(413) Request Entity Too Large | uploadReadAheadSize

Question

I've written a WCF service with .NET 4.0, which is hosted on my Windows 7 x64 Ultimate system with IIS 7.5. One of the service methods has an 'object' as argument and I'm trying to send a byte[] which contains a picture. As long as the file size of this picture is less then approx. 48KB, all goes well. But if I'm trying to upload a larger picture, the WCF service returns an error: (413) Request Entity Too Large. So ofcourse I've spent 3 hours Googling the error message and every topic I've seen about this subject suggests raising the 'uploadReadAheadSize' property. So what I've done is using the following commands (10485760 = 10MB):

"appcmd.exe set config -section:system.webserver/serverruntime/uploadreadaheadsize: 10485760 /commit:apphost"

"cscript adsutil.vbs set w3svc/<APP_ID>/uploadreadaheadsize 10485760"

I've also used IIS Manager to set the value by opening the site and going to "Configuration Editor" under Management. Unfortunately I'm still getting the Request Entity Too Large error and it's getting really frustrating!

So does anybody know what else I can try to fix this error?

Answer 1

That is not problem of IIS but the problem of WCF. WCF by default limits messages to 65KB to avoid denial of service attack with large messages. Also if you don't use MTOM it sends byte[] to base64 encoded string (33% increase in size) => 48KB * 1,33 = 64KB

To solve this issue you must reconfigure your service to accept larger messages. This issue previously fired 400 Bad Request error but in newer version WCF started to use 413 which is correct status code for this type of error.

You need to set maxReceivedMessageSize in your binding. You can also need to set readerQuotas.

<system.serviceModel>
  <bindings>
    <basicHttpBinding>
      <binding maxReceivedMessageSize="10485760">
        <readerQuotas ... />
      </binding>
    </basicHttpBinding>
  </bindings>  
</system.serviceModel>