Restore 255.255.255.255 discovery for Linux

Actually, this address should be removed because we cannot enforce the listening interface with this address at all. However, it seems that all the clients are not yet ready for this change. For now, restore the ability to respond auto discovery message with 255.255.255.255, and perhaps remove it later when clients are ready for the change.

Signed-off-by: gnattu <gnattuoc@me.com>

src/Jellyfin.Networking/AutoDiscoveryHost.cs

@@ -110,7 +110,7 @@ public sealed class AutoDiscoveryHost : BackgroundService
                     var text = Encoding.UTF8.GetString(result.Buffer);
                     if (text.Contains("who is JellyfinServer?", StringComparison.OrdinalIgnoreCase))
                     {
-                        await RespondToV2Message(respondAddress, result.RemoteEndPoint, cancellationToken).ConfigureAwait(false);
+                        await RespondToV2Message(respondAddress, result.RemoteEndPoint, udpClient, cancellationToken).ConfigureAwait(false);
                     }
                 }
                 catch (SocketException ex)
@@ -130,7 +130,7 @@ public sealed class AutoDiscoveryHost : BackgroundService
         }
     }
 
-    private async Task RespondToV2Message(IPAddress responderIp, IPEndPoint endpoint, CancellationToken cancellationToken)
+    private async Task RespondToV2Message(IPAddress responderIp, IPEndPoint endpoint, UdpClient broadCastUdpClient, CancellationToken cancellationToken)
     {
         var localUrl = _appHost.GetSmartApiUrl(endpoint.Address);
         if (string.IsNullOrEmpty(localUrl))
@@ -141,17 +141,34 @@ public sealed class AutoDiscoveryHost : BackgroundService
 
         var response = new ServerDiscoveryInfo(localUrl, _appHost.SystemId, _appHost.FriendlyName);
 
-        using var responder = new UdpClient(new IPEndPoint(responderIp, PortNumber));
-        try
+        if (Equals(responderIp, IPAddress.Broadcast))
         {
-            _logger.LogDebug("Sending AutoDiscovery response");
-            await responder
-                .SendAsync(JsonSerializer.SerializeToUtf8Bytes(response).AsMemory(), endpoint, cancellationToken)
-                .ConfigureAwait(false);
+            try
+            {
+                _logger.LogDebug("Sending AutoDiscovery response");
+                await broadCastUdpClient
+                    .SendAsync(JsonSerializer.SerializeToUtf8Bytes(response).AsMemory(), endpoint, cancellationToken)
+                    .ConfigureAwait(false);
+            }
+            catch (SocketException ex)
+            {
+                _logger.LogError(ex, "Error sending response message");
+            }
         }
-        catch (SocketException ex)
+        else
         {
-            _logger.LogError(ex, "Error sending response message");
+            using var responder = new UdpClient(new IPEndPoint(responderIp, PortNumber));
+            try
+            {
+                _logger.LogDebug("Sending AutoDiscovery response");
+                await responder
+                    .SendAsync(JsonSerializer.SerializeToUtf8Bytes(response).AsMemory(), endpoint, cancellationToken)
+                    .ConfigureAwait(false);
+            }
+            catch (SocketException ex)
+            {
+                _logger.LogError(ex, "Error sending response message");
+            }
         }
     }
 }