NetworkStream.ReadAsync with a cancellation token never cancels

Question

Here the proof.
Any idea what is wrong in this code ?

    [TestMethod]
    public void TestTest()
    {
        var tcp = new TcpClient() { ReceiveTimeou         


        

Answer 1

There are a few problems there that pop out:

1. CancellationToken throws OperationCanceledException, not TimeoutException (cancellation is not always due to timeout).
2. ReceiveTimeout doesn't apply, since you're doing an asynchronous read. Even if it did, you'd have a race condition between IOException and OperationCanceledException.
3. Since you're synchronously connecting the socket, you'll want a high timeout on this test (IIRC, the default connection timeout is ~90 seconds, but can be changed as Windows monitors the network speeds).

4. The correct way to test asynchronous code is with an asynchronous test:

   [TestMethod]
   public async Task TestTest()
   {
       var tcp = new TcpClient() { ReceiveTimeout = 5000, SendTimeout = 20000 };
       tcp.Connect(IPAddress.Parse("176.31.100.115"), 25);
       await Read(tcp.GetStream());
   }