The server committed a protocol violation Section ResponseStatusLine ERROR

Question

I have created a program  tried to post a string on a site and I get this error        The server committed a protocol violation  Section ResponseStatusLine     after this line of code   gResponse    HttpWebResponse gRequest GetResponse       How can I fix this exception

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My problem was that I called https endpoint with http

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Try putting this in your app web config    lt system net gt       lt settings gt           lt httpWebRequest useUnsafeHeaderParsing  true    gt       lt  settings gt   lt  system net gt    If this doesn t work you may also try setting the KeepAlive property to false

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A likely cause of this problem is Web Proxy Auto Discovery Protocol  WPAD  configuration on the network  The HTTP request will be transparently sent off to a proxy that can send back a response that the client won t accept or is not configured to accept  Before hacking your code to bits  check that WPAD is not in play  particularly if this just  started happening  out of the blue

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Sometimes this error occurs when UserAgent request parameter is empty  in github com api in my case    Setting this parameter to custom not empty string solved my problem

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I just had the same issue  In my particular case git was removing CR in a http file on check-in  but disregarding the cause  you can follow these steps for debugging the issue  https   technical fail posts 2021-01-26-dotnet-framework-throwing-the-server-committed-a-protocol-violation-section-responsestatusline

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Skype was the main cause of my problem   This error usually occurs when you have set up Visual Studio to debug an existing web application running in IIS rather than the built in ASP NET debug web server  IIS by default listens for web requests on port 80  In this case  another application is already listening for requests on port 80  Typically  the offending application is Skype  which by default takes over listening on ports 80 and 443 when installed  Skype is already occupy the port 80  So IIS is unable to start   To resolve the issue follow the steps   Skype -  Tools -  Options -  Advanced -  Connection   Uncheck  Use port 80 and 443 as alternatives for incoming connections    And as pointed out below perform an IIS reset once done

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Setting expect 100 continue to false and reducing the socket idle time to two seconds resolved the problem for me  ServicePointManager Expect100Continue   false   ServicePointManager  MaxServicePointIdleTime   2000

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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

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I tried to access the Last fm Rest API from behind a proxy and got this famous error       The server committed a protocol violation  Section ResponseStatusLine   After trying some workarounds  only these two worked for me  HttpWebRequest HttpRequestObj   WebRequest Create BaseUrl  as HttpWebRequest  HttpRequestObj ProtocolVersion   HttpVersion Version10    and  HttpWebRequest HttpRequestObj   WebRequest Create BaseUrl  as HttpWebRequest  HttpRequestObj ServicePoint Expect100Continue   false

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I started getting this error from my php JSON REST services  I started getting the error from relativley rare POST uploads after I added ob start  ob gzhandler   to most frequently accessed GET php script   I am able to use just ob start    and everything is fine

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None of the solutions worked for me  so I had to use a WebClient instead of a HttpWebRequest and the issue was no more    I needed to use a CookieContainer  so I used the solution posted by Pavel Savara in this thread - Using CookieContainer with WebClient class  just remove  protected  from this line   private readonly CookieContainer container   new CookieContainer

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See your code and find if you are setting some header with NULL or empty value

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First thing we ve tried was to disable dynamic content compression for IIS   that solved the errors but the error wasn t caused server side and only one client was affected by this   On client side we uninstalled VPN clients  reset internet settings and then reinstalled VPN clients  The error could also be caused by previous antivirus which had firewall  Then we enabled back dynamic content compression and now it works fine as before   Error appeared in custom application which connects to a web service and also at TFS

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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

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In my case the IIS did not have the necessary permissions to access the relevant ASPX path   I gave the IIS user permissions to the relevant directory and all was well

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The culprit in my case was returning a No Content response but defining a response body at the same time  May this answer remind me and maybe others not to return a NoContent response with a body ever again    This behavior is consistent with 10 2 5 204 No Content of the HTTP specification which says      The 204 response MUST NOT include a message-body  and thus is always   terminated by the first empty line after the header fields

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Many solutions talk about a workaround  but not about the actual cause of the error   One possible cause of this error is if the webserver uses an encoding other than ASCII or ISO-8859-1 to output the header response section  The reason to use ISO-8859-1 would be if the Response-Phrase contains extended Latin characters   Another possible cause of this error is if a webserver uses UTF-8 that outputs the byte-order-marker  BOM   For example  the default constant Encoding UTF8 outputs the BOM  and it s easy to forget this   The webpages will work correctly in Firefox and Chrome  but HttpWebRequest will bomb     A quick fix is to change the webserver to use the UTF-8 encoding that doesn t output the BOM  e g  new UTF8Encoding false   which is OK as long as the Response-Phrase only contains ASCII characters  but really it should use ASCII or ISO-8859-1 for the headers  and then UTF-8 or some other encoding for the response

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This was happening for me when I had Skype running on my local machine   As soon as I closed that the exception went away   Idea courtesy of this page

[c#] The server committed a protocol violation. Section=ResponseStatusLine ERROR

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