Cancel C# 4.5 TcpClient ReadAsync by timeout

问题

What would the proper way to cancel TcpClient ReadAsync operation by timeout and catch this timeout event in .NET 4.5?

TcpClient.ReadTimeout seems to be applied to the sync Read only.

UPDATE:
Tried tro apply the approach desribed here Cancelling an Asynchronous Operation

var buffer = new byte[4096];
CancellationTokenSource cts = new CancellationTokenSource(5000);
int amountRead = await tcpClientStream.ReadAsync(buffer, 0, 4096, cts.Token);

but it never cancels by timeout. Is anything wrong?

回答1:

so I know that was from a long time but google still drive me here and I saw there is none marked as answer

for me, I solve like that I make an extension to add a method ReadAsync that takes extra timeout

        public static async Task<int> ReadAsync(this NetworkStream stream, byte[] buffer, int offset, int count, int TimeOut)
    {
        var ReciveCount = 0;
        var receiveTask = Task.Run(async () => { ReciveCount = await stream.ReadAsync(buffer, offset, count); });
        var isReceived = await Task.WhenAny(receiveTask, Task.Delay(TimeOut)) == receiveTask;
        if (!isReceived) return -1;
        return ReciveCount;
    }

so if it returned -1 that mean the read timed out

回答2:

Edit: the following gist is a workaround I did for this. https://gist.github.com/svet93/fb96d8fd12bfc9f9f3a8f0267dfbaf68

Original:

I really liked the answer from Khalid Omar and did my own version of it which I thought was worth sharing:

public static class TcpStreamExtension
{
    public static async Task<int> ReadAsyncWithTimeout(this NetworkStream stream, byte[] buffer, int offset, int count)
    {
        if (stream.CanRead)
        {

            Task<int> readTask = stream.ReadAsync(buffer, offset, count);
            Task delayTask = Task.Delay(stream.ReadTimeout);
            Task task = await Task.WhenAny(readTask, delayTask);

            if (task == readTask)
                    return await readTask;

        }
        return 0;
    }
}

It is more or less the same thing except slightly differently formatted in a way that is more readable (to me), and more importantly it does not use Task.Run I wasn't sure why it was used in his example.

Edit:

The above may seem good in a first glance but I found out it causes some problems. The readAsync call seems to leak if no data comes in, and in my case it seems that it reads a later write and the data is essentially returned within a place in memory no longer used.

回答3:

You have to implement it by yourself: it is not available in that class.

you should use a timer that will kill the async operation after a timespan or use the Read sync version in a a backgroundthread.

there you can find an example: Implementing a timeout with NetworkStream.BeginRead and NetworkStream.EndRead

来源：https://stackoverflow.com/questions/15273784/cancel-c-sharp-4-5-tcpclient-readasync-by-timeout

标签

timeout

tcpclient