Sends out a packet immediately without synchronization
Sends out a packet with an added sync message.
Sends out a packet with an added sync message. The returned future is completed with the sync message's reply having arrived.
Signalizes that no more messages are sent from the currently committing transaction.
Signalizes that no more messages are sent from the currently committing transaction. The offline server collects these futures, in order to allow an outside process to eventually wait for these to be completed, before closing the OSC file and carrying on. The realtime server just ignores these futures.