C# HttpListener Response + GZipStream

Question

I use HttpListener for my own http server (I do not use IIS). I want to compress my OutputStream by GZip compression:

byte[] refBuffer = Encoding.UTF8.GetBytes(...some data source...);

var varByteStream = new MemoryStream(refBuffer);

System.IO.Compression.GZipStream refGZipStream = new GZipStream(varByteStream, CompressionMode.Compress, false);

refGZipStream.BaseStream.CopyTo(refHttpListenerContext.Response.OutputStream);

refHttpListenerContext.Response.AddHeader("Content-Encoding", "gzip");

But I getting error in Chrome:

ERR_CONTENT_DECODING_FAILED

If I remove AddHeader, then it works, but the size of response is not seems being compressed. What am I doing wrong?

It's impossible for something to not be compressed because of a header, given that you're actually explicitly writing the content as compressed. Are you sure Chrome isn't just giving you the *decompressed* size of the file? — Ry-, Sep 15 '11 at 22:36
@minitech, good questions!!! I'm trying to check actual size of traffic. — Edward83, Sep 15 '11 at 22:41

score 11 · Accepted Answer · answered Sep 16 '11 at 01:57

The problem is that your transfer is going in the wrong direction. What you want to do is attach the GZipStream to the Response.OutputStream and then call CopyTo on the MemoryStream, passing in the GZipStream, like so:

refHttpListenerContext.Response.AddHeader("Content-Encoding", "gzip"); 

byte[] refBuffer = Encoding.UTF8.GetBytes(...some data source...); 

var varByteStream = new MemoryStream(refBuffer); 

System.IO.Compression.GZipStream refGZipStream = new GZipStream(refHttpListenerContext.Response.OutputStream, CompressionMode.Compress, false); 

varByteStream.CopyTo(refGZipStream); 
refGZipStream.Flush();

score 4 · Answer 2 · answered Jun 06 '12 at 23:59

The first problem (as mentioned by Brent M Spell) is the wrong position of the header. The second is that you don't use properly the GZipStream. This stream requires a "top" stream to write to, meaning an empty stream (you fill it with your buffer). Having an empty "top" stream then all you have to do is to write on GZipStream your buffer. As a result the memory stream will be filled by the compressed content. So you need something like:

byte[] buffer = ....;

using (var ms = new MemoryStream())
{
    using (var zip = new GZipStream(ms, CompressionMode.Compress, true))
    zip.Write(buffer, 0, buffer.Length);
    buffer = ms.ToArray();
}

response.AddHeader("Content-Encoding", "gzip");
response.ContentLength64 = buffer.Length;

response.OutputStream.Write(buffer, 0, buffer.Length);

score 0 · Answer 3 · edited May 23 '17 at 12:31

0

Hopeful this might help, they discuss how to get GZIP working.

Sockets in C#: How to get the response stream?

edited May 23 '17 at 12:31

Community

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answered Sep 16 '11 at 05:11

Nickz

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C# HttpListener Response + GZipStream

3 Answers3