#!/usr/bin/env python3 # Copyright (c) 2014-2017 The Bitcoin Core developers # Distributed under the MIT software license, see the accompanying # file COPYING or http://www.opensource.org/licenses/mit-license.php. """ ZMQ example using python3's asyncio Bitcoin should be started with the command line arguments: bitcoind -testnet -daemon \ -zmqpubrawtx=tcp://127.0.0.1:28332 \ -zmqpubrawblock=tcp://127.0.0.1:28332 \ -zmqpubhashtx=tcp://127.0.0.1:28332 \ -zmqpubhashblock=tcp://127.0.0.1:28332 We use the asyncio library here. `self.handle()` installs itself as a future at the end of the function. Since it never returns with the event loop having an empty stack of futures, this creates an infinite loop. An alternative is to wrap the contents of `handle` inside `while True`. The `@asyncio.coroutine` decorator and the `yield from` syntax found here was introduced in python 3.4 and has been deprecated in favor of the `async` and `await` keywords respectively. A blocking example using python 2.7 can be obtained from the git history: https://github.com/bitcoin/bitcoin/blob/37a7fe9e440b83e2364d5498931253937abe9294/contrib/zmq/zmq_sub.py """ import binascii import asyncio import zmq import zmq.asyncio import signal import struct import sys if not (sys.version_info.major >= 3 and sys.version_info.minor >= 4): print("This example only works with Python 3.4 and greater") sys.exit(1) port = 28332 class ZMQHandler(): def __init__(self): self.loop = zmq.asyncio.install() self.zmqContext = zmq.asyncio.Context() self.zmqSubSocket = self.zmqContext.socket(zmq.SUB) self.zmqSubSocket.setsockopt_string(zmq.SUBSCRIBE, "hashblock") self.zmqSubSocket.setsockopt_string(zmq.SUBSCRIBE, "hashtx") self.zmqSubSocket.setsockopt_string(zmq.SUBSCRIBE, "rawblock") self.zmqSubSocket.setsockopt_string(zmq.SUBSCRIBE, "rawtx") self.zmqSubSocket.connect("tcp://127.0.0.1:%i" % port) @asyncio.coroutine def handle(self) : msg = yield from self.zmqSubSocket.recv_multipart() topic = msg[0] body = msg[1] sequence = "Unknown" if len(msg[-1]) == 4: msgSequence = struct.unpack('<I', msg[-1])[-1] sequence = str(msgSequence) if topic == b"hashblock": print('- HASH BLOCK ('+sequence+') -') print(binascii.hexlify(body)) elif topic == b"hashtx": print('- HASH TX ('+sequence+') -') print(binascii.hexlify(body)) elif topic == b"rawblock": print('- RAW BLOCK HEADER ('+sequence+') -') print(binascii.hexlify(body[:80])) elif topic == b"rawtx": print('- RAW TX ('+sequence+') -') print(binascii.hexlify(body)) # schedule ourselves to receive the next message asyncio.ensure_future(self.handle()) def start(self): self.loop.add_signal_handler(signal.SIGINT, self.stop) self.loop.create_task(self.handle()) self.loop.run_forever() def stop(self): self.loop.stop() self.zmqContext.destroy() daemon = ZMQHandler() daemon.start()