public class TcpGateway
{
    private TcpListener _listener;
    private ConcurrentDictionary<string, Socket> _clients = new();

    public async Task StartAsync(string ip, int port)
    {
        _listener = new TcpListener(IPAddress.Parse(ip), port);
        await _listener.StartAsync();
        
        while (true)
        {
            var client = await _listener.AcceptTcpClientAsync();
            _ = HandleClientAsync(client);
        }
    }

    private async Task HandleClientAsync(TcpClient client)
    {
        using (client)
        {
            var stream = client.GetStream();
            var buffer = new byte[1024 * 4];
            
            while (client.Connected)
            {
                int bytesRead = await stream.ReadAsync(buffer, 0, buffer.Length);
                if (bytesRead == 0) break;

                var msg = MessageParser.Decode(buffer, bytesRead);
                await MessageDispatcher.Dispatch(msg);
            }
        }
    }
}

public class MessageProtocol
{
    public ushort Magic { get; set; } = 0xA55A;
    public byte Version { get; set; }
    public MessageType Type { get; set; }
    public int BodyLength { get; set; }
    public byte[] Body { get; set; }
}

public enum MessageType
{
    Login = 1,
    Text = 2,
    File = 3,
    Heartbeat = 4
}

public static class MessageDispatcher
{
    public static async Task Dispatch(MessageProtocol msg)
    {
        switch (msg.Type)
        {
            case MessageType.Login:
                await AuthService.Authenticate(msg.Body);
                break;
            case MessageType.Text:
                await ChatService.SendMessage(msg);
                break;
            case MessageType.File:
                await FileService.Upload(msg);
                break;
            case MessageType.Heartbeat:
                HeartbeatManager.KeepAlive(msg.SessionId);
                break;
        }
    }
}

// 使用線程池優(yōu)化資源
ThreadPool.SetMinThreads(50, 50);

// 異步處理消息
public async Task ProcessMessageAsync(Socket socket)
{
    var buffer = new byte[1024 * 10];
    while (true)
    {
        int bytesRead = await socket.ReceiveAsync(
            new ArraySegment<byte>(buffer), 
            SocketFlags.None);
        
        if (bytesRead == 0) break;
        
        _ = Task.Run(() => HandleData(buffer, bytesRead));
    }
}

public class ChatRepository
{
    private readonly DbContext _context;

    public async Task SaveMessage(ChatMessage message)
    {
        _context.Messages.Add(message);
        await _context.SaveChangesAsync();
        
        // 寫(xiě)入Redis消息隊(duì)列
        await Redis.PublishAsync("chat_messages", message);
    }
}

public class FileTransferService
{
    public async Task SendFile(string filePath, Socket client)
    {
        using (var fileStream = File.OpenRead(filePath))
        {
            var buffer = new byte[1024 * 1024]; // 1MB分塊
            int bytesRead;
            
            while ((bytesRead = await fileStream.ReadAsync(buffer, 0, buffer.Length)) > 0)
            {
                await client.SendAsync(
                    new ArraySegment<byte>(buffer, 0, bytesRead),
                    SocketFlags.None);
            }
        }
    }
}

public class SecurityManager
{
    private readonly SslStream _sslStream;

    public async Task EstablishSecureConnectionAsync(Socket socket)
    {
        _sslStream = new SslStream(socket.GetStream(), false);
        await _sslStream.AuthenticateAsServerAsync(serverCertificate);
    }

    public byte[] EncryptData(byte[] data)
    {
        return _sslStream.Encrypt(data);
    }
}

public class HeartbeatMonitor
{
    private readonly ConcurrentDictionary<string, DateTime> _sessions = new();

    public void UpdateHeartbeat(string sessionId)
    {
        _sessions[sessionId] = DateTime.Now;
    }

    public bool CheckTimeout(string sessionId, int timeoutSeconds = 30)
    {
        return (DateTime.Now - _sessions[sessionId]).TotalSeconds > timeoutSeconds;
    }
}

public class GroupService
{
    public async Task CreateGroup(string groupName, List<string> members)
    {
        var groupId = Guid.NewGuid().ToString();
        await _redis.HashSetAsync($"group:{groupId}", 
            new HashEntry[] { 
                new("name", groupName),
                new("members", string.Join(",", members))
            });
    }
}

public class MessageService
{
    public async Task RecallMessage(string msgId)
    {
        var msg = await _redis.GetAsync<Message>($"msg:{msgId}");
        if (msg != null && msg.Timestamp > DateTime.Now.AddMinutes(-2))
        {
            await _redis.PublishAsync("recall_message", msgId);
        }
    }
}