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Editorial Team
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Asked: 2026-05-18T09:53:01+00:00

I’m getting the The underlying connection was closed: The connection was closed unexpectedly. error

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I’m getting the “The underlying connection was closed: The connection was closed unexpectedly.” error while trying to POST using the HttpWebRequest class on the production server, on my dev machine it works fine.

I originally tried using the WebClient class but I switched to the HttpWebRequest to try some of the suggestions I found while researching the issue (such as setting KeepAlive to false, PreAuthenticate true
and ProtocolVersion to 1.0).

Since it’s only happening on the production server, i’m guessing that it might have something to do with IIS.

Here’s my code

        HttpWebRequest HttpWReq =
        (HttpWebRequest)WebRequest.Create(webURL);

        ASCIIEncoding encoding=new ASCIIEncoding();
        Byte[] postbytes = Encoding.ASCII.GetBytes(data);

        HttpWReq.Headers.Add("Authorization",
                  String.Format("Basic {0}", authstring));
        HttpWReq.KeepAlive = false;
        HttpWReq.PreAuthenticate = true;  
        HttpWReq.Credentials = CredentialCache.DefaultCredentials;
        HttpWReq.UseDefaultCredentials = true;
        HttpWReq.ProtocolVersion = HttpVersion.Version10;


        HttpWReq.Method = "POST";
        HttpWReq.ContentType = "application/x-www-form-urlencoded";
        HttpWReq.ContentLength = postbytes.Length;

        Stream newStream = HttpWReq.GetRequestStream();
        newStream.Write(postbytes, 0, postbytes.Length);
        newStream.Close();

And the code I originally tried using the WebClient class

  /*  WebClient client = new WebClient();
    client.Headers.Add("Authorization",
              String.Format("Basic {0}", authstring));
    client.Headers.Add("Content-Type",
                       "application/x-www-form-urlencoded");
    client.UseDefaultCredentials = true;
    System.Net.ServicePointManager.Expect100Continue =  false;

     Byte[] postbytes = Encoding.ASCII.GetBytes(data);

    byte[] resp = client.UploadData(webURL, "POST", postbytes); */

Thanks, Any help would be appreciated.

EDIT:

Using fidler to examine the header I got this info

POST [MyWebSite] HTTP/1.1
Accept: image/gif, image/jpeg, image/pjpeg, image/pjpeg, application/x-shockwave-            flash, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, application/x-ms-application, application/x-ms-xbap, application/vnd.ms-xpsdocument, application/xaml+xml, */*
Referer: [MyWebSite]
Accept-Language: en-us
User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; Trident/4.0; GTB6.5; InfoPath.2; .NET CLR 2.0.50727; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729; .NET CLR 1.1.4322)
Content-Type: application/x-www-form-urlencoded
Accept-Encoding: gzip, deflate
Host: [MyHost]
Content-Length: 188
Connection: Keep-Alive
Pragma: no-cache
Cookie: __utma=62854692.1254171006.1276438746.1289273298.1289317993.21; __utmz=62854692.1277743505.3.3.utmcsr=google|utmccn=(organic)|utmcmd=organic|utmctr=yeled; ASPSESSIONIDQQQRCRAT=ANNHGGNBNOFNFCLHPBEJIMLC

__VIEWSTATE=%2FwEPDwUKMjA0OTM4MTAwNGRktZi0IsIUo6MOCYTxun8p8Po4AWeTtipGZ4L9%2FkY3KZU%3D&__EVENTVALIDATION=%2FwEWAgLHhsXtBwK14deQBbiFCpWBnsp%2BicqBy%2FNXAkhuVDX9WF1jZayRuTgPc3Ov&btnTest=Test

EDIT2

If set the Target Framework (I used a new project for testing) to 2.0 (I didn’t test every version of the framework) it works. I’m guessing that .net handles the security differently in .net 4.0. This isn’t a solution, but I’m hoping somebody could use that info to help me resolve this.

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1 Answer

  1. Editorial Team

    It appears to be a permissions issue. If I change the application pool’s account on IIS from ASP.net to NTService it then posts correctly. I’m going to try and find out which specific permission it needs and see if I can grant that to the asp.net account.

    UPDATE

    I’m not sure what exactly did it, but after changing some of the write permissions for the user account that’s running on the server and restarting it, it is now working.

    In the end I was able to use the WebClient wrapper class.

        WebClient client = new WebClient();

    client.Headers.Add("Authorization",
                          String.Format("Basic {0}", authstring));
    client.Headers.Add("Content-Type",
                       "application/x-www-form-urlencoded");
    client.UseDefaultCredentials = true;

    byte[] resp = client.UploadData(url, "POST", postbytes);
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