c# - AcceptTcpClient 和 AcceptTcpClientAsync 区别

Question

据我了解，这些行:

var client = await listener.AcceptTcpClientAsync();

var client = listener.AcceptTcpClient();

应该以同样的方式工作，但是如果我尝试打开，例如，5k 连接(而不关闭它们)，监听器(异步)很快就会停止响应或抛出异常。

有人知道哪里出了问题吗？

示例类:

class ListenerTest
{
    static int connectionNumber = 0;
    static int port = 23456;

    public void StartListening(bool async)
    {
        var listener = new TcpListener(IPAddress.Any, port);
        listener.Start();

        if (async)
        {
            var task = HandleConnectionsAsync(listener);
            task.Wait();
        }
        else
            HandleConnections(listener);
    }

    async Task HandleConnectionsAsync(TcpListener listener)
    {
        while (true)
        {
            Console.Write("Waiting for async connection...");
            var client = await listener.AcceptTcpClientAsync();
            Console.WriteLine("OK #" + connectionNumber);
            connectionNumber++;
        }
    }

    void HandleConnections(TcpListener listener)
    {
        while (true)
        {
            Console.Write("Waiting for sync connection...");
            var client = listener.AcceptTcpClient();
            Console.WriteLine("OK #" + connectionNumber);
            connectionNumber++;
        }
    }

    public static void ConnectTest(int count)
    {
        var ep = new IPEndPoint(IPAddress.Loopback, port);
        for (var i = 0; i < count; i++)
            new TcpClient().Connect(ep);
    }
}

用法:

static void Main(string[] args)
{
    var isAsync = true;
    ThreadPool.QueueUserWorkItem(new WaitCallback(StartListening), isAsync);
    ListenerTest.ConnectTest(5000);
}

static void StartListening(object state)
{
    var my = new ListenerTest();
    my.StartListening((bool)state);
}

Answer 1

您的测试连接被 GC 杀死，如果您“固定”您的连接直到测试结束 - 您将获得 5000 个连接(我刚刚复制/粘贴并修复/测试了您的代码)。重写的连接测试:

    public static void ConnectTest(int count)
    {
        var ep = new IPEndPoint(IPAddress.Loopback, port);
        List<TcpClient> clients = new List<TcpClient>();
        for (var i = 0; i < count; i++)
        {
            TcpClient cl = new TcpClient();
            clients.Add(cl);
            cl.Connect(ep);
        }
    }

另请注意，在“真实世界”条件下，您需要在开始监听器循环之前添加如下内容:

ThreadPool.SetMinThreads(100, 100);

这让您的代码在“突发”连接计数/网络负载下工作。我们刚刚在 linux/mono 下成功地“负载测试”了 7,5K 个连接。