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ACKnowledgements

There is possibility to explicitly acknowledge the receipt of the encrypted packet, by generating the reply of ACK-type which contains the packet identifier.

ACK packets can be generated explicitly by nncp-ack command, or during the tossing procedure if -gen-ack option is specified.

General workflow with acknowledgement is following, assuming that Alice has some outbound packets for Bob:

• Transfer encrypted packets, without deleting them locally:

  alice$ nncp-xfer -keep -tx -node bob /mnt/shared
  

• On Bob’s side retrieve those packets:

  bob$ nncp-xfer -rx /mnt/shared
  

  That will also check if copied packets checksum is not mismatched.

• Create ACK packets of received ones, saving the list of encrypted ACK packets:

  bob$ nncp-ack -node alice 4>acks
  

• Send those newly created packets back to Alice:

  bob$ nncp-xfer [-keep] -tx /mnt/shared
  

• Remove them from outbound spool, because we expect no acknowledgement for them:

  bob$ nncp-rm -node alice -pkt <acks
  

• Get those acknowledgement packets and toss them:

  alice$ nncp-xfer -rx /mnt/shared
  alice$ nncp-toss
  

  Each ACK packet will remove kept corresponding outbound packets, because Bob explicitly confirmed their receipt.

Similarly you can use it with nncp-bundle, but do not forget that by default it does not do checksumming of the packets, so you should either use its -check option, or run nncp-check after.

If you generate ACK packet during the tossing, then the list of ACK packets is saved as empty files directly in the spool. You can remove transferred ACK packets with nncp-rm -ack.