XMPPConnection Clinet offline problem

when the clinet is online XMPPConnection done well~~ but when the client cut off the network~ the problem appear~ because of the XMPPConnection is not disconnect with the server~ the openfire is still have this connection, the user’s state is still avaliable~ but the truth is that the user is offline. if this client connection is use again~ server replay stream:error(conflict) and then the connection is fail~

so is there any idea to deal with this problem?