[英]Catch unhandled SocketException during asynchronous HttpWebResponse read
對HttpWebRequest.BeginGetResponse / EndGetResponse和HttpWebResponse.GetResponseStream()。BeginRead / EndRead的所有異步調用都是從try / catch塊進行的,但是,這些異常會傳播並且不會留下處理它們並停止應用程序終止的機會:
未處理的異常:System.IO.IOException:無法從傳輸連接中讀取數據: 建立的連接已被主機中的軟件中止。 ---> System.Net.Sockets.SocketException:建立的連接被主機中的軟件中止了
未處理的異常:System.IO.IOException:無法從傳輸連接讀取數據: 現有連接被遠程主機強行關閉。 ---> System.Net.Sockets.SocketException:現有的連接被遠程主機強行關閉
Unhandled Exception: System.IO.IOException: Unable to read data from the transport connection: An established connection was aborted by the software in your host machine. ---> System.Net.Sockets.SocketException: An established connection was aborted by the software in your host machine
at System.Net.Sockets.Socket.BeginReceive(Byte[] buffer, Int32 offset, Int32 size, SocketFlags socketFlags, AsyncCallback callback, Object state)
at System.Net.Sockets.NetworkStream.BeginRead(Byte[] buffer, Int32 offset, Int32 size, AsyncCallback callback, Object state)
--- End of inner exception stack trace ---
at System.Net.Sockets.NetworkStream.BeginRead(Byte[] buffer, Int32 offset, Int32 size, AsyncCallback callback, Object state)
at System.Net.PooledStream.BeginRead(Byte[] buffer, Int32 offset, Int32 size, AsyncCallback callback, Object state)
at System.Net.ConnectStream.BeginReadWithoutValidation(Byte[] buffer, Int32 offset, Int32 size, AsyncCallback callback, Object state)
at System.Net.ConnectStream.BeginRead(Byte[] buffer, Int32 offset, Int32 size, AsyncCallback callback, Object state)
at System.IO.Compression.DeflateStream.ReadCallback(IAsyncResult baseStreamResult)
at System.Net.LazyAsyncResult.Complete(IntPtr userToken)
at System.Net.ContextAwareResult.CompleteCallback(Object state)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Net.ContextAwareResult.Complete(IntPtr userToken)
at System.Net.LazyAsyncResult.ProtectedInvokeCallback(Object result, IntPtr userToken)
at System.Net.Sockets.BaseOverlappedAsyncResult.CompletionPortCallback(UInt32 errorCode, UInt32 numBytes, NativeOverlapped* nativeOverlapped)
at System.Threading._IOCompletionCallback.PerformIOCompletionCallback(UInt32 errorCode, UInt32 numBytes, NativeOverlapped* pOVERLAP)
實際代碼片段:
public static RequestState StartDownload(string url, string referer, RequestData data, DownloadEventHandler completedHandler, DownloadExceptionHandler failedHandler)
{
RequestState state = null;
try
{
var request = CreateWebRequest(url, referer, data);
state = new RequestState(url, data, request)
{
DownloadCompleted = completedHandler;
DownloadFailed = failedHandler;
}
state.ResponseAsyncResult = request.BeginGetResponse(WebResponseCallback, state);
state.AsyncTimeoutHandle = ThreadPool.RegisterWaitForSingleObject(state.CompletedHandle, DownloadTimeoutCallback, state, TimeSpan.FromSeconds(data.DownloadTimeout), true);
}
catch(Exception ex)
{
Trace.TraceError(ex.ToString());
}
return state;
}
private static void DownloadTimeoutCallback(object state, bool timedOut)
{
var requestState = (RequestState)state;
try
{
requestState.AsyncTimeoutHandle.Unregister(null);
if(timedOut)
{
requestState.Request.Abort();
}
}
catch(Exception ex)
{
Trace.TraceError(ex.ToString());
}
}
private static void WebResponseCallback(IAsyncResult asyncResult)
{
var state = (RequestState)asyncResult.AsyncState;
try
{
var response = (HttpWebResponse)state.Request.EndGetResponse(asyncResult);
WebResponse(state, response);
}
catch (Exception ex)
{
Trace.TraceError(ex.ToString());
}
}
private static void WebResponse(RequestState state, HttpWebResponse response)
{
state.ActualUrl = state.Request.Address.ToString();
state.Response = response;
BeginRead(state);
}
private static void BeginRead(RequestState state)
{
var stream = state.Response.GetResponseStream();
state.ReadAsyncResult = stream.BeginRead(state.Buffer, 0, state.BufferSize, ReadCallBack, state);
}
private static void ReadCallBack(IAsyncResult asyncResult)
{
var state = (RequestState)asyncResult.AsyncState;
try
{
var stream = state.Response.GetResponseStream();
var bytesRead = stream.EndRead(asyncResult);
if (bytesRead > 0)
{
//there is still more data to read
state.AppendResponseData(state.Buffer, 0, bytesRead);
BeginRead(state);
}
else
{
state.Response.Close();
state.InvokeDownloadCompleted();
}
}
catch(Exception ex)
{
Trace.TraceError(ex.ToString());
}
}
PS:在Microsoft Connect https://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=510564上提交了一個錯誤報告。
我認為原因是異常是在與啟動BegainGetResponse的線程不同的線程上引發的,這解釋了調用堆棧中的System.Threading.ExecutionContext.Run
調用。 這種情況可能是您在引發異常之前退出了try catch塊,因此它沒有任何處理程序就可以引發,請您發布代碼的一部分,以便我了解如何改進它
由Microsoft發布於2009年11月16日上午11:14
.NET 4.0框架中已解決此問題。
謝謝,
網絡類庫團隊
https://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=510564
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