How to obtain a kerberos service ticket via GSS-API?

Does anyone know how to get a service ticket from the Key Distribution Center (KDC) using the Java GSS-API?

I have a thick-client-application that first authenticates via JAAS using the Krb5LoginModule to fetch the TGT from the ticket cache (background: Windows e.g. uses a kerberos implementation and stores the ticket granting ticket in a secure memory area). From the LoginManager I get the Subject object which contains the TGT. Now I hoped when I create a specific GSSCredential object for my service, the service ticket will be put into the Subject's private credentials as well (I've read so somewhere in the web). So I have tried the following:

// Exception handling ommitted
LoginContext lc = new LoginContext("HelloEjbClient", new DialogCallbackHandler());
lc.login()
Subject.doAs(lc.getSubject(), new PrivilegedAction() {

    public Object run() {
        GSSManager manager = GSSManager.getInstance();
        GSSName clientName = manager.createName("clientUser", GSSName.NT_USER_NAME);
        GSSCredential clientCreds = manager.createCredential(clientName, 8 * 3600, createKerberosOid(), GSSCredential.INITIATE_ONLY);

        GSSName serverName = manager.createName("myService@localhost", GSSName.NT_HOSTBASED_SERVICE);
        manager.createCredential(serverName, GSSCredential.INDEFINITE_LIFETIME, createKerberosOid(), GSSCredential.INITIATE_ONLY);
        return null;
    }

    private Oid createKerberosOid() {
        return new Oid("1.2.840.113554.1.2.2");
    }

});

Unfortunately I get a GSSException: No valid credentials provided (Mechanism level: Failed to find any Kerberos tgt).