C# 使用HttpWebRequest和StreamReader下载网页时发生未处理的异常

这是一个使用.NET4.0的C#应用程序

背景：

Unable to read data from the transport connection:
An existing connection was forcibly closed by the remote host.
at System.Net.ConnectStream.Read(Byte[] buffer, Int32 offset, Int32 size)
at System.IO.StreamReader.ReadBuffer() at System.IO.StreamReader.ReadToEnd()
at ProjectName.ClassNetwork.DownloadFile(String _IP, Int32 _Port, String _File)
at ProjectName.FormMain.GetIFile(ClassSensor Sensor, String& RawHolder, String[] FileData)
at ProjectName.FormMain.GetLegacyData(ClassSensor Sensor)
at ProjectName.FormMain.threader_Download(Object SensorObject)
at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart(Object obj)

private static object[] DownloadFile(string _IP, int _Port, string _File)
{
    string uri = String.Format("http://{0}:{1}/{2}", _IP, _Port, _File);
    string Status = String.Empty;
    string Data = String.Empty;
    HttpWebResponse Response = null;

    try
    {
        HttpWebRequest webReq = (HttpWebRequest) WebRequest.Create(uri);
        webReq.Timeout = 10000;
        webReq.ReadWriteTimeout = 30000;
        Response = (HttpWebResponse) webReq.GetResponse();
        using (Stream dataStream = Response.GetResponseStream())
            if (dataStream != null)
                using (StreamReader reader = new StreamReader(dataStream))
                    try
                    {
                        // This line causes crashes if remote computer closes connection
                        Data = reader.ReadToEnd();
                    }
                    catch { } // Inner try/catch added to no avail
        Response.Close();
    }
    catch (WebException exc)
    {
        // Connection Error
        Status = exc.Status.ToString();
        Data = String.Empty;
    }
    catch (Exception exc)
    {
        // Other error
        Status = exc.Message;
        Data = String.Empty;
    }

    if (Response != null && Response.StatusCode != HttpStatusCode.OK)
    {
        Status = Response.StatusCode.ToString();
        Data = String.Empty;
    }

    return new object[] { Status, Data };
}

我一直在尝试改进一个应用程序的一部分，它可以从多个web服务器下载文件。除了偶尔远程计算机关闭连接的情况外，一切正常。我认为这可能是由于多种因素造成的，包括网络问题、电源问题等。如果连接关闭，我只想跳过下载。但是，目前应用程序导致异常，该异常由

AppDomain.CurrentDomain.UnhandledException

的处理程序拾取。堆栈跟踪如下所示：

堆栈跟踪：

Unable to read data from the transport connection:
An existing connection was forcibly closed by the remote host.
at System.Net.ConnectStream.Read(Byte[] buffer, Int32 offset, Int32 size)
at System.IO.StreamReader.ReadBuffer() at System.IO.StreamReader.ReadToEnd()
at ProjectName.ClassNetwork.DownloadFile(String _IP, Int32 _Port, String _File)
at ProjectName.FormMain.GetIFile(ClassSensor Sensor, String& RawHolder, String[] FileData)
at ProjectName.FormMain.GetLegacyData(ClassSensor Sensor)
at ProjectName.FormMain.threader_Download(Object SensorObject)
at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart(Object obj)

private static object[] DownloadFile(string _IP, int _Port, string _File)
{
    string uri = String.Format("http://{0}:{1}/{2}", _IP, _Port, _File);
    string Status = String.Empty;
    string Data = String.Empty;
    HttpWebResponse Response = null;

    try
    {
        HttpWebRequest webReq = (HttpWebRequest) WebRequest.Create(uri);
        webReq.Timeout = 10000;
        webReq.ReadWriteTimeout = 30000;
        Response = (HttpWebResponse) webReq.GetResponse();
        using (Stream dataStream = Response.GetResponseStream())
            if (dataStream != null)
                using (StreamReader reader = new StreamReader(dataStream))
                    try
                    {
                        // This line causes crashes if remote computer closes connection
                        Data = reader.ReadToEnd();
                    }
                    catch { } // Inner try/catch added to no avail
        Response.Close();
    }
    catch (WebException exc)
    {
        // Connection Error
        Status = exc.Status.ToString();
        Data = String.Empty;
    }
    catch (Exception exc)
    {
        // Other error
        Status = exc.Message;
        Data = String.Empty;
    }

    if (Response != null && Response.StatusCode != HttpStatusCode.OK)
    {
        Status = Response.StatusCode.ToString();
        Data = String.Empty;
    }

    return new object[] { Status, Data };
}

我最初有WebException和Exception的try/catch，但他们没有捕捉到这个特定的错误。我添加了最里面的try/catch，试图避免这个问题，但没有效果。我应该提到，这个方法是由UI线程以外的线程调用的，这可能是try/catch块看起来不起作用的部分原因。请原谅我在多线程错误捕获方面是个新手

问题：

Unable to read data from the transport connection:
An existing connection was forcibly closed by the remote host.
at System.Net.ConnectStream.Read(Byte[] buffer, Int32 offset, Int32 size)
at System.IO.StreamReader.ReadBuffer() at System.IO.StreamReader.ReadToEnd()
at ProjectName.ClassNetwork.DownloadFile(String _IP, Int32 _Port, String _File)
at ProjectName.FormMain.GetIFile(ClassSensor Sensor, String& RawHolder, String[] FileData)
at ProjectName.FormMain.GetLegacyData(ClassSensor Sensor)
at ProjectName.FormMain.threader_Download(Object SensorObject)
at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart(Object obj)

private static object[] DownloadFile(string _IP, int _Port, string _File)
{
    string uri = String.Format("http://{0}:{1}/{2}", _IP, _Port, _File);
    string Status = String.Empty;
    string Data = String.Empty;
    HttpWebResponse Response = null;

    try
    {
        HttpWebRequest webReq = (HttpWebRequest) WebRequest.Create(uri);
        webReq.Timeout = 10000;
        webReq.ReadWriteTimeout = 30000;
        Response = (HttpWebResponse) webReq.GetResponse();
        using (Stream dataStream = Response.GetResponseStream())
            if (dataStream != null)
                using (StreamReader reader = new StreamReader(dataStream))
                    try
                    {
                        // This line causes crashes if remote computer closes connection
                        Data = reader.ReadToEnd();
                    }
                    catch { } // Inner try/catch added to no avail
        Response.Close();
    }
    catch (WebException exc)
    {
        // Connection Error
        Status = exc.Status.ToString();
        Data = String.Empty;
    }
    catch (Exception exc)
    {
        // Other error
        Status = exc.Message;
        Data = String.Empty;
    }

    if (Response != null && Response.StatusCode != HttpStatusCode.OK)
    {
        Status = Response.StatusCode.ToString();
        Data = String.Empty;
    }

    return new object[] { Status, Data };
}

• 如何改进此方法并正确处理连接中途失败的情况

---

代码：

Unable to read data from the transport connection:
An existing connection was forcibly closed by the remote host.
at System.Net.ConnectStream.Read(Byte[] buffer, Int32 offset, Int32 size)
at System.IO.StreamReader.ReadBuffer() at System.IO.StreamReader.ReadToEnd()
at ProjectName.ClassNetwork.DownloadFile(String _IP, Int32 _Port, String _File)
at ProjectName.FormMain.GetIFile(ClassSensor Sensor, String& RawHolder, String[] FileData)
at ProjectName.FormMain.GetLegacyData(ClassSensor Sensor)
at ProjectName.FormMain.threader_Download(Object SensorObject)
at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart(Object obj)

private static object[] DownloadFile(string _IP, int _Port, string _File)
{
    string uri = String.Format("http://{0}:{1}/{2}", _IP, _Port, _File);
    string Status = String.Empty;
    string Data = String.Empty;
    HttpWebResponse Response = null;

    try
    {
        HttpWebRequest webReq = (HttpWebRequest) WebRequest.Create(uri);
        webReq.Timeout = 10000;
        webReq.ReadWriteTimeout = 30000;
        Response = (HttpWebResponse) webReq.GetResponse();
        using (Stream dataStream = Response.GetResponseStream())
            if (dataStream != null)
                using (StreamReader reader = new StreamReader(dataStream))
                    try
                    {
                        // This line causes crashes if remote computer closes connection
                        Data = reader.ReadToEnd();
                    }
                    catch { } // Inner try/catch added to no avail
        Response.Close();
    }
    catch (WebException exc)
    {
        // Connection Error
        Status = exc.Status.ToString();
        Data = String.Empty;
    }
    catch (Exception exc)
    {
        // Other error
        Status = exc.Message;
        Data = String.Empty;
    }

    if (Response != null && Response.StatusCode != HttpStatusCode.OK)
    {
        Status = Response.StatusCode.ToString();
        Data = String.Empty;
    }

    return new object[] { Status, Data };
}

跟踪日志：

Unable to read data from the transport connection:
An existing connection was forcibly closed by the remote host.
at System.Net.ConnectStream.Read(Byte[] buffer, Int32 offset, Int32 size)
at System.IO.StreamReader.ReadBuffer() at System.IO.StreamReader.ReadToEnd()
at ProjectName.ClassNetwork.DownloadFile(String _IP, Int32 _Port, String _File)
at ProjectName.FormMain.GetIFile(ClassSensor Sensor, String& RawHolder, String[] FileData)
at ProjectName.FormMain.GetLegacyData(ClassSensor Sensor)
at ProjectName.FormMain.threader_Download(Object SensorObject)
at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart(Object obj)

private static object[] DownloadFile(string _IP, int _Port, string _File)
{
    string uri = String.Format("http://{0}:{1}/{2}", _IP, _Port, _File);
    string Status = String.Empty;
    string Data = String.Empty;
    HttpWebResponse Response = null;

    try
    {
        HttpWebRequest webReq = (HttpWebRequest) WebRequest.Create(uri);
        webReq.Timeout = 10000;
        webReq.ReadWriteTimeout = 30000;
        Response = (HttpWebResponse) webReq.GetResponse();
        using (Stream dataStream = Response.GetResponseStream())
            if (dataStream != null)
                using (StreamReader reader = new StreamReader(dataStream))
                    try
                    {
                        // This line causes crashes if remote computer closes connection
                        Data = reader.ReadToEnd();
                    }
                    catch { } // Inner try/catch added to no avail
        Response.Close();
    }
    catch (WebException exc)
    {
        // Connection Error
        Status = exc.Status.ToString();
        Data = String.Empty;
    }
    catch (Exception exc)
    {
        // Other error
        Status = exc.Message;
        Data = String.Empty;
    }

    if (Response != null && Response.StatusCode != HttpStatusCode.OK)
    {
        Status = Response.StatusCode.ToString();
        Data = String.Empty;
    }

    return new object[] { Status, Data };
}

根据Feroze的建议，我运行了一个跟踪点，结果如下：

System.Net Error: 0 : [2164] Exception in the
#46104728::UnhandledExceptionHandler - Stream was not readable.
System.Net Error: 0 : [2164]     at System.IO.BinaryReader..ctor(Stream input, Encoding encoding)
at ProjectName.ClassNetwork.DLStream(ClassSensor Sensor)
at ProjectName.ClassNetwork.DownloadFile(ClassSensor Sensor)
at ProjectName.FormMain.GetStreamFile(ClassSensor Sensor)
at ProjectName.FormMain.threader_Download(Object SensorObject)
at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncctx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart(Object obj)

---

从堆栈中，我看不出这是线程池线程抛出的异常，您无法捕获它。显然，从堆栈上看，它似乎是由应用程序线程上调用的ConnectStream:：Read方法引发的。

从堆栈上看，我看不出这是线程池线程引发的异常，您无法捕获。显然，从堆栈中看，它似乎是由应用程序线程上调用的ConnectStream:：Read方法抛出的。

我找不到任何问号，表明您也需要回答一个问题。代码前的最后一句话。如果您希望将其表述为一个问题：“如何改进此方法并正确处理中途连接失败的情况？”您能否发布完整（未修剪）堆栈跟踪？我将编辑此问题以包含所有内容。我找不到任何问号，表明您也需要回答某个问题。最后一句，在代码之前。如果您希望将其表述为一个问题：“如何改进此方法并正确处理中途连接失败的情况？”您能否发布完整（未修剪）堆栈跟踪？我将编辑此问题以包括所有内容。我希望创建tracelog以尝试解决此问题。你能提供更多关于编辑哪个配置文件的信息吗？您的博客假设我对tracelog设施的了解比我多一点。：）Feroze，我已经成功地将tracelog功能添加到app.config中。（一开始我不确定这需要什么文件。）错误是不可预测的，但应该在24小时内发生。这将是一个巨大的文件，因此一旦出现错误，我将尝试将其修剪到相关部分。感谢到目前为止的帮助。我正在将tracelog的结果添加到我的问题中。我想创建tracelog以尝试解决此问题。你能提供更多关于编辑哪个配置文件的信息吗？您的博客假设我对tracelog设施的了解比我多一点。：）Feroze，我已经成功地将tracelog功能添加到app.config中。（一开始我不确定这需要什么文件。）错误是不可预测的，但应该在24小时内发生。这将是一个巨大的文件，因此一旦出现错误，我将尝试将其修剪到相关部分。谢谢你到目前为止的帮助。我正在把tracelog的结果添加到我的问题中。