ios XMPPFramewok can not receive Iq when i send query for roster

ios XMPPFramewok can not receive Iq when i send query for roster

when i send roster query like:
NSXMLElement *query = [NSXMLElement elementWithName:@"query"
xmlns:@"jabber:iq:roster"];
NSXMLElement *iq = [NSXMLElement elementWithName:@"iq"];
XMPPJID *myJID = self.xmppStream.myJID;
[iq addAttributeWithName:@"from" stringValue:myJID.description];
[iq addAttributeWithName:@"to" stringValue:myJID.domain];
[iq addAttributeWithName:@"id" stringValue:@"0101"];
[iq addAttributeWithName:@"type" stringValue:@"get"];
[iq addChild:query];
[[self xmppStream] sendElement:iq];
xmppStream can not recevie IQ in method didReceiveIQ:
- (BOOL)xmppStream:(XMPPStream *)sender didReceiveIQ:(XMPPIQ *)iq;
is something i need to config ?