Authentication against ADFS with WCF hosted on Windows service

Question

I have a wcf service that queries ADFS for SAML token. This is a common snippet from web to query ADFS and get back the SAML token. However it always ends up breaking at the line return channel.Issue(rst); . Error is ID3082: The request scope is not valid or is unsupported. At least at an high level i am not able to figure out whether the error is at the ADFS server end or with the way WCF service is configured or with code. Please help.

public SecurityToken GetSamlToken()
{
    using (var factory = new WSTrustChannelFactory(
        new UserNameWSTrustBinding(SecurityMode.TransportWithMessageCredential),
        new EndpointAddress(new Uri("https://serv/adfs/services/trust/13/usernamemixed"))))
    {
        factory.Credentials.UserName.UserName = "username";
        factory.Credentials.UserName.Password = "password";
        factory.Credentials.ServiceCertificate.Authentication.CertificateValidationMode = X509CertificateValidationMode.None;
        factory.TrustVersion = TrustVersion.WSTrust13;                
        WSTrustChannel channel = null;                
        try
        {
            string KeyType;
            var rst = new RequestSecurityToken
            {
                RequestType = WSTrust13Constants.RequestTypes.Issue,
                AppliesTo = new EndpointAddress("net.tcp://localhost:xxxx/Service1/mex"),                         
                KeyType = Microsoft.IdentityModel.Protocols.WSTrust.WSTrust13Constants.KeyTypes.Bearer,                                        
            };

            channel = (WSTrustChannel)factory.CreateChannel();

            return channel.Issue(rst);
        }
        finally
        {
            if (channel != null)
            {
                channel.Abort();
            }
            factory.Abort();
        }
    }
}

Answer 1

The issue was with the

AppliesTo = new EndpointAddress("net.tcp://localhost:xxxx/Service1/mex")

I replaced it with a relying party uri and it issues me the token. The only issue here being the confusing error messages.