Getting HTTP 401 Unauthorized error while trying to call Lists.asmx

Question

I am facing this weired issue while trying to call the GetList method of the Lists.asmx web serice from my local dev box. Everything works fine as long as I pass default credentials

listProxy.Credentials = System.Net.CrderntialCache.DefaultCredentials;

But things go wrong as soon as I pass my credentials:

listProxy.Credentials = new System.Net.NetworkCredential("devbox\testuser", "password");  

or

listProxy.Credentials = new System.Net.NetworkCredential("testuser", "password","devbox");  

Note: I have added testuser in the Site Owners group on target SharePoint site collection.

My Development Machine Configuration:

1. Win2k3 SP2
2. No AD installed - devbox is the machine name.
3. Standalone MOSS Installation
4. VS2008

I even tried disabling the loopbackcheck by adding this entry to the registry disableloopbackcheck 1

What can be the possible issue?

Answer 1

I had a similar issue recently and it was because the security binding was incorrect in the app.config/web.config. For me it needed to be

<security mode="TransportCredentialOnly">
    <transport clientCredentialType="Ntlm" />
</security>

rather than the default which was

<security mode="None">
    <transport clientCredentialType="None" proxyCredentialType="None" realm="" />
    <message clientCredentialType="UserName" algorithmSuite="Default" />
</security>

I was using VS2010, not sure if that is relevant but my C# was slightly different to yours as well.

UserGroupService.UserGroupSoapClient client = new UserGroupService.UserGroupSoapClient();
client.ClientCredentials.UserName.UserName = "Username";
client.ClientCredentials.UserName.Password = "Password";
client.ClientCredentials.SupportInteractive = true;
System.Xml.Linq.XElement users = client.GetUserCollectionFromGroup(GroupName.Text);
ResponseXml.Text = users.ToString();