C# – Large WCF web service request failing with (400) HTTP Bad Request


I've encountered this apparently common problem and have been unable to resolve it.

If I call my WCF web service with a relatively small number of items in an array parameter (I've tested up to 50), everything is fine.

However if I call the web service with 500 items, I get the Bad Request error.

Interestingly, I've run Wireshark on the server and it appears that the request isn't even hitting the server – the 400 error is being generated on the client side.

The exception is:

System.ServiceModel.ProtocolException: The remote server returned an unexpected response: (400) Bad Request. —> System.Net.WebException: The remote server returned an error: (400) Bad Request.

The system.serviceModel section of my client config file is:

            <binding name="WSHttpBinding_IMyService" closeTimeout="00:01:00"
                openTimeout="00:01:00" receiveTimeout="00:10:00" sendTimeout="00:01:00"
                bypassProxyOnLocal="false" transactionFlow="false" hostNameComparisonMode="StrongWildcard"
                maxBufferPoolSize="524288" maxReceivedMessageSize="2147483647"
                messageEncoding="Text" textEncoding="utf-8" useDefaultWebProxy="true"
                <readerQuotas maxDepth="32" maxStringContentLength="8192" maxArrayLength="2147483647"
                    maxBytesPerRead="4096" maxNameTableCharCount="16384" />
                <reliableSession ordered="true" inactivityTimeout="00:10:00"
                    enabled="false" />
                <security mode="None">
                    <transport clientCredentialType="Windows" proxyCredentialType="None"
                        realm="" />
                    <message clientCredentialType="Windows" negotiateServiceCredential="true"
                        establishSecurityContext="true" />
        <endpoint address="http://serviceserver/MyService.svc"
            binding="wsHttpBinding" bindingConfiguration="WSHttpBinding_IMyService"
            contract="SmsSendingService.IMyService" name="WSHttpBinding_IMyService" />

On the server side, my web.config file has the following system.serviceModel section:

        <service name="MyService.MyService" behaviorConfiguration="MyService.MyServiceBehaviour" >
            <endpoint address="" binding="wsHttpBinding" bindingConfiguration="MyService.MyServiceBinding" contract="MyService.IMyService">
            <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange"/>
        <binding name="MyService.MyServiceBinding">
          <security mode="None"></security>
            <behavior name="MyService.MyServiceBehaviour">
                <!-- To avoid disclosing metadata information, set the value below to false and remove the metadata endpoint above before deployment -->
                <serviceMetadata httpGetEnabled="true"/>
                <!-- To receive exception details in faults for debugging purposes, set the value below to true.  Set to false before deployment to avoid disclosing exception information -->
                <serviceDebug includeExceptionDetailInFaults="true"/>

I've looked at a fairly large number of answers to this question with no success.

Can anyone help me with this?

Best Solution

Try setting maxReceivedMessageSize on the server too, e.g. to 4MB:

<binding name="MyService.MyServiceBinding" maxReceivedMessageSize="4194304">

The main reason the default (65535 I believe) is so low is to reduce the risk of Denial of Service (DoS) attacks. You need to set it bigger than the maximum request size on the server, and the maximum response size on the client. If you're in an Intranet environment, the risk of DoS attacks is probably low, so it's probably safe to use a value much higher than you expect to need.

By the way a couple of tips for troubleshooting problems connecting to WCF services:

  • Enable tracing on the server as described in this MSDN article.

  • Use an HTTP debugging tool such as Fiddler on the client to inspect the HTTP traffic.

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