Can not catch message event

In my Flex App, when i use anonymous login, and use _conn.send(msg) to send message to spark, spark get what i send, but Flex debuger do not trace message event, when i use spark to send msg back to my App, i get nothing, neither the msg nor the msg event

anybody help? THX

You should set presence before. You see the usage in the code here:

Thanks, i have solved my problem