using System.Net;
using System.Net.Sockets;

while (true)
{
    using var serverSocket =  new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
    serverSocket.Bind(new IPEndPoint(IPAddress.Loopback, 0));
    serverSocket.Listen();

    using var socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
    using var cts = new CancellationTokenSource();

    ValueTask connectTask = socket.ConnectAsync(serverSocket.LocalEndPoint!, cts.Token);
    using var _ = await serverSocket.AcceptAsync();
    cts.Cancel();

    try
    {
        await connectTask;
        if (!socket.Connected)
        {
            Console.Error.WriteLine("unexpected non-connected socket after successfull ConnectAsync");
            return 1;
        }
    }
    catch (OperationCanceledException)
    {
        // Expected if canceled before connect.
    }
}