c# - 对 TcpClient.ConnectAsync 方法的取消支持

Question

我希望得到一些关于为我正在处理的工作增加弹性的意见，该工作涉及异步创建多个 TcpClient 连接到各种服务器，一旦成功建立 TCP 连接，然后存储TcpClient 是一个集合(只是需求的摘录)

这是我目前所拥有的:

internal class Program
{
    private static readonly TcpClient _client = new TcpClient(AddressFamily.InterNetwork);
    private static SslStream _stream;

    private static async Task Main(string[] args)
    {
        var timeoutTask = Task.Delay(5000);
        var connectTask = _client.ConnectAsync("10.14.16.24", 56564);

        var completedTask = await Task.WhenAny(timeoutTask, connectTask);
        if (completedTask == timeoutTask)
            _client.Dispose();

        try
        {
            await connectTask;
            _stream = new SslStream(_client.GetStream(), false);
        }
        catch (SocketException e)
        {
            Console.WriteLine(e.Message);
        }
    }
}

问题:如果发生超时，connectTask 状态仍然是“WaitingForActivation”，直到 ConnectAsync 方法返回 Faulted 或RanToCompletion。如何取消此任务，知道 ConnectAsync 不支持 CancellationToken

欢迎提出任何建议或改进。谢谢

Answer 1

您的里程数可能因您使用的 .net 而异

using System;
using System.Net.Sockets;
using System.Threading;
using System.Threading.Tasks;

namespace TcpClientCancellation
{
    public static class Extensions
    {
        public static async Task ConnectAsync(this TcpClient tcpClient, string host, int port, CancellationToken cancellationToken) {
            if (tcpClient == null) {
                throw new ArgumentNullException(nameof(tcpClient));
            }

            cancellationToken.ThrowIfCancellationRequested();

            using (cancellationToken.Register(() => tcpClient.Close())) {
                try {
                    cancellationToken.ThrowIfCancellationRequested();

                    await tcpClient.ConnectAsync(host, port).ConfigureAwait(false);
                } catch (NullReferenceException) when (cancellationToken.IsCancellationRequested) {
                    cancellationToken.ThrowIfCancellationRequested();
                }
            }
        }
    }
}