永远不会在HttpWebResponse中结束Stream

Question

我怎样才能读取一些字节并断开连接？我使用这样的代码

using (HttpWebResponse resp = (HttpWebResponse)request.GetResponse())
{
    using (Stream sm = resp.GetResponseStream())
    {
        using (StreamReader sr = new StreamReader(sm, Encoding.Default))
        {
            sr.Read();
            sr.Close();
        }
    }
}

但它等待流的结束

Answer 1

您可能不想使用StreamReader来读取WebResonse流，除非您确定该流包含换行符。 StreamReader喜欢用线条来思考，如果流中没有任何换行符，它就会挂起。

最好的办法是在byte[]缓冲区中读取所需的字节数，然后将其转换为文本。例如：

int BYTES_TO_READ = 1000;
var buffer = new byte[BYTES_TO_READ];

using (HttpWebResponse resp = (HttpWebResponse)request.GetResponse())
{
    using (Stream sm = resp.GetResponseStream())
    {
        int totalBytesRead = 0;
        int bytesRead;
        do
        {
            // You have to do this in a loop because there's no guarantee that
            // all the bytes you need will be ready when you call.
            bytesRead = sm.Read(buffer, totalBytesRead, BYTES_TO_READ-totalBytesRead);
            totalBytesRead += bytesRead;
        } while (totalBytesRead < BYTES_TO_READ);

        // Sometimes WebResponse will hang if you try to close before
        // you've read the entire stream.  So you can abort the request.
        request.Abort();
    }
}

此时，缓冲区具有缓冲区中的第一个BYTES_TO_READ字节。然后，您可以将其转换为字符串，如下所示：

string s = Encoding.Default.GetString(buffer);

或者如果你想使用MemoryStream，你可以在缓冲区上打开StreamReader。

如果你不读所有内容，我有时会遇到WebResponse。我不知道它为什么这样做，我无法可靠地重现它，但我发现如果我在关闭流之前做request.Abort()，一切正常。看到

另一方面，你想要的词是“反应迟钝”，而不是“不负责任”。

Answer 2

你能做这样的事吗？

        string GetWebPageContent(string url)
        {
            string result = string.Empty;
            HttpWebRequest request;
            const int bytesToGet = 1000;
            request = WebRequest.Create(url) as HttpWebRequest;

//get first 1000 bytes
            request.AddRange(0, bytesToGet - 1);

            using (WebResponse response = request.GetResponse())
            {
                using (StreamReader sr = new StreamReader(response.GetResponseStream()))
                {
                    result = sr.ReadToEnd();
                }
            }
            return result;
        }

关键是在您的请求中使用AddRange。

Answer 3

它是因为http 1.1连接是持久连接默认而且tcp连接尚未关闭，所以流量不接收结束。

你可以使用myHttpWebRequest1.KeepAlive = false;所以在http响应之后tcp连接将关闭。

https://msdn.microsoft.com/en-us/library/system.net.httpwebrequest.connection(v=vs.110).aspx#

Answer 4

如果您正在谈论winforms或webforms，我会将请求放入线程池（如果您使用的是.net 4，则为Task）。即使具有良好的处理能力，流也很容易将GUI置于大多数用户不喜欢的等待状态。

Answer 5

我有类似的永不停止的请求解析与此处列出的示例。以下是我提出的消除这些问题的方法：

// url is a string where the request is going.
HttpWebRequest request = WebRequest.Create(url) as HttpWebRequest;

// Do what you have to do with the Request.

StringBuilder builder = new StringBuilder();
int toRead = 1000;

using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
{
    HttpStatusCode status = response.StatusCode;

    using (Stream receiveStream = response.GetResponseStream())
    {
        using (StreamReader readStream = new StreamReader(receiveStream, Encoding.GetEncoding("utf-8")))
        {
            Char[] read = new Char[toRead];
            int count = readStream.Read(read, 0, toRead);

            while (count > 0)
            {
                string str = new String(read, 0, count);
                builder.Append(str);

                count = readStream.Read(read, 0, toRead);
            }

            readStream.Close();
        }   
    }

    response.Close();
}

return builder.ToString();