python socks5 proxy server with asyncio (async/await)

server.py

#!/usr/bin/env python3.5
import socket
import asyncio
from struct import pack, unpack


class Client(asyncio.Protocol):
    def connection_made(self, transport):
        self.transport = transport
        self.server_transport = None

    def data_received(self, data):
        # print('recv:', repr(data))
        self.server_transport.write(data)

    def connection_lost(self, *args):
        self.server_transport.close()


class Server(asyncio.Protocol):
    INIT, HOST, DATA = 0, 1, 2

    def connection_made(self, transport):
        print('from:', transport.get_extra_info('peername'))
        self.transport = transport
        self.state = self.INIT

    def connection_lost(self, exc):
        self.transport.close()

    def data_received(self, data):
        # print('send:', repr(data))

        if self.state == self.INIT:
            assert data[0] == 0x05
            self.transport.write(pack('!BB', 0x05, 0x00))  # no auth
            self.state = self.HOST

        elif self.state == self.HOST:
            ver, cmd, rsv, atype = data[:4]
            assert ver == 0x05 and cmd == 0x01

            if atype == 3:    # domain
                length = data[4]
                hostname, nxt = data[5:5+length],  5+length
            elif atype == 1:  # ipv4
                hostname, nxt = socket.inet_ntop(socket.AF_INET, data[4:8]), 8
            elif atype == 4:  # ipv6
                hostname, nxt = socket.inet_ntop(socket.AF_INET6, data[4:20]), 20
            port = unpack('!H', data[nxt:nxt+2])[0]

            print('to:', hostname, port)
            asyncio.ensure_future(self.connect(hostname, port))
            self.state = self.DATA

        elif self.state == self.DATA:
            self.client_transport.write(data)

    async def connect(self, hostname, port):
        loop = asyncio.get_event_loop()
        transport, client = \
            await loop.create_connection(Client, hostname, port)
        client.server_transport = self.transport
        self.client_transport = transport
        hostip, port = transport.get_extra_info('sockname')
        host = unpack("!I", socket.inet_aton(hostip))[0]
        self.transport.write(
            pack('!BBBBIH', 0x05, 0x00, 0x00, 0x01, host, port))

if __name__ == '__main__':
    loop = asyncio.get_event_loop()
    srv = loop.create_server(Server, 'localhost', 8000)
    loop.run_until_complete(srv)
    loop.run_forever()

server2.py

#!/usr/bin/env python3.5
import struct
import asyncio
import socket
from socket import gethostbyname, inet_aton, inet_ntoa


class Client(asyncio.Protocol):
    def connection_made(self, transport):
        self.transport = transport

    def data_received(self, data):
        # print('recv:', repr(data))
        self.server.write(data)

    def connection_lost(self, *args):
        self.server.close()


async def handler(reader, writer):

    async def read(fmt, size):
        return struct.unpack(fmt, await reader.read(size))

    def write(*argv):
        writer.write(struct.pack(*argv))

    loop = asyncio.get_event_loop()
    async def call(func, *argv):
        return await loop.run_in_executor(None, func, *argv)

    ver, meth = await read('BB', 2)
    assert ver == 0x05
    await reader.read(meth)
    write('!BB', 0x05, 0x00)  # no auth
    ver, cmd, rsv, atype = await read('BBBB', 4)
    assert ver == 0x05 and cmd == 0x01

    if atype == 0x03:  # domain
        length = (await read('B', 1))[0]
        hostname = (await read("!{}s".format(length), length))[0]
        hostip = socket.gethostbyname(hostname)
        host = struct.unpack("!I", inet_aton(hostip))[0]
    elif atype == 0x01:  # ipv4
        host = await reader.read(4)
        hostname = isocket.inet_ntop(socket.AF_INET, host)
    elif atype == 0x03:  # ipv6
        host = await reader.read(16)
        hostname = isocket.inet_ntop(socket.AF_INET, host)
    port = (await read('!H', 2))[0]

    print('hostname:', hostname, 'port:', port)
    transport, client = await loop.create_connection(Client, hostname, port)
    client.server = writer
    write('!BBBBIH', 0x05, 0x00, 0x00, 0x01, host, port)

    data = await reader.read(8192)
    while data:
        client.transport.write(data)
        if len(data) < 8192:
            break
        data = await reader.read(8192)

if __name__ == '__main__':
    loop = asyncio.get_event_loop()
    loop.run_until_complete(asyncio.start_server(handler, '0.0.0.0', 8000))
    try:
        loop.run_forever()
    finally:
        loop.close()

when I try to write a socks server with asyncio, I read data_received() will be called when receive some data, I don't know how to write my codes until read your server.py. It is amazing! Your code broaden my horizon! Thanks for your excellent codes.