ZMQ topics

A block is connected to the main chain. Fires once per UpdatedBlockTip callback.

Fires for every TransactionAddedToMempool and BlockConnected event; may emit duplicates for the same hash if a tx is re-broadcast or re-mined after a reorg.

Same trigger as hashblock — but the body is the full block, not just its hash. Heavier; only enable if a subscriber actually needs full block bytes (e.g. an indexer that does not have its own bcore peer).

Same trigger as hashtx — body is the full serialized transaction (CTransaction::Serialize). Subscribers can fully decode without round-tripping to JSON-RPC.

Block-connect, block-disconnect, mempool-accept, and mempool-remove events. The body's `event` byte tells subscribers which type. Useful for indexers that need a single ordered event stream rather than the separate hashblock/hashtx topics.

Subscriber examples

import struct
import zmq

ctx = zmq.Context()
sock = ctx.socket(zmq.SUB)
sock.connect("tcp://127.0.0.1:28332")
sock.setsockopt(zmq.SUBSCRIBE, b"hashblock")
while True:
    topic, body, seq_le = sock.recv_multipart()
    (seq,) = struct.unpack("<I", seq_le)
    # block_hash bytes are little-endian; reverse for display hex
    display_hash = body[::-1].hex()
    print(f"seq={seq} {topic.decode()}: {display_hash}")

import zmq from "zeromq";

const sock = new zmq.Subscriber();
sock.connect("tcp://127.0.0.1:28332");
sock.subscribe("rawtx");
for await (const [topic, body, seqLe] of sock) {
  const seq = seqLe.readUInt32LE(0);
  console.log(`seq=${seq} ${topic.toString()} ${body.length} bytes`);
}