ネットワークハンドシェイクと接続

### ネットワークハンドシェイク
ネットワークハンドシェイクの方法
– AがBに接続するためにversionメッセージを送信
– Bがversionメッセージを受信し、verackメッセージで応答し、自身のversionメッセージを送信
※verackはボディー（ペイロード）が無く、メッセージ名だけのメッセージ
– Aはversionメッセージとverackメッセージを受信し、verackメッセージを送信
– Bはverackメッセージを受信し、通信を継続
ハンドシェイク後に通信できる
不正なトランザクションまたはブロックを送信した場合、通信が禁止または切断される可能性がある

### ネットワークへの接続

import socket
from network immport NetworkEnvelop, VersionMessage
host = ''
port = 18333
socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
socket.connect((host, port))
stream = socket.makefile('rb', None)
version = VersionMessage()
envelop = NetworkEnvelop(version.command, version.serialize())
socket.sendall(envelop.serialize())
while True:
    new_message = NetworkEnvelope.parse(stream)
    print(new_message)

class VerAckMessage:
    command = b'verack'

    def __init__(self):
        pass
    
    @classmethod
    def parse(cls, s):
        return cls()
    
    def serialize(self):
        return b''

SimpleNone

class SimpleNone:

    def __init__(self, host, port=None, testnet=False, logging=False):
        if port is None:
            if testnet:
                port = 18333
            else:
                port = 8333
        self.testnet = testnet
        self.logging = logging
        self.socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.socket.connect((host, port))
        self.stream = self.socket.makefile('rb', None)
    
    def send(self, message):
        envelope = NetworkEnvelop(
            message.command, message.serialize(), testnet=self.testnet)
        if self.logging:
            print('sending: {}'.format(envelop))
        self.socket.sendall(envelope.serialize())
    
    def read(self):
        envelop = NetworkEnvelop.parse(self.stream, testnet=self.testnet)
        if self.logging:
            print('receiving: {}'.format(envelop))
        return envelope

    def wait_for(self, *message_classes):
        command = None
        command_to_class = {m.command: m for m in message_classes}
        while command not in command_to_class.keys():
            envelope = self.read()
            command = envelop.command
            if command == VersionMessage.command:
                self.send(VerAckMessage())
            elif command == PingMessage.command:
                self.send(PongMessage(envelope.payload))
        return command_to_class[command].parse(envelope.stream())

他のNodeとのハンドシェイク

from network import SimpleNode, VersionMessage
node = SimpleNone('', testnet=True)
version = VersionMessage()
node.send(version)
verack_received = False
version_received = False
while not verack_received and not version_received:
    message = node.wait_for(VersionMessage, VerArckMessage)
    if message.command == VerArckMessage.command:
        verack_received = True
    else:
        version_received = True
        node.sed(VerAckMessage())

handshake

   def handshake(self):
        version = VersionMessage()
        node.send(version)
        self.wait_for(VerAckMessage)