Custom IQ: error code="503" type="CANCEL" service-unavailable

when i execute the following code

ProviderManager manager = ProviderManager.getInstance();

connection.addPacketListener(invitationListener, new PacketTypeFilter(WhiteboardInvitation.class));

manager.addIQProvider("invitation","http://efycaci.com/client/protocol/whiteboard", new WhiteboardInvitation.Provider());

I got following From Smack debug console

send msg:

<iq id="6vSQ0-386" to="bala@sampath.efycaci.com/onTime" type="get">

  <invitation xmlns="http://efycaci.com/client/protocol/whiteboard"/>

</iq>

received msg:

<iq id="6vSQ0-386" to="sampath@sampath.efycaci.com/onTime" from="bala@sampath.efycaci.com/onTime" type="error">

  <invitation xmlns="http://efycaci.com/client/protocol/whiteboard">

    <accept>false</accept>

  </invitation>

  <error code="503" type="CANCEL">

    <service-unavailable xmlns="urn:ietf:params:xml:ns:xmpp-stanzas"/>

  </error>

</iq>

The custom iq message not received to bala@sampath.efycaci.com/onTime.

I am using Openfire 3.8.3& smack 2.2.2

Please help me to fix this problem