Reading “chunked” response with HttpWebResponse

Question

I\'m having trouble reading a \"chunked\" response when using a StreamReader to read the stream returned by GetResponseStream() of a HttpWebResponse:

// resp         


        

Answer 1

After trying a lot of snippets from StackOverflow and Google, ultimately I found this to work the best (assuming you know the data a UTF8 string, if not, you can just keep the byte array and process appropriately):

byte[] data;
var responseStream = response.GetResponseStream();
var reader = new StreamReader(responseStream, Encoding.UTF8);
data = Encoding.UTF8.GetBytes(reader.ReadToEnd());
return Encoding.Default.GetString(data.ToArray());

I found other variations work most of the time, but occasionally truncate the data. I got this snippet from:

https://social.msdn.microsoft.com/Forums/en-US/4f28d99d-9794-434b-8b78-7f9245c099c4/problems-with-httpwebrequest-and-transferencoding-chunked?forum=ncl

Answer 2

I am working on a similar problem. The .net HttpWebRequest and HttpWebRequest handle cookies and redirects automatically but they do not handle chunked content on the response body automatically.

This is perhaps because chunked content may contain more than simple data (i.e.: chunk names, trailing headers).

Simply reading the stream and ignoring the EOF exception will not work as the stream contains more than the desired content. The stream will contain chunks and each chunk begins by declaring its size. If the stream is simply read from beginning to end the final data will contain the chunk meta-data (and in case where it is gziped content it will fail the CRC check when decompressing).

To solve the problem it is necessary to manually parse the stream, removing the chunk size from each chunk (as well as the CR LF delimitors), detecting the final chunk and keeping only the chunk data. There likely is a library out there somewhere that does this, I have not found it yet.

Usefull resources :

http://en.wikipedia.org/wiki/Chunked_transfer_encoding http://tools.ietf.org/html/rfc2616#section-3.6.1

Answer 3

Haven't tried it this with a "chunked" response but would something like this work?

StringBuilder sb = new StringBuilder();
Byte[] buf = new byte[8192];
Stream resStream = response.GetResponseStream();
string tmpString = null;
int count = 0;
do
{
     count = resStream.Read(buf, 0, buf.Length);
     if(count != 0)
     {
          tmpString = Encoding.ASCII.GetString(buf, 0, count);
          sb.Append(tmpString);
     }
}while (count > 0);

Answer 4

I've had the same problem (which is how I ended up here :-). Eventually tracked it down to the fact that the chunked stream wasn't valid - the final zero length chunk was missing. I came up with the following code which handles both valid and invalid chunked streams.

using (StreamReader sr = new StreamReader(response.GetResponseStream(), Encoding.UTF8))
{
    StringBuilder sb = new StringBuilder();

    try
    {
        while (!sr.EndOfStream)
        {
            sb.Append((char)sr.Read());
        }
    }
    catch (System.IO.IOException)
    { }

    string content = sb.ToString();
}