c# – HttpWebRequest突然停止工作,几个请求后没有收到响应

我正在使用 WPF .net 4.0应用程序.我有一个搜索栏.对于每个搜索令牌,我需要对8个单独的URL执行8个http请求以获取搜索结果.一旦用户停止在搜索栏中输入,我会在400毫秒后向服务器发送8个请求.搜索6到7个搜索令牌的结果非常好.但在那之后突然HttpWebRequest停止了默默工作.没有例外,没有收到任何回复.我正在使用 Windows 7,我也禁用了防火墙.我不知道后续的http请求丢失在哪里.

任何人都可以向我展示灯来解决这个问题吗？

下面是我的HttpWebRequest调用代码.

public static void SendReq(string url)
{
    // Create a new HttpWebRequest object.
    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);

    request.ContentType = "application/x-www-form-urlencoded";
    request.Proxy = new WebProxy("192.168.1.1",8000);

    // Set the Method property to 'POST' to post data to the URI.
    request.Method = "POST";

    // start the asynchronous operation
    request.BeginGetRequestStream(new AsyncCallback(GetRequestStreamCallback),request);

}

private static void GetRequestStreamCallback(IAsyncResult asynchronousResult)
{
    HttpWebRequest request = (HttpWebRequest)asynchronousResult.AsyncState;

    // End the operation
    Stream postStream = request.EndGetRequestStream(asynchronousResult);

    string postData = this.PostData;

    // Convert the string into a byte array. 
    byte[] byteArray = Encoding.UTF8.GetBytes(postData);

    // Write to the request stream.
    postStream.Write(byteArray,byteArray.Length);
    postStream.Close();

    // Start the asynchronous operation to get the response
    request.BeginGetResponse(new AsyncCallback(GetResponseCallback),request);
}

private static void GetResponseCallback(IAsyncResult asynchronousResult)
{
    HttpWebRequest request = (HttpWebRequest)asynchronousResult.AsyncState;

    // End the operation
    using(HttpWebResponse response = (HttpWebResponse)request.EndGetResponse(asynchronousResult))
    {
        using(Stream streamResponse = response.GetResponseStream())
        {
             using(StreamReader streamRead = new StreamReader(streamResponse))
             {
                 string responseString = streamRead.ReadToEnd();
                 Debug.WriteLine(responseString);
             }
        }
    }
}

ServicePointManager.DefaultConnectionLimit = 20;