Update .gitignore to exclude TypeScript build info and add dist directory. Expand README with project overview, technology stack, prerequisites, and instructions for running and testing the application.

src/HSchool.Server/Net/ClientRegistry.cs

@@ -0,0 +1,42 @@
+using System.Collections.Concurrent;
+using System.Net.WebSockets;
+
+namespace HSchool.Server.Net;
+
+/// <summary>Tracks live connections and hands out player ids.</summary>
+internal sealed class ClientRegistry
+{
+    private readonly ConcurrentDictionary<uint, GameClient> _clients = new();
+    private uint _nextPlayerId;
+
+    public int Count => _clients.Count;
+
+    public GameClient Add(WebSocket socket)
+    {
+        var playerId = Interlocked.Increment(ref _nextPlayerId);
+        var client = new GameClient(playerId, socket);
+        _clients[playerId] = client;
+        return client;
+    }
+
+    public void Remove(uint playerId) => _clients.TryRemove(playerId, out _);
+
+    /// <summary>
+    /// Queues the same frame for every client that finished its handshake; the buffer must not
+    /// be reused afterwards.
+    /// </summary>
+    public int Broadcast(ReadOnlyMemory<byte> frame)
+    {
+        var recipients = 0;
+
+        foreach (var client in _clients.Values)
+        {
+            if (client.IsReady && client.TrySend(frame))
+            {
+                recipients++;
+            }
+        }
+
+        return recipients;
+    }
+}