Softlionの回答の説明によると：
Task.WaitAny を使用して、非同期呼び出しを遅延タスク (Task.Delay) と組み合わせます。io タスクの前に遅延が経過したら、ストリームを閉じます。これにより、タスクが強制的に停止されます。io タスクで非同期例外を正しく処理する必要があります。そして、dealy タスクと io タスクの両方に継続タスクを追加する必要があります。
タイムアウト付きの非同期読み取りを提供するコードをいくつか作成しました。
using System;
using System.Net.Sockets;
using System.Threading.Tasks;
namespace ConsoleApplication2013
{
class Program
{
/// <summary>
/// Does an async read on the supplied NetworkStream and will timeout after the specified milliseconds.
/// </summary>
/// <param name="ns">NetworkStream object on which to do the ReadAsync</param>
/// <param name="s">Socket associated with ns (needed to close to abort the ReadAsync task if the timeout occurs)</param>
/// <param name="timeoutMillis">number of milliseconds to wait for the read to complete before timing out</param>
/// <param name="buffer"> The buffer to write the data into</param>
/// <param name="offset">The byte offset in buffer at which to begin writing data from the stream</param>
/// <param name="amountToRead">The maximum number of bytes to read</param>
/// <returns>
/// a Tuple where Item1 is true if the ReadAsync completed, and false if the timeout occurred,
/// and Item2 is set to the amount of data that was read when Item1 is true
/// </returns>
public static async Task<Tuple<bool, int>> ReadWithTimeoutAsync(NetworkStream ns, Socket s, int timeoutMillis, byte[] buffer, int offset, int amountToRead)
{
Task<int> readTask = ns.ReadAsync(buffer, offset, amountToRead);
Task timeoutTask = Task.Delay(timeoutMillis);
int amountRead = 0;
bool result = await Task.Factory.ContinueWhenAny<bool>(new Task[] { readTask, timeoutTask }, (completedTask) =>
{
if (completedTask == timeoutTask) //the timeout task was the first to complete
{
//close the socket (unless you set ownsSocket parameter to true in the NetworkStream constructor, closing the network stream alone was not enough to cause the readTask to get an exception)
s.Close();
return false; //indicate that a timeout occurred
}
else //the readTask completed
{
amountRead = readTask.Result;
return true;
}
});
return new Tuple<bool, int>(result, amountRead);
}
#region sample usage
static void Main(string[] args)
{
Program p = new Program();
Task.WaitAll(p.RunAsync());
}
public async Task RunAsync()
{
Socket s = new Socket(SocketType.Stream, ProtocolType.Tcp);
Console.WriteLine("Connecting...");
s.Connect("127.0.0.1", 7894); //for a simple server to test the timeout, run "ncat -l 127.0.0.1 7894"
Console.WriteLine("Connected!");
NetworkStream ns = new NetworkStream(s);
byte[] buffer = new byte[1024];
Task<Tuple<bool, int>> readWithTimeoutTask = Program.ReadWithTimeoutAsync(ns, s, 3000, buffer, 0, 1024);
Console.WriteLine("Read task created");
Tuple<bool, int> result = await readWithTimeoutTask;
Console.WriteLine("readWithTimeoutTask is complete!");
Console.WriteLine("Read succeeded without timeout? " + result.Item1 + "; Amount read=" + result.Item2);
}
#endregion
}
}