Python functions to create an arbitrary Bitcoin peer-to-peer message, and a version message.

msgUtils.py

magic = 0xd9b4bef9

def makeMessage(magic, command, payload):
    checksum = hashlib.sha256(hashlib.sha256(payload).digest()).digest()[0:4]
    return struct.pack('L12sL4s', magic, command, len(payload), checksum) + payload

def getVersionMsg():
    version = 60002
    services = 1
    timestamp = int(time.time())
    addr_me = utils.netaddr(socket.inet_aton("127.0.0.1"), 8333)
    addr_you = utils.netaddr(socket.inet_aton("127.0.0.1"), 8333)
    nonce = random.getrandbits(64)
    sub_version_num = utils.varstr('')
    start_height = 0

    payload = struct.pack('<LQQ26s26sQsL', version, services, timestamp, addr_me,
        addr_you, nonce, sub_version_num, start_height)
    return makeMessage(magic, 'version', payload)