Configuration details are as follows:
Web.config of Wcf service which is hosted.
<basicHttpBinding>
<binding name="HttpBinding_MTOM" messageEncoding="Mtom"
transferMode="Streamed" maxBufferSize="65536"
maxReceivedMessageSize="534773760">
<security mode="None">
<transport clientCredentialType="None" />
</security>
</binding>
</basicHttpBinding>
<services>
<service name="OA.Smart.Services.FileTransferService"
behaviorConfiguration="FileTransferServiceBehavior">
<endpoint address=""
binding="basicHttpBinding"
bindingConfiguration="HttpBinding_MTOM"
contract="OA.Smart.ServiceContract.IFileTransferService">
<identity>
<dns value="localhost" />
</identity>
</endpoint>
<endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange" />
</service>
</services>
<behavior name="FileTransferServiceBehavior">
<serviceMetadata httpGetEnabled="true" />
<serviceDebug includeExceptionDetailInFaults="false" />
</behavior>
I have a smart client application which accesses this WCF service.App.Config is as follows
<bindings>
<basicHttpBinding>
<binding name="BasicHttpBinding_IFileTransferService"
closeTimeout="00:30:00" openTimeout="00:30:
receiveTimeout="00:30:00" sendTimeout="00:30:00"
allowCookies="false" bypassProxyOnLocal="false"
hostNameComparisonMode="StrongWildcard"
maxBufferSize="65536" maxBufferPoolSize="524288"
maxReceivedMessageSize="65536"
messageEncoding="Mtom" textEncoding="utf-8"
transferMode="Streamed" useDefaultWebProxy="true">
<readerQuotas
maxDepth="32" maxStringContentLength="8192"
maxArrayLength="16384" maxBytesPerRead="4096"
maxNameTableCharCount="16384" />
<security mode="None">
<transport clientCredentialType="None" proxyCredentialType="None"
realm="" />
<message clientCredentialType="UserName" algorithmSuite="Default" />
</security>
</binding>
</basicHttpBinding>
</bindings>
<client>
<endpoint
address="http://localhost:4149/OA.Smart.ServiceHost/FileTransferService.svc"
behaviorConfiguration="defaultServiceBehaviour"
binding="basicHttpBinding"
bindingConfiguration="BasicHttpBinding_IFileTransferService"
contract="FileTransferServiceReference.IFileTransferService"
name="BasicHttpBinding_IFileTransferService">
</endpoint>
</client>
<behaviors>
<endpointBehaviors>
<behavior name="defaultServiceBehaviour">
<dataContractSerializer maxItemsInObjectGraph="2147483646" />
</behavior>
</endpointBehaviors>
</behaviors>
With this configuration in place whenever i try to upload my file,It throws as error
System.Net.WebException: The remote server returned an error: (400) Bad Request.
at System.Net.HttpWebRequest.GetResponse()
at System.ServiceModel.Channels.HttpChannelFactory.
HttpRequestChannel.HttpChannelRequest.WaitForReply(TimeSpan timeout)}
However if i change transferMode="Streamed" to "Buffered" it works as expected. I do not understand why it behaves this way. TransferMode of WCF service is streamed, so it should work with streamed.
Please tell me how to make it work with transferMode="Streamed"
Problem was with hosting WCF services.I had hosted them on Cassini(Web server which ships with VS2008) instead of IIS.Cassini does not allow streaming over HTTP.So just using IIS to host WCF services resolved this issue.
You only want to upload files to the server? In that case, have you tried using
transferMode="StreamedRequest"
instead of "Streamed" ?? Any difference?
Also, can you show us the service contract (the interface you're programming against) ?? That might also gives us a clue.
Marc
Related
I have a WCF service, that use tcp for the communication. When I try to transfer a file from the client to the service, if I do that in the same computerm in which the configure file in the client and in the service use the localhost for the url, I have not any problem.
However, if I try to do the same when the client is in other computer in the lan, I get the following exception:
System.TimeoutException: This request operation sent to net.tcp://192.168.1.5:7997/CMMSHost did not receive a reply within the configured timeout (00:01:00). The time allotted to this operation may have been a portion of a longer timeout. This may be because the service is still processing the operation or because the service was unable to send a reply message. Please consider increasing the operation timeout (by casting the channel/proxy to IContextChannel and setting the OperationTimeout property) and ensure that the service is able to connect to the client.
however, if I try to use other actions, such as search information or add registers and any other kind of operation, the application works fine.
So the problem is in the transfer of the file.
In the service I use this configuration:
<endpoint address=""
binding="netTcpBinding"
bindingConfiguration="tcpBinding"
name="NetTcpBindingEndpoint"
contract="GTS.CMMS.Service.IService">
<identity>
<dns value="localhost" />
</identity>
</endpoint>
<endpoint contract="IMetadataExchange" binding="mexTcpBinding" address="net.tcp://localhost:5000/mex" />
</service>
</services>
<behaviors>
<serviceBehaviors>
<behavior name="behaviorConfig">
<!--
<serviceMetadata httpGetEnabled="true" />-->
<!--Necesario para poder enviar excepciones desde el servicio al cliente.-->
<serviceDebug includeExceptionDetailInFaults="true"/>
<serviceThrottling maxConcurrentCalls="100" maxConcurrentSessions="100" />
<serviceMetadata/>
</behavior>
</serviceBehaviors>
</behaviors>
<bindings>
<netTcpBinding>
<binding name="tcpBinding" maxBufferSize="67108864"
maxReceivedMessageSize="67108864" maxBufferPoolSize="67108864"
transferMode="Buffered" closeTimeout="00:00:10"
openTimeout="00:00:10" receiveTimeout="00:20:00"
sendTimeout="00:01:00" maxConnections="100">
<security mode="None"/>
<readerQuotas maxArrayLength="67108864" maxBytesPerRead="67108864" maxStringContentLength="67108864"/>
<reliableSession enabled="true" inactivityTimeout="00:20:00" />
</binding>
</netTcpBinding>
</bindings>
</system.serviceModel>
And in the client:
<configuration>
<system.serviceModel>
<bindings>
<netTcpBinding>
<binding name="NetTcpBinding_IService" closeTimeout="00:01:00"
openTimeout="00:01:00" receiveTimeout="00:10:00" sendTimeout="00:01:00"
transactionFlow="false" transferMode="Buffered" transactionProtocol="OleTransactions"
hostNameComparisonMode="StrongWildcard" listenBacklog="10" maxBufferPoolSize="524288"
maxBufferSize="65536" maxConnections="10" maxReceivedMessageSize="65536">
<readerQuotas maxDepth="32" maxStringContentLength="8192" maxArrayLength="16384"
maxBytesPerRead="4096" maxNameTableCharCount="16384" />
<reliableSession ordered="true" inactivityTimeout="00:20:00"
enabled="true" />
<security mode="None">
<transport clientCredentialType="Windows" protectionLevel="EncryptAndSign" />
<messa
ge clientCredentialType="Windows" />
Thanks.
Is your application is working well for small size file in kbs? if yes then for lager size file use transferMode="Streamed" instead of transferMode="Buffered". You have to change configuration accordingly.
If your application is not working for even smaller files there is a problem with your application.
Build your application and regenerate proxy and try to debug your application.
You can also refer these links
http://www.codeproject.com/Articles/166763/WCF-Streaming-Upload-Download-Files-Over-HTTP
http://www.codeproject.com/Articles/33825/WCF-TCP-based-File-Server
I'm creating a chat application with WCF(using callback contract) and netTcpBinding.
I'm hosting the service as a windows service and accessing it from other computers
via the client application.
The problem that i'm facing now is the clients connection comes to a Fault state after
10 mins which seems to be some kind of timeout that occur.
I already tried increasing the received timeout and send timeout in both service and client but didn't work.
which setting should i change to increase this timeout period and in which application, service or client?
Following are my configuration files,
Service
<system.serviceModel>
<services>
<service behaviorConfiguration="PeerTalk.Service.ChatServiceBehavior"
name="PeerTalk.Service.ChatService">
<endpoint address="" binding="netTcpBinding" bindingConfiguration=""
contract="PeerTalk.Service.ServiceContracts.IChat">
<identity>
<dns value="localhost" />
</identity>
</endpoint>
<endpoint address="mex" binding="mexTcpBinding" bindingConfiguration=""
contract="IMetadataExchange" />
<host>
<baseAddresses>
<add baseAddress="http://localhost:7920/ChatService" />
<add baseAddress="net.tcp://localhost:7921/ChatService" />
</baseAddresses>
</host>
</service>
</services>
<behaviors>
<serviceBehaviors>
<behavior name="PeerTalk.Service.ChatServiceBehavior">
<serviceMetadata httpGetEnabled="false" />
<serviceDebug includeExceptionDetailInFaults="false" />
</behavior>
</serviceBehaviors>
</behaviors>
<bindings>
<netTcpBinding>
<binding name="tcpBinding"
maxBufferSize="67108864"
maxReceivedMessageSize="67108864"
maxBufferPoolSize="67108864"
transferMode="Buffered"
closeTimeout="00:01:00"
openTimeout="00:01:00"
receiveTimeout="00:00:10"
sendTimeout="00:00:10"
maxConnections="100">
<readerQuotas maxDepth="64"
maxStringContentLength="67108864"
maxArrayLength="67108864"
maxBytesPerRead="67108864"
maxNameTableCharCount="16384"/>
<security mode="Transport">
<transport clientCredentialType="Windows" protectionLevel="EncryptAndSign" />
<message clientCredentialType="Windows"/>
</security>
<reliableSession enabled="false" inactivityTimeout="00:01:00"/>
</binding>
</netTcpBinding>
</bindings>
</system.serviceModel>
Client
<system.serviceModel>
<bindings>
<netTcpBinding>
<binding name="NetTcpBinding_IChat" closeTimeout="00:01:00" openTimeout="00:01:00"
receiveTimeout="00:10:00" sendTimeout="00:00:10" transactionFlow="false"
transferMode="Buffered" transactionProtocol="OleTransactions"
hostNameComparisonMode="StrongWildcard" listenBacklog="10" maxBufferPoolSize="67108864"
maxBufferSize="67108864" maxConnections="10" maxReceivedMessageSize="67108864">
<readerQuotas maxDepth="32" maxStringContentLength="67108864"
maxArrayLength="67108864" maxBytesPerRead="67108864" maxNameTableCharCount="16384" />
<reliableSession ordered="true" inactivityTimeout="00:01:00"
enabled="false" />
<security mode="Transport">
<transport clientCredentialType="Windows" protectionLevel="EncryptAndSign" />
<message clientCredentialType="Windows" />
</security>
</binding>
</netTcpBinding>
</bindings>
<client>
<endpoint address="net.tcp://10.10.10.45:7921/ChatService" binding="netTcpBinding"
bindingConfiguration="NetTcpBinding_IChat" contract="PeerTalkService.IChat"
name="NetTcpBinding_IChat">
</endpoint>
</client>
</system.serviceModel>
Thanks.
The timeout in this case is defined by both receiveTimeout in the binding and inactivityTimeout in reliable session which is used for duplex messaging. The correct solution is not increasing timeout but implementing some ping / keep alive messages. The reason is that increasing timeout will keep connections open for failed clients.
Can you post client call sample (service call example). What might happening here is that you are not closing client correctly and you reach maximum sessions on service side.
You must be aware that using net.tcp binding is different than http.
You can use System.ServiceModel performance counters (http://msdn.microsoft.com/en-us/library/ms750527.aspx) and see after 10 minutes what is happening (number of calls outstanding, number of service instances, etc..)
http://dkochnev.blogspot.com/2011/06/wcf-framework-40-monitoring-service.html
I'm working on an WCF service that is secured by Oauth via DotnetOpenAuth.
Somewhere I've got a configuration error that's causing the error "The request for security token could not be satisfied because authentication failed." in my code and I can't see to find a setup that works.
Works fine localhost to localhost but once I put it on my server (not on the domain) it fails from that server to itself or from localhost to the server.
I'm a little worried about some of the other solutions on this site as they seem to disable security. Mostly it's that they don't seem to work for me.
Provider:
<system.serviceModel>
<behaviors>
<serviceBehaviors>
<behavior name="DataApiBehavior">
<serviceMetadata httpGetEnabled="true" />
<serviceDebug includeExceptionDetailInFaults="true" />
<serviceAuthorization serviceAuthorizationManagerType="OAuthServiceProvider.Code.OAuthAuthorizationManager, OAuthServiceProvider" principalPermissionMode="Custom" />
</behavior>
</serviceBehaviors>
</behaviors>
<services>
<service behaviorConfiguration="DataApiBehavior" name="OAuthServiceProvider.DataApi">
<endpoint address="" binding="wsHttpBinding" contract="OAuthServiceProvider.Code.IDataApi">
<identity>
<dns value="localhost" />
</identity>
</endpoint>
<endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange" />
</service>
</services>
<serviceHostingEnvironment>
<baseAddressPrefixFilters>
<add prefix="http://devel.nanaimo.ca/" />
</baseAddressPrefixFilters>
</serviceHostingEnvironment>
</system.serviceModel>
Consumer:
<system.serviceModel>
<bindings>
<wsHttpBinding>
<binding name="WSHttpBinding_IDataApi" 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="65536"
messageEncoding="Text" textEncoding="utf-8" useDefaultWebProxy="true"
allowCookies="false">
<readerQuotas maxDepth="32" maxStringContentLength="8192" maxArrayLength="16384"
maxBytesPerRead="4096" maxNameTableCharCount="16384" />
<reliableSession ordered="true" inactivityTimeout="00:10:00"
enabled="false" />
<security mode="Message">
<transport clientCredentialType="Windows" proxyCredentialType="None"
realm="" />
<message clientCredentialType="Windows" negotiateServiceCredential="true"
algorithmSuite="Default" />
</security>
</binding>
</wsHttpBinding>
</bindings>
<client>
<endpoint address="http://devel.nanaimo.ca/NanaimoProfile/DataApi.svc"
binding="wsHttpBinding" bindingConfiguration="WSHttpBinding_IDataApi"
contract="CodeServiceOauthProvider.IDataApi" name="WSHttpBinding_IDataApi">
<identity>
<dns value="localhost" />
</identity>
</endpoint>
</client>
</system.serviceModel>
Update: Looks like OAuthServiceProvider.Code.OAuthAuthorizationManager Is not being called on live. It's instantiated but CheckAccessCore is never called. I have no idea why yet.
This is just blind shot but AuthorizationManager is used to authorize users and it is called after authentication but you have your service configured with default WsHttpBinding - it uses message security with Windows authentication. Windows authentication doesn't work between computers which are not part of the same domain.
I would start with basicHttpBinding which defaults to no security (no authentication). If it works then you can think about what security do you expect.
I eventually just created a windows username and password with very little rights and hard coded the username into my library. Certificated could have been another answer but I never got them to work.
I would like to use WCF service hosted in IIS (5/6) with integrated windows authentication enabled and anonymous access disabled. I tried to do this by following http://msdn.microsoft.com/en-us/library/ff648431.aspx, but getting an error saying certificate is not installed. But I don't need SSL. I don't have any clients expecting older ASMX services, so I don't need to use basicHttpBinding (and also it is not secure), so I tried to use wsHttpBinding.
How do I get wsHttpBinding with windows authentication to work without SSL? This is such a common requirement, but I couldn't find any solution for this. Can someone post the configuration for the client and the server please? I am using ASP.NET client.
My configuration below. and the exact error message is:
An error occurred while making the HTTP request to
https://mymachine/WCFTest/Service1.svc. This could be due to the fact
that the server certificate is not configured properly with HTTP.SYS
in the HTTPS case. This could also be caused by a mismatch of the
security binding between the client and the server.
I used "svcUtil" utility to generate the proxy class and configuration for the client.
server:
<system.serviceModel>
<bindings>
<wsHttpBinding>
<binding name="wsHttpEndpointBinding">
<security mode="Transport"/>
</binding>
</wsHttpBinding>
</bindings>
<services>
<service behaviorConfiguration="WCFTest.Service1Behavior" name="WCFTest.Service1">
<endpoint address="" binding="wsHttpBinding" bindingConfiguration="wsHttpEndpointBinding" name="wsHttpEndpoint" contract="WCFTest.IService1"/>
</service>
</services>
<behaviors>
<serviceBehaviors>
<behavior name="WCFTest.Service1Behavior">
<!-- 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="false"/>
</behavior>
</serviceBehaviors>
</behaviors>
</system.serviceModel>
client:
<system.serviceModel>
<bindings>
<wsHttpBinding>
<binding name="wsHttpEndpoint" 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="65536"
messageEncoding="Text" textEncoding="utf-8" useDefaultWebProxy="true"
allowCookies="false">
<readerQuotas maxDepth="32" maxStringContentLength="8192" maxArrayLength="16384"
maxBytesPerRead="4096" maxNameTableCharCount="16384" />
<reliableSession ordered="true" inactivityTimeout="00:10:00"
enabled="false" />
<security mode="Transport">
<transport clientCredentialType="Windows" proxyCredentialType="None"
realm="" />
<message clientCredentialType="Windows" negotiateServiceCredential="true"
establishSecurityContext="true" />
</security>
</binding>
</wsHttpBinding>
</bindings>
<client>
<endpoint address="https://mymachine/WCFTest/Service1.svc"
binding="wsHttpBinding" bindingConfiguration="wsHttpEndpoint"
contract="IService1" name="wsHttpEndpoint">
<identity>
<userPrincipalName value="mymachine\ASPNET" />
</identity>
</endpoint>
</client>
</system.serviceModel>
I ended up using basicHttpBinding as explained in the article http://msdn.microsoft.com/en-us/library/ff648505.aspx. posting the config for the client and the server below if anyone is interested. client config is generated using "svcutil".
server config:
<system.serviceModel>
<bindings>
<basicHttpBinding>
<binding name="BasicHttpEndpointBinding">
<security mode="TransportCredentialOnly">
<transport clientCredentialType="Windows" />
</security>
</binding>
</basicHttpBinding>
</bindings>
<services>
<service behaviorConfiguration="WCFTest.Service1Behavior" name="WCFTest.Service1">
<endpoint address="" binding="basicHttpBinding"
bindingConfiguration="BasicHttpEndpointBinding"
name="BasicHttpEndpoint" contract="WCFTest.IService1">
</endpoint>
</service>
</services>
<behaviors>
<serviceBehaviors>
<behavior name="WCFTest.Service1Behavior">
<!-- 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="false"/>
</behavior>
</serviceBehaviors>
</behaviors>
</system.serviceModel>
client config:
<system.serviceModel>
<bindings>
<basicHttpBinding>
<binding name="BasicHttpEndpoint" closeTimeout="00:01:00" openTimeout="00:01:00"
receiveTimeout="00:10:00" sendTimeout="00:01:00" allowCookies="false"
bypassProxyOnLocal="false" hostNameComparisonMode="StrongWildcard"
maxBufferSize="65536" maxBufferPoolSize="524288" maxReceivedMessageSize="65536"
messageEncoding="Text" textEncoding="utf-8" transferMode="Buffered"
useDefaultWebProxy="true">
<readerQuotas maxDepth="32" maxStringContentLength="8192" maxArrayLength="16384"
maxBytesPerRead="4096" maxNameTableCharCount="16384" />
<security mode="TransportCredentialOnly">
<transport clientCredentialType="Windows" proxyCredentialType="None"
realm="" />
<message clientCredentialType="UserName" algorithmSuite="Default" />
</security>
</binding>
</basicHttpBinding>
</bindings>
<client>
<endpoint address="http://machinename/WCFTest/Service1.svc"
binding="basicHttpBinding" bindingConfiguration="BasicHttpEndpoint"
contract="IService1" name="BasicHttpEndpoint" />
</client>
</system.serviceModel>
I have a WCF service hosted on a windows service on my Server1. It also has IIS on this machine. I call the service from a web app and it works fine. But within this service, I have to call another WCF sevice (also hosted on a windows service) located on Server2. The security credentials are set to "Message" and "Username". I have an error like "SOAP protcol negociation failed". It's a problem with my server certificate public key that doesn't seem to be recognise. However, if I call the service on the Server2 from Server1 in a console app, it works fine.
I followed this tutorial to set up my certificates : http://www.codeproject.com/KB/WCF/wcf_certificates.aspx
Here's the config file from my service on Server1 that tries to call the second one :
<endpoint address=""
binding="wsHttpBinding"
contract="Microsoft.ServiceModel.Samples.ITraitement" />
<endpoint address="mex"
binding="mexHttpBinding"
contract="IMetadataExchange" />
</service>
</services>
<client>
<endpoint address="http://Server2:8000/servicemodelsamples/service"
behaviorConfiguration="myClientBehavior" binding="wsHttpBinding"
bindingConfiguration="MybindingCon" contract="Microsoft.ServiceModel.Samples.ICalculator"
name="">
<identity>
<dns value="ODWCertificatServeur" />
</identity>
</endpoint>
</client>
<bindings>
<wsHttpBinding>
<binding name="MybindingCon">
<security mode="Message">
<message clientCredentialType="UserName" />
</security>
</binding>
</wsHttpBinding>
</bindings>
<behaviors>
<serviceBehaviors>
<behavior name="ServiceTraitementBehavior">
<serviceMetadata httpGetEnabled="True"/>
<serviceDebug includeExceptionDetailInFaults="True" />
</behavior>
</serviceBehaviors>
<endpointBehaviors>
<behavior name="myClientBehavior">
<clientCredentials>
<clientCertificate findValue="MachineServiceTraitement" x509FindType="FindBySubjectName" storeLocation="LocalMachine" storeName="My" />
<serviceCertificate>
<authentication certificateValidationMode="ChainTrust" revocationMode="NoCheck"/>
</serviceCertificate>
</clientCredentials>
</behavior>
</endpointBehaviors>
</behaviors>
And here's the config file from the web app that calls the service on Server1 :
<system.serviceModel>
<bindings>
<wsHttpBinding>
<binding name="WSHttpBinding_ITraitement" 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="65536"
messageEncoding="Text" textEncoding="utf-8" useDefaultWebProxy="true"
allowCookies="false">
<readerQuotas maxDepth="32" maxStringContentLength="8192" maxArrayLength="16384"
maxBytesPerRead="4096" maxNameTableCharCount="16384" />
<reliableSession ordered="true" inactivityTimeout="00:10:00"
enabled="false" />
<security mode="Message">
<transport clientCredentialType="Windows" proxyCredentialType="None"
realm="" />
<message clientCredentialType="Windows" negotiateServiceCredential="true"
algorithmSuite="Default" establishSecurityContext="true" />
</security>
</binding>
</wsHttpBinding>
</bindings>
<client>
<endpoint address="http://localhost:8020/ServiceTraitementPC"
binding="wsHttpBinding" bindingConfiguration="WSHttpBinding_ITraitement"
contract="ITraitement" name="WSHttpBinding_ITraitement">
</endpoint>
</client>
Any idea why it works if if I call it in a console app and not from my service ? Maybe it has something to do with the certificateValidationMode="ChainTrust" ?
Well, finally it was just a matter of trusting the issuer of the certificate on the client machine. It was mentioned in the tutorial and I must have missed that step. Still wonder why it worked when calling from a console app, but... anyway, it works fine now.
Thanks !
When you call the service from the console app you are in the security context of the logged in user.
When you call the service from a service running in IIS, with default settings, you are in the security context of a local account NETWORK SERVICE.
The way to fix it is probably to set impersonate=true in the system.web section of your web.config.