6. Publisher

The publisher is for discovering about new confirmed blocks and unconfirmed (but validated) transactions.

In your config file, you should see something similar to:

# Valid values: "enabled" / "disabled"
# Next 2 values ignored if publisher equals "disabled"
publisher = "disabled"
block-publish = "tcp://*:9093"
tx-publish = "tcp://*:9094"

Set publisher to “enabled”. The worker will now make 2 PUBSUB ports available. In the example above, blocks arrive on port 9093, and transactions on port 9094.

TODO: Obelisk should send the last update when a client connects. ZeroMQ has this feature, but I have to investigate how to implement this [genjix].

6.1. Confirmed Blocks

Fields Type(Size)
height uint32(4)
hash sha256 hash(32)
header block header(80)
number of transactions uint32(4)
transaction hashes sha256 hash(variable number of fields of 32 bytes)

The hash can be used as a checksum by hashing the block_header. The transactions can be verified by checking the merkle root within the block header.

The client should be buffering unconfirmed transactions, and only requesting the transactions which they need but don’t have in their buffer from the server.

6.2. Unconfirmed Validated Transactions

Fields Type(Size)
hash sha256 hash(32)
transaction data

Currently Obelisk doesn’t send an update when you first connect, but this will be changed. You should be able to handle being giving the last update (for both blocks and transactions) when you first connect.

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