question: when a message delivery fails . concode_field_sep NameAddress remote_user concode_elem_sep MessageAgent ma concode_elem_sep Log log concode_elem_sep RegisterAgent ra concode_field_sep void onMaReceivedMessage concode_elem_sep String getRemoteUser concode_elem_sep void unregister concode_elem_sep void unregisterall concode_elem_sep void onUaRegistrationSuccess concode_elem_sep void onUaRegistrationFailure concode_elem_sep void main concode_elem_sep void send concode_elem_sep void printLog concode_elem_sep void printLog concode_elem_sep void onMaDeliverySuccess concode_elem_sep void register
target: void function ( MessageAgent arg0 , NameAddress arg1 , String arg2 , String arg3 ) { }