Attempts to advance the current delivery. Advances it to the next delivery if one exists, else null.
The behaviour of this method is different for senders and receivers.
@return true if it can advance, false if it cannot
TODO document the meaning of the return value more fully. Currently Senderimpl only returns false if there is no current delivery
See Implementation
Attempts to advance the current delivery. Advances it to the next delivery if one exists, else null.
The behaviour of this method is different for senders and receivers.
@return true if it can advance, false if it cannot
TODO document the meaning of the return value more fully. Currently Senderimpl only returns false if there is no current delivery