Does anyone know why I receive an HttpWebRequest T

问题:

I was wondering if you can help me with a bug I ma having. I have a HTTP Manager I have created that helps me dealing with POSTing/GETing data from websites. It has worked fine until recently when I am trying to use a mixture of both. First loop round everything works, on the second loop it hangs on HttpWebRequest.GetRequestStream(). I have read all over the net and have found no real solution. Below are the codeblocks for the fetching/receiving:

 ASCIIEncoding encoding = new ASCIIEncoding();
 byte[] buffer = encoding.GetBytes(_PostData);

_HttpWebRequest = (HttpWebRequest)WebRequest.Create(_FetchUrl);
_HttpWebRequest.Credentials = _Credentials;
_HttpWebRequest.Method = _RequestType.ToString();
_HttpWebRequest.ContentType = "application/x-www-form-urlencoded";
_HttpWebRequest.ContentLength = buffer.Length;
_HttpWebRequest.UserAgent = userAgent;
_HttpWebRequest.CookieContainer = _CookieContainer;
_HttpWebRequest.KeepAlive = false;
_HttpWebRequest.AllowAutoRedirect = _AllowAutoRedirect;
_HttpWebRequest.AutomaticDecompression = DecompressionMethods.GZip;
_HttpWebRequest.ServicePoint.Expect100Continue = false;  

 if (_RequestType.Equals(RequestTypes.POST))
{
     // Write POST
 Stream reqStream = _HttpWebRequest.GetRequestStream();
 {
  reqStream.Write(buffer, 0, buffer.Length);
  reqStream.Flush();
  reqStream.Close();
    }
}

And the reponse:

HttpWebResponse httpWebResponse = (HttpWebResponse)_HttpWebRequest.GetResponse();
{
  Stream responseStream = httpWebResponse.GetResponseStream();
  {
    if (_UseGzip)
    {
      if (httpWebResponse.ContentEncoding.ToLower().Contains("gzip"))
      {
        responseStream = new GZipStream(responseStream, CompressionMode.Decompress);
      }
      else
      {
        responseStream = new DeflateStream(responseStream, CompressionMode.Decompress);
      }
    }

    if (responseStream != null)
    {
      StreamReader streamReader = new StreamReader(responseStream);
      {
        try
        {
          _PageContent = streamReader.ReadToEnd();
        }
        finally
        {
          streamReader.Close();
          responseStream.Close();
          httpWebResponse.Close();
        }
      }
    }
    else
    {
      _PageContent = string.Empty;
    }
  }
}
_HttpWebRequest.Abort();

Can anyone see any flaws to why my code is hanging? All streams are being closed, I have set the allowed connections to over 100, I don't understand why this is breaking.

回答1:

This may be due to the fact that you are not disposing of your WebResponse or streams or StreamReaders:

var request = WebRequest.Create(...);
using (var response = request.GetResponse())
{
    using (var responseStream = response.GetResponseStream())
    {
        using (var reader = new StreamReader(responseStream))
        {
            // use the reader
        }
    }
}

回答2:

I had the same problem. I closed (disposed) all streams and the HttpWebResponse correctly with these using blocks. The problem still persisted when i spammed requests which where aborted by ThreadAbortExceptions. Finally it helped to call myWebRequest.Abort() when the ThreadAbortException occurred! Hope this helps.

回答3:

I see that you use:

HttpWebRequest.AutomaticDecompression = DecompressionMethods.GZip;

Along with manual decompression approach:

      if (httpWebResponse.ContentEncoding.ToLower().Contains("gzip"))
      {
        responseStream = new GZipStream(responseStream, CompressionMode.Decompress);
      }
      else
      {
        responseStream = new DeflateStream(responseStream, CompressionMode.Decompress);
      }

Didn't try if it really matters, but i use only manual approach and in similar code, and it works fine. Actually i have hanging problem, but only with one domain, experimenting with properties showed difference.

Oh, and I suspect if you dont use any post data compression, you need to remove content encoding header