Feature-not-implemented(501) MultiUserChat.getJoinedRooms

hi everyone,

when l use MultiUserChat to get joined rooms l get problems it saying feature-not-implemented(501),

the logcat loged the follow information:

11-09 07:49:17.582: W/System.err(1782): feature-not-implemented(501)

11-09 07:49:17.582: W/System.err(1782): at org.jivesoftware.smackx.ServiceDiscoveryManager.discoverItems(ServiceDiscoveryM anager.java:610)

11-09 07:49:17.592: W/System.err(1782): at org.jivesoftware.smackx.muc.MultiUserChat.getJoinedRooms(MultiUserChat.java:221 )

11-09 07:49:17.592: W/System.err(1782): at com.ichat.activity.RoomManager.getJoinedRooms(RoomManager.java:103)

11-09 07:49:17.602: W/System.err(1782): at com.ichat.activity.RoomManager.init(RoomManager.java:96)

11-09 07:49:17.602: W/System.err(1782): at com.ichat.activity.RoomManager.onCreate(RoomManager.java:38)

l am a new in asmack develop,can anyone give me a hand to solve this problem or give me a correct example in MultiUserChat.getJoinedRooms?

l am very happy to accept any advice for this problem. note: l am chinese ,not good at english