Many TcpListener incoming connections

Question

I need to make a server that accepts and keeps for a long time many connections (perspectively over 100k).

My code is below:

public delegate Task ClientConnectedEventHandler(Stream stream);

public class Listener
{
    public event ClientConnectedEventHandler OnClientConnected;

    private readonly TcpListener _tcpListener;

    public Listener()
    {
        _tcpListener = new TcpListener(new IPEndPoint(IPAddress.Any, 8082));
    }

    public void Start()
    {
        _tcpListener.Start();
        _tcpListener.BeginAcceptTcpClient(Accept, null);
    }

    private void Accept(IAsyncResult asyncResult)
    {
        _tcpListener.BeginAcceptTcpClient(Accept, null);
        var client = _tcpListener.EndAcceptTcpClient(asyncResult);
        var stream = client.GetStream();
        OnClientConnected?.Invoke(stream).ContinueWith(_ => client.Close());
    }
}

class Program
{
    static void Main(string[] args)
    {
        var listener = new Listener();
        var count = 0;
        var infoLock = new object();

        listener.OnClientConnected += async stream =>
        {
            lock (infoLock)
            {
                count++;
                Console.Title = count.ToString();
            }
            while (true)
            {
                // Some logic
                await Task.Delay(100);
            }
        };

        listener.Start();
        while (true)
        {
            Thread.Sleep(100);
        }
    }
}

There is no problem when the logic takes up to 300-400 ms. But if I want to keep incoming connections for a long time, count variable increments very slow after accepting 8 clients, moreover appears a trouble with huge memory usage. What I'm doing wrong and how to resolve this?

Answer 1

Your memory issue may be caused by not disposing unmanaged resources. Both TcpClient and NetworkStream implement IDisposable and should be wrapped in Using blocks or manually Closed/Disposed. See How to properly and completely close/reset a TcpClient connection? for starters.