await UDPClient.ReceiveAsync with timeout

问题

I'm using UDPClient like below

dim c = New UDPClient(port)
client.CLient.ReceiveTimeout = 1
await client.ReceiveAsync()

However the await does not terminate or throw even though I have set a timeout. Is this normal behaviour?

回答1:

It is explicitly mentioned in the MSDN Library article for Socket.ReceiveTimeout:

Gets or sets a value that specifies the amount of time after which a synchronous Receive call will time out.

Emphasis added. You are doing the opposite of a synchronous receive when you use ReceiveAsync(). The workaround is to use a System.Timers.Timer that you start before the call and stop afterwards. Close the socket in the Elapsed event handler so the ReceiveAsync() method terminates with an ObjectDisposed exception.

回答2:

Yes. The asynchronous methods on Socket do not implement the timeouts. If you need timeouts on asynchronous operations, you have to create them yourself (e.g., using Task.Delay and Task.WhenAny).

回答3:

I had this issue recently and this is how I solved it:

async Task Listen(IPEndPoint ep, int timeout)
{
    using (var udp = new UdpClient(ep))
    {
        var result = await Task.Run(() =>
        {
            var task = udp.ReceiveAsync();
            task.Wait(timeout);
            if (task.IsCompleted)
            { return task.Result; }
            throw new TimeoutException();
        });

        Receive(result); // use the result
    }
}

来源：https://stackoverflow.com/questions/12638104/await-udpclient-receiveasync-with-timeout