Consider the following simplified example (ready to transfer to LinqPad, an elevated account is required):
void Main()
{
Go();
Thread.Sleep(100000);
}
async void Go()
{
TcpListener listener = new TcpListener(IPAddress.Any, 6666);
try
{
cts.Token.Register(() => Console.WriteLine("Token was canceled"));
listener.Start();
using(TcpClient client = await listener.AcceptTcpClientAsync()
.ConfigureAwait(false))
using(var cts = new CancellationTokenSource(TimeSpan.FromSeconds(5)))
{
var stream=client.GetStream();
var buffer=new byte[64];
try
{
var amtRead = await stream.ReadAsync(buffer,
0,
buffer.Length,
cts.Token);
Console.WriteLine("finished");
}
catch(TaskCanceledException)
{
Console.WriteLine("boom");
}
}
}
finally
{
listener.Stop();
}
}
If I connect the telnet client to localhost:6666and sit idle for 5 seconds, why do I see that the “token was canceled”, but never saw the “boom” (or “finished”)?
Will this NetworkStream not respect cancellation?
I can get around this with a combination of Task.Delay()and Task.WhenAny, but I would rather make it work as expected.
Conversely, the following cancellation example:
async void Go(CancellationToken ct)
{
using(var cts=new CancellationTokenSource(TimeSpan.FromSeconds(5)))
{
try
{
await Task.Delay(TimeSpan.FromSeconds(10),cts.Token)
.ConfigureAwait(false);
}
catch(TaskCanceledException)
{
Console.WriteLine("boom");
}
}
}
Prints a boom, as expected. What's happening?
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