ReceiveAsync();
+
+    public void Close() => _client.Close();
+
+    public void Dispose() => _client.Dispose();
+}

src/OpenIPC.Viewer.Devices/Onvif/Discovery/WsDiscoveryService.cs

@@ -6,7 +6,6 @@
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
 using Onvif.Core.Discovery;
-using Onvif.Core.Discovery.Common;
 using Onvif.Core.Discovery.Models;
 using OpenIPC.Viewer.Core.Onvif.Discovery;
 
@@ -32,7 +31,9 @@ public async IAsyncEnumerable<DiscoveredCamera> ScanAsync(
     {
         var seconds = Math.Max(1, (int)Math.Ceiling(timeout.TotalSeconds));
         var ws = new WSDiscovery();
-        var client = new UdpClientWrapper();
+        // Our own IUdpClient — the stock UdpClientWrapper crashes on Android/iOS
+        // (GetActiveTcpListeners is PlatformNotSupported). See PlatformSafeUdpClient.
+        var client = new PlatformSafeUdpClient();
 
         _logger.LogDebug("WS-Discovery scan starting (timeout={Seconds}s)", seconds);
         IEnumerable<DiscoveryDevice> devices;