HttpWebRequestError: The server committed a protocol violation. Section=ResponseHeader Detail=CR must be followed by LF

Question

I have created a sample asp.net application and try to scrape data from my server using httpwebrequest. But some times I got this above error. I have done some searches on g

Answer 1

One way to debug this (and to make sure it is the protocol violation that is causing the problem), is to use Fiddler (Http Web Proxy) and see if the same error occurs. If it doesn't (i.e. Fiddler handled the issue for you) then you should be able to fix it using the UseUnsafeHeaderParsing flag.

If you are looking for a way to set this value programatically see the examples here: http://o2platform.wordpress.com/2010/10/20/dealing-with-the-server-committed-a-protocol-violation-sectionresponsestatusline/

Answer 2

This is certainly a server problem-- the server is not following the HTTP specification and the .NET client is flagging this as a potential problem. "Unsafe" is I think somewhat of a misnomer. There's not really a big security issue here, only non-compliance with the RFC which is bad but unfortunately not rare.

So, as you found in Google, the way to get around the problem is to apply the following configuration change:

<configuration> 
 <system.net> 
  <settings> 
   <httpWebRequest useUnsafeHeaderParsing="true" /> 
  </settings> 
 </system.net> 
</configuration>

Answer 3

You may want to check the content of your headers. Try adding the following, as suggested by this link:

Accept: text/html, application/xhtml+xml, */*

Answer 4

Another possibility: when doing a POST, the server responds with a 100 continue in an incorrect way.

This solved the problem for me:

request.ServicePoint.Expect100Continue = false;