Inside Bitcoin

1#!/usr/bin/env python3
2# Copyright (c) 2014-present The Bitcoin Core developers
3# Distributed under the MIT software license, see the accompanying
4# file COPYING or http://www.opensource.org/licenses/mit-license.php.
5
6"""
7    ZMQ example using python3's asyncio
8
9    Bitcoin should be started with the command line arguments:
10        bitcoind -testnet4 -daemon \
11                -zmqpubrawtx=tcp://127.0.0.1:28332 \
12                -zmqpubrawblock=tcp://127.0.0.1:28332 \
13                -zmqpubhashtx=tcp://127.0.0.1:28332 \
14                -zmqpubhashblock=tcp://127.0.0.1:28332 \
15                -zmqpubsequence=tcp://127.0.0.1:28332
16
17    We use the asyncio library here.  `self.handle()` installs itself as a
18    future at the end of the function.  Since it never returns with the event
19    loop having an empty stack of futures, this creates an infinite loop.  An
20    alternative is to wrap the contents of `handle` inside `while True`.
21
22    A blocking example using python 2.7 can be obtained from the git history:
23    https://github.com/bitcoin/bitcoin/blob/37a7fe9e440b83e2364d5498931253937abe9294/contrib/zmq/zmq_sub.py
24"""
25
26import asyncio
27import zmq
28import zmq.asyncio
29import signal
30import struct
31import sys
32
33if (sys.version_info.major, sys.version_info.minor) < (3, 5):
34    print("This example only works with Python 3.5 and greater")
35    sys.exit(1)
36
37port = 28332
38
39class ZMQHandler():
40    def __init__(self):
41        self.loop = asyncio.get_event_loop()
42        self.zmqContext = zmq.asyncio.Context()
43
44        self.zmqSubSocket = self.zmqContext.socket(zmq.SUB)
45        self.zmqSubSocket.setsockopt(zmq.RCVHWM, 0)
46        self.zmqSubSocket.setsockopt_string(zmq.SUBSCRIBE, "hashblock")
47        self.zmqSubSocket.setsockopt_string(zmq.SUBSCRIBE, "hashtx")
48        self.zmqSubSocket.setsockopt_string(zmq.SUBSCRIBE, "rawblock")
49        self.zmqSubSocket.setsockopt_string(zmq.SUBSCRIBE, "rawtx")
50        self.zmqSubSocket.setsockopt_string(zmq.SUBSCRIBE, "sequence")
51        self.zmqSubSocket.connect("tcp://127.0.0.1:%i" % port)
52
53    async def handle(self) :
54        topic, body, seq = await self.zmqSubSocket.recv_multipart()
55        sequence = "Unknown"
56        if len(seq) == 4:
57            sequence = str(struct.unpack('<I', seq)[-1])
58        if topic == b"hashblock":
59            print('- HASH BLOCK ('+sequence+') -')
60            print(body.hex())
61        elif topic == b"hashtx":
62            print('- HASH TX  ('+sequence+') -')
63            print(body.hex())
64        elif topic == b"rawblock":
65            print('- RAW BLOCK HEADER ('+sequence+') -')
66            print(body[:80].hex())
67        elif topic == b"rawtx":
68            print('- RAW TX ('+sequence+') -')
69            print(body.hex())
70        elif topic == b"sequence":
71            hash = body[:32].hex()
72            label = chr(body[32])
73            mempool_sequence = None if len(body) != 32+1+8 else struct.unpack("<Q", body[32+1:])[0]
74            print('- SEQUENCE ('+sequence+') -')
75            print(hash, label, mempool_sequence)
76        # schedule ourselves to receive the next message
77        asyncio.ensure_future(self.handle())
78
79    def start(self):
80        self.loop.add_signal_handler(signal.SIGINT, self.stop)
81        self.loop.create_task(self.handle())
82        self.loop.run_forever()
83
84    def stop(self):
85        self.loop.stop()
86        self.zmqContext.destroy()
87
88daemon = ZMQHandler()
89daemon.start()
90