Implement desktop sync protocol handling

WirelessTextSyncer.Windows/Services/WebSocketServerService.cs

@@ -8,8 +8,14 @@ namespace WirelessTextSyncer.Windows.Services;
 
 public sealed class WebSocketServerService : IDisposable
 {
+    private static readonly JsonSerializerOptions JsonOptions = new(JsonSerializerDefaults.Web)
+    {
+        PropertyNameCaseInsensitive = true
+    };
+
     private readonly SyncMessageHandler messageHandler;
     private readonly List<IWebSocketConnection> clients = [];
+    private readonly object clientsLock = new();
     private WebSocketServer? server;
 
     public WebSocketServerService(SyncMessageHandler messageHandler)
@@ -21,7 +27,16 @@ public sealed class WebSocketServerService : IDisposable
 
     public string LocalIpAddress { get; private set; } = "127.0.0.1";
 
-    public bool HasClient => clients.Count > 0;
+    public bool HasClient
+    {
+        get
+        {
+            lock (clientsLock)
+            {
+                return clients.Count > 0;
+            }
+        }
+    }
 
     public event EventHandler? StatusChanged;
 
@@ -35,12 +50,20 @@ public sealed class WebSocketServerService : IDisposable
         {
             socket.OnOpen = () =>
             {
-                clients.Add(socket);
+                lock (clientsLock)
+                {
+                    clients.Add(socket);
+                }
+
                 StatusChanged?.Invoke(this, EventArgs.Empty);
             };
             socket.OnClose = () =>
             {
-                clients.Remove(socket);
+                lock (clientsLock)
+                {
+                    clients.Remove(socket);
+                }
+
                 StatusChanged?.Invoke(this, EventArgs.Empty);
             };
             socket.OnMessage = HandleRawMessage;
@@ -49,24 +72,37 @@ public sealed class WebSocketServerService : IDisposable
 
     public void Dispose()
     {
-        foreach (var client in clients.ToArray())
+        IWebSocketConnection[] currentClients;
+        lock (clientsLock)
+        {
+            currentClients = clients.ToArray();
+            clients.Clear();
+        }
+
+        foreach (var client in currentClients)
         {
             client.Close();
         }
 
-        clients.Clear();
         server?.Dispose();
     }
 
     private void HandleRawMessage(string rawMessage)
     {
-        var message = JsonSerializer.Deserialize<SyncMessage>(rawMessage);
-        if (message is null)
+        try
+        {
+            var message = JsonSerializer.Deserialize<SyncMessage>(rawMessage, JsonOptions);
+            if (message is null)
+            {
+                return;
+            }
+
+            messageHandler.Handle(message);
+        }
+        catch (JsonException)
         {
             return;
         }
-
-        messageHandler.Handle(message);
     }
 
     private static string ResolveLocalIpAddress()