C# Simple Web Proxy fails with "Unable to read data from the transport connection"

Question

I'm writting a simple Web Proxy Application(works as IHttpHandler) which basicly exucutes incoming requests and returns response, there's how it looks:

public void ProcessRequest(HttpContext context)
{
   var destinationUrl = GetDestinationUrlFromRequest(context);

   var destinationRequest = WebRequest.Create(destinationUrl);
   CopyHeadersFromTo(context.Request, destinationRequest);
   var destinationResponse = destinationRequest.GetResponse();
   CopyHeadersFromTo(destinationResponse, context.Response);
   var destinationResponseStream = destinationResponse.GetResponseStream();
   using (var streamReader = new StreamReader(destinationResponseStream))
   {
       var result = streamReader.ReadToEnd();
       context.Response.Write(result);
       streamReader.Close();
   }
   context.Response.End();
}

Also, I have another small application, which queries the one from above to get response:

public string QueryData(ICredentials credentials)
{
    var request = (HttpWebRequest) WebRequest.Create("myproxyapp.com/?url=urltoProxy.com");

    request.Method = "POST";
    request.ContentLength = 0;
    request.KeepAlive = false;
    request.ProtocolVersion = HttpVersion.Version10;
    request.ServicePoint.ConnectionLimit = 1;
    if (credentials != null)
    {
        request.Credentials = credentials;
    }
    else
    {
        request.UseDefaultCredentials = true;
    }
    using (var response = (HttpWebResponse) request.GetResponse())
    {
        using (var sr = new StreamReader(response.GetResponseStream()))
        {
            return sr.ReadToEnd();
        }
    }
}

And on sr.ReadToEnd() I keep getting this:

Exception thrown: 'System.IO.IOException' in System.dll

Additional information: Unable to read data from the transport connection: The connection was closed.

Can anyone help with this problem, please?

Answer 1

So I found the problem:

The server that my proxy was querying used Transfer-Encoding: chunked.

In my proxy app I already received unchunked data (that's how HTTP and .NET works).

I was copying all headers from proxy response to the client, even Transfer-Encoding: chunked header.

But, as long as my data was already unchunked, I sent unchunked data to the client.

So, the client received unchunked data and header which says to unchunk it again, which caused the problem!