multinetspeeder/socks_edge.py

from __future__ import annotations

import asyncio
import contextlib
import itertools
import socket
import struct
from dataclasses import dataclass, field
from typing import Dict

from .config import Config, RelayNode
from .protocol import AUTH, STATUS_OK, TCP_CLOSE, TCP_DATA, TCP_OPEN, TCP_STATUS, UDP_RECV, UDP_SEND, Frame, decode_json, encode_json, read_frame, write_frame
from .scheduler import Scheduler

SOCKS_VERSION = 5


async def read_exact(reader: asyncio.StreamReader, size: int) -> bytes:
    return await reader.readexactly(size)


@dataclass(eq=False)
class RelayLink:
    node: RelayNode
    reader: asyncio.StreamReader
    writer: asyncio.StreamWriter
    pump: asyncio.Task | None = None
    closed_event: asyncio.Event = field(default_factory=asyncio.Event)
    maintain_task: asyncio.Task | None = None
    tcp_sessions: Dict[tuple[int, int], "TcpRaceSession"] = field(default_factory=dict)
    udp_server: "UdpAssociateServer | None" = None
    closed: bool = False

    async def start(self) -> None:
        await write_frame(self.writer, Frame(AUTH, 0, 0, 0, 0, encode_json({"token": self.node.token})))
        frame = await read_frame(self.reader)
        if frame.kind != AUTH or frame.packet_id != STATUS_OK:
            raise ConnectionError(f"relay auth failed: {self.node.name}")
        self.closed = False
        self.closed_event.clear()
        self.pump = asyncio.create_task(self._pump())

    async def _pump(self) -> None:
        try:
            while True:
                frame = await read_frame(self.reader)
                key = (frame.session_id, frame.stream_id)
                if frame.kind in (TCP_STATUS, TCP_DATA, TCP_CLOSE):
                    session = self.tcp_sessions.get(key)
                    if session:
                        await session.handle_frame(self, frame)
                elif frame.kind == UDP_RECV and self.udp_server:
                    await self.udp_server.handle_from_relay(frame, self)
        except (asyncio.IncompleteReadError, ConnectionResetError, BrokenPipeError, OSError):
            pass
        except Exception:
            pass
        finally:
            await self.close()

    async def send(self, frame: Frame) -> None:
        if self.closed:
            raise ConnectionError(f"relay closed: {self.node.name}")
        await write_frame(self.writer, frame)

    async def close(self) -> None:
        if self.closed:
            return
        self.closed = True
        self.closed_event.set()
        if self.pump and self.pump is not asyncio.current_task():
            self.pump.cancel()
            with contextlib.suppress(Exception):
                await self.pump
        self.writer.close()
        with contextlib.suppress(Exception):
            await self.writer.wait_closed()


@dataclass
class UdpFlowState:
    flow_id: int
    client_addr: tuple[str, int]
    target_host: str
    target_port: int
    created_at: float
    last_activity: float
    packets_sent: int = 0
    packets_received: int = 0
    duplicate_responses: int = 0
    winner_name: str | None = None
    candidate_names: tuple[str, ...] = ()
    link_streams: dict[str, int] = field(default_factory=dict)
    initialized_links: set[str] = field(default_factory=set)
    direct_sockets: dict[str, socket.socket] = field(default_factory=dict)
    direct_tasks: dict[str, asyncio.Task] = field(default_factory=dict)
    direct_failures: set[str] = field(default_factory=set)
    relay_failures: dict[str, int] = field(default_factory=dict)
    relay_error_seen: set[str] = field(default_factory=set)

    def touch(self, now: float) -> None:
        self.last_activity = now


@dataclass
class TcpRaceSession:
    session_id: int
    stream_id: int
    target_host: str
    target_port: int
    local_reader: asyncio.StreamReader
    local_writer: asyncio.StreamWriter
    links: list[RelayLink]
    warmup_bytes: int
    winning_link: RelayLink | None = None
    winner_name: str | None = None
    opened: int = 0
    open_errors: list[str] = field(default_factory=list)
    uplink_bytes: int = 0
    closed: bool = False
    open_event: asyncio.Event = field(default_factory=asyncio.Event)
    winner_event: asyncio.Event = field(default_factory=asyncio.Event)
    pump_task: asyncio.Task | None = None
    win_counts: Dict[str, int] = field(default_factory=dict)

    async def start(self) -> None:
        meta = encode_json({"host": self.target_host, "port": self.target_port})
        for link in self.links:
            link.tcp_sessions[(self.session_id, self.stream_id)] = self
            await link.send(Frame(TCP_OPEN, self.session_id, self.stream_id, 0, 0, meta))
        await asyncio.wait_for(self.open_event.wait(), timeout=10)
        if self.opened == 0:
            raise ConnectionError(self.open_errors[0] if self.open_errors else "all relays failed")
        self.pump_task = asyncio.create_task(self._pump_local())

    async def _pump_local(self) -> None:
        try:
            while True:
                chunk = await self.local_reader.read(65536)
                if not chunk:
                    break
                self.uplink_bytes += len(chunk)
                if self.winning_link is None and self.uplink_bytes <= self.warmup_bytes:
                    await asyncio.gather(*(link.send(Frame(TCP_DATA, self.session_id, self.stream_id, 0, 0, chunk)) for link in self.links if not link.closed), return_exceptions=True)
                else:
                    if self.winning_link is None:
                        await self.winner_event.wait()
                    if self.winning_link:
                        await self.winning_link.send(Frame(TCP_DATA, self.session_id, self.stream_id, 0, 0, chunk))
        except Exception:
            pass
        finally:
            await self.close()

    async def handle_frame(self, link: RelayLink, frame: Frame) -> None:
        if self.closed:
            return
        if frame.kind == TCP_STATUS:
            if frame.packet_id == STATUS_OK:
                self.opened += 1
            else:
                self.open_errors.append(frame.payload.decode("utf-8", errors="replace"))
            if self.opened > 0 or len(self.open_errors) == len(self.links):
                self.open_event.set()
            return
        if frame.kind == TCP_DATA:
            if self.winning_link is None:
                self.winning_link = link
                self.winner_name = link.node.name
                self.win_counts[link.node.name] = self.win_counts.get(link.node.name, 0) + 1
                node_total = self.win_counts[link.node.name]
                relay_detail = ", ".join(f"{name}={count}" for name, count in sorted(self.win_counts.items())) or "none"
                print(f"[edge] tcp win session={self.session_id} target={self.target_host}:{self.target_port} winner={link.node.name} node_total={node_total} win_breakdown={relay_detail}")
                self.winner_event.set()
                await self._close_losers(except_link=link)
            if link is self.winning_link:
                self.local_writer.write(frame.payload)
                await self.local_writer.drain()
            return
        if frame.kind == TCP_CLOSE:
            if self.winning_link is None:
                self.winning_link = link
                self.winner_event.set()
            if link is self.winning_link:
                await self.close()

    async def _close_losers(self, except_link: RelayLink) -> None:
        await asyncio.gather(*(link.send(Frame(TCP_CLOSE, self.session_id, self.stream_id, 0, 0, b"")) for link in self.links if link is not except_link and not link.closed), return_exceptions=True)

    async def close(self) -> None:
        if self.closed:
            return
        self.closed = True
        if self.pump_task and self.pump_task is not asyncio.current_task():
            self.pump_task.cancel()
            with contextlib.suppress(Exception):
                await self.pump_task
        await asyncio.gather(*(link.send(Frame(TCP_CLOSE, self.session_id, self.stream_id, 0, 0, b"")) for link in self.links if not link.closed), return_exceptions=True)
        for link in self.links:
            link.tcp_sessions.pop((self.session_id, self.stream_id), None)
        self.local_writer.close()
        with contextlib.suppress(Exception):
            await self.local_writer.wait_closed()


class UdpAssociateServer(asyncio.DatagramProtocol):
    def __init__(self, edge: "SocksEdge") -> None:
        self.edge = edge
        self.transport: asyncio.DatagramTransport | None = None
        self.client_addr = None
        self.associate_peer = None
        self.packet_counter = itertools.count(1)
        self.client_flows: dict[tuple[tuple[str, int], str, int], UdpFlowState] = {}
        self.flow_counter = itertools.count(1)
        self.last_summary_at = 0.0
        self.win_counts: Dict[str, int] = {}
        self.relay_error_counts: Dict[str, int] = {}

    def connection_made(self, transport) -> None:
        self.transport = transport

    def register_associate(self, peer) -> None:
        peer_text = f"{peer[0]}:{peer[1]}" if isinstance(peer, tuple) and len(peer) >= 2 else str(peer)
        if self.associate_peer != peer_text:
            print(f"[edge] udp associate peer={peer_text}")
        self.associate_peer = peer_text

    def datagram_received(self, data: bytes, addr) -> None:
        if len(data) < 10:
            return
        if self.client_addr is None:
            self.client_addr = addr
            print(f"[edge] udp client bound addr={addr[0]}:{addr[1]}")
        elif addr != self.client_addr:
            print(f"[edge] udp client rebound old={self.client_addr[0]}:{self.client_addr[1]} new={addr[0]}:{addr[1]}")
            self._reset_client_state(addr)
        host, port, payload = self._parse_socks_udp(data)
        loop = asyncio.get_running_loop()
        now = loop.time()
        flow_key = ((addr[0], addr[1]), host, port)
        flow = self.client_flows.get(flow_key)
        if flow is None:
            flow = UdpFlowState(
                flow_id=next(self.flow_counter),
                client_addr=(addr[0], addr[1]),
                target_host=host,
                target_port=port,
                created_at=now,
                last_activity=now,
            )
            self.client_flows[flow_key] = flow
        flow.touch(now)
        flow.packets_sent += 1
        packet_id = next(self.packet_counter)
        asyncio.create_task(self.edge.forward_udp(flow, payload, packet_id, self))
        self._log_udp_summary()

    def _reset_client_state(self, addr) -> None:
        for flow in list(self.client_flows.values()):
            for task in list(flow.direct_tasks.values()):
                task.cancel()
            for sock in list(flow.direct_sockets.values()):
                with contextlib.suppress(Exception):
                    sock.close()
            for stream_id in list(flow.link_streams.values()):
                self.edge.udp_flow_sessions.pop((flow.flow_id, stream_id), None)
        self.client_flows.clear()
        self.client_addr = addr
        self.win_counts.clear()
        print(f"[edge] udp client bound addr={addr[0]}:{addr[1]}")

    async def handle_from_relay(self, frame: Frame, link: RelayLink) -> None:
        if self.transport is None or self.client_addr is None:
            return
        flow = self.edge.udp_flow_sessions.get((frame.session_id, frame.stream_id))
        if flow is None:
            return
        await self._deliver_flow_packet(flow, frame.packet_id, frame.payload, link.node.name)

    async def handle_from_direct(self, flow: UdpFlowState, path_name: str, payload: bytes) -> None:
        if self.transport is None or self.client_addr is None:
            return
        await self._deliver_flow_packet(flow, 0, payload, path_name)

    async def _deliver_flow_packet(self, flow: UdpFlowState, packet_id: int, payload: bytes, source_name: str) -> None:
        if self.transport is None or self.client_addr is None:
            return
        packet = self._build_socks_udp(flow.target_host, flow.target_port, payload)
        now = asyncio.get_running_loop().time()
        flow.touch(now)
        flow.packets_received += 1
        if flow.winner_name is None:
            flow.winner_name = source_name
            self.win_counts[source_name] = self.win_counts.get(source_name, 0) + 1
            self._log_udp_summary(force=True)
        elif flow.winner_name != source_name:
            flow.duplicate_responses += 1
        if flow.winner_name == source_name:
            self.transport.sendto(packet, self.client_addr)
        self._log_udp_summary()

    def set_flow_candidates(self, flow: UdpFlowState, candidate_names: tuple[str, ...]) -> None:
        if not flow.candidate_names:
            flow.candidate_names = candidate_names

    def note_unsent(self, flow: UdpFlowState, packet_id: int) -> None:
        flow.touch(asyncio.get_running_loop().time())
        flow.relay_failures["unsent"] = flow.relay_failures.get("unsent", 0) + 1
        self._log_udp_summary(force=True)

    def _log_udp_summary(self, force: bool = False) -> None:
        now = asyncio.get_running_loop().time()
        if not force and now - self.last_summary_at < 10:
            return
        self.last_summary_at = now
        active_flows = len(self.client_flows)
        winners = sum(1 for flow in self.client_flows.values() if flow.winner_name)
        packets_sent = sum(flow.packets_sent for flow in self.client_flows.values())
        packets_received = sum(flow.packets_received for flow in self.client_flows.values())
        duplicates = sum(flow.duplicate_responses for flow in self.client_flows.values())
        direct_paths = sum(len(flow.direct_sockets) for flow in self.client_flows.values())
        relay_candidates = sum(len(flow.link_streams) for flow in self.client_flows.values())
        winner_detail = ", ".join(f"{flow.flow_id}:{flow.winner_name}" for flow in self.client_flows.values() if flow.winner_name) or "none"
        relay_errors: list[str] = []
        for flow in self.client_flows.values():
            for name, count in flow.relay_failures.items():
                relay_errors.append(f"{name}={count}")
        relay_error_detail = ", ".join(sorted(relay_errors)) or "none"
        if self.client_addr:
            print(
                f"[edge] udp summary bind={self.client_addr[0]}:{self.client_addr[1]} active_flows={active_flows} "
                f"winner_flows={winners} winner_detail={winner_detail} packets_sent={packets_sent} packets_received={packets_received} dup={duplicates} "
                f"direct_paths={direct_paths} relay_paths={relay_candidates} relay_errors={relay_error_detail}"
            )
        else:
            print(
                f"[edge] udp summary bind=unbound active_flows={active_flows} winner_flows={winners} winner_detail={winner_detail} packets_sent={packets_sent} packets_received={packets_received} dup={duplicates} "
                f"direct_paths={direct_paths} relay_paths={relay_candidates} relay_errors={relay_error_detail}"
            )

    def _parse_socks_udp(self, packet: bytes) -> tuple[str, int, bytes]:
        atyp = packet[3]
        offset = 4
        if atyp == 1:
            host = socket.inet_ntoa(packet[offset:offset + 4])
            offset += 4
        elif atyp == 3:
            size = packet[offset]
            offset += 1
            host = packet[offset:offset + size].decode()
            offset += size
        else:
            raise ValueError("unsupported udp atyp")
        port = struct.unpack("!H", packet[offset:offset + 2])[0]
        offset += 2
        return host, port, packet[offset:]

    def _build_socks_udp(self, host: str, port: int, payload: bytes) -> bytes:
        try:
            addr = socket.inet_aton(host)
            header = b"\x00\x00\x00\x01" + addr + struct.pack("!H", port)
        except OSError:
            raw = host.encode()
            header = b"\x00\x00\x00\x03" + bytes([len(raw)]) + raw + struct.pack("!H", port)
        return header + payload


class SocksEdge:
    def __init__(self, listen_host: str, listen_port: int, config: Config) -> None:
        self.listen_host = listen_host
        self.listen_port = listen_port
        self.config = config
        self.scheduler = Scheduler(config)
        self.links: list[RelayLink] = []
        self.session_ids = itertools.count(1)
        self.udp_stream_ids = itertools.count(1)
        self.udp_flow_sessions: dict[tuple[int, int], UdpFlowState] = {}
        self.udp_server: UdpAssociateServer | None = None

    async def start(self) -> None:
        await self.scheduler.start()
        await self._connect_relays()
        server = await asyncio.start_server(self._accept, self.listen_host, self.listen_port)
        sockets = ", ".join(str(sock.getsockname()) for sock in server.sockets or [])
        print(f"[edge] socks5 listening on {sockets}")
        async with server:
            await server.serve_forever()

    async def _connect_relays(self) -> None:
        loop = asyncio.get_running_loop()
        transport, protocol = await loop.create_datagram_endpoint(lambda: UdpAssociateServer(self), local_addr=(self.listen_host, 0))
        self.udp_server = protocol
        self.udp_transport = transport
        for node in self.config.relays:
            link = RelayLink(node=node, reader=None, writer=None)  # type: ignore[arg-type]
            link.udp_server = protocol
            self.links.append(link)
            link.maintain_task = asyncio.create_task(self._maintain_link(link))

    async def _maintain_link(self, link: RelayLink) -> None:
        backoff = 1.0
        while True:
            try:
                reader, writer = await asyncio.open_connection(link.node.host, link.node.port)
                sock = writer.get_extra_info("socket")
                if sock is not None:
                    with contextlib.suppress(OSError):
                        sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)
                link.reader = reader
                link.writer = writer
                await link.start()
                backoff = 1.0
                await link.closed_event.wait()
            except asyncio.CancelledError:
                raise
            except Exception:
                await asyncio.sleep(backoff)
                backoff = min(10.0, backoff * 2)

    async def _accept(self, reader: asyncio.StreamReader, writer: asyncio.StreamWriter) -> None:
        try:
            peer = writer.get_extra_info("peername")
            host, port, udp_mode = await self._handshake(reader, writer, peer)
            if udp_mode:
                return
            links = self._selected_links()
            session = TcpRaceSession(
                session_id=next(self.session_ids),
                stream_id=0,
                target_host=host,
                target_port=port,
                local_reader=reader,
                local_writer=writer,
                links=links,
                warmup_bytes=self.config.tcp_warmup_bytes,
            )
            await session.start()
        except Exception:
            writer.close()
            with contextlib.suppress(Exception):
                await writer.wait_closed()

    def _selected_links(self) -> list[RelayLink]:
        chosen = {node.name for node in self.scheduler.choose()}
        links = [link for link in self.links if link.node.name in chosen and not link.closed]
        return links or [link for link in self.links if not link.closed][:1]

    def _selected_udp_links(self) -> list[RelayLink]:
        online = [link for link in self.links if not link.closed and link.writer is not None]
        if not online:
            return []
        ordered = sorted(online, key=lambda link: self.scheduler.scores.get(link.node.name).score if link.node.name in self.scheduler.scores else 999999.0)
        return ordered

    def _udp_direct_redundancy_for_target(self, target_host: str) -> int:
        base = self.config.udp_direct_redundancy
        if ":" in target_host and self.config.udp_direct_redundancy_v6 is not None:
            base = self.config.udp_direct_redundancy_v6
        elif ":" not in target_host and self.config.udp_direct_redundancy_v4 is not None:
            base = self.config.udp_direct_redundancy_v4
        return max(1, base)

    async def _ensure_udp_direct_paths(self, flow: UdpFlowState, udp_server: UdpAssociateServer) -> None:
        target_count = self._udp_direct_redundancy_for_target(flow.target_host)
        for index in range(target_count):
            name = f"direct-{index + 1}" if target_count > 1 else "direct"
            if name in flow.direct_sockets or name in flow.direct_failures:
                continue
            try:
                family = socket.AF_INET6 if ":" in flow.target_host else socket.AF_INET
                sock = socket.socket(family, socket.SOCK_DGRAM)
                sock.setblocking(False)
                await asyncio.get_running_loop().sock_connect(sock, (flow.target_host, flow.target_port))
                flow.direct_sockets[name] = sock
                flow.direct_tasks[name] = asyncio.create_task(self._pump_udp_direct(flow, name, sock, udp_server))
            except Exception as exc:
                flow.direct_failures.add(name)
                print(f"[edge] udp direct open error flow={flow.flow_id} path={name} target={flow.target_host}:{flow.target_port} error={exc!r}")

    async def _pump_udp_direct(self, flow: UdpFlowState, path_name: str, sock: socket.socket, udp_server: UdpAssociateServer) -> None:
        loop = asyncio.get_running_loop()
        try:
            while True:
                data = await loop.sock_recv(sock, 65535)
                if not data:
                    break
                await udp_server.handle_from_direct(flow, path_name, data)
        except Exception:
            pass
        finally:
            flow.direct_tasks.pop(path_name, None)
            flow.direct_sockets.pop(path_name, None)
            with contextlib.suppress(Exception):
                sock.close()

    async def forward_udp(self, flow: UdpFlowState, payload: bytes, packet_id: int, udp_server: UdpAssociateServer) -> None:
        await self._ensure_udp_direct_paths(flow, udp_server)
        meta = encode_json({"host": flow.target_host, "port": flow.target_port})
        links = self._selected_udp_links()
        direct_names = tuple(name for name in sorted(flow.direct_sockets))
        relay_names = tuple(link.node.name for link in links)
        candidate_names = direct_names + relay_names
        udp_server.set_flow_candidates(flow, candidate_names)
        if not candidate_names:
            udp_server.note_unsent(flow, packet_id)
            return
        active_direct_names = list(direct_names)
        active_links = links
        if not (self.config.udp_always_broadcast or flow.winner_name is None):
            active_direct_names = [name for name in active_direct_names if name == flow.winner_name]
            active_links = [link for link in active_links if link.node.name == flow.winner_name]
        if not active_direct_names and not active_links:
            if direct_names:
                active_direct_names = [direct_names[0]]
            elif links:
                active_links = links[:1]
        copies = max(1, self.config.udp_redundancy + 1)
        sent_any = False
        for attempt in range(copies):
            for path_name in active_direct_names:
                sock = flow.direct_sockets.get(path_name)
                if sock is None:
                    continue
                try:
                    await asyncio.get_running_loop().sock_sendall(sock, payload)
                    sent_any = True
                except Exception as exc:
                    flow.direct_failures.add(path_name)
                    flow.direct_sockets.pop(path_name, None)
                    task = flow.direct_tasks.pop(path_name, None)
                    if task is not None:
                        task.cancel()
                    with contextlib.suppress(Exception):
                        sock.close()
                    flow.relay_failures[path_name] = flow.relay_failures.get(path_name, 0) + 1
                    if path_name not in flow.relay_error_seen:
                        flow.relay_error_seen.add(path_name)
                        print(
                            f"[edge] udp relay error flow={flow.flow_id} relay={path_name} error={exc!r}"
                        )
            for link in active_links:
                stream_id = flow.link_streams.get(link.node.name)
                if stream_id is None:
                    stream_id = next(self.udp_stream_ids)
                    flow.link_streams[link.node.name] = stream_id
                    self.udp_flow_sessions[(flow.flow_id, stream_id)] = flow
                include_meta = link.node.name not in flow.initialized_links
                body = (meta + payload) if include_meta else payload
                meta_len = len(meta) if include_meta else 0
                try:
                    await link.send(Frame(UDP_SEND, flow.flow_id, stream_id, 0, meta_len, body))
                    flow.initialized_links.add(link.node.name)
                    sent_any = True
                except Exception as exc:
                    flow.link_streams.pop(link.node.name, None)
                    self.udp_flow_sessions.pop((flow.flow_id, stream_id), None)
                    flow.relay_failures[link.node.name] = flow.relay_failures.get(link.node.name, 0) + 1
                    if link.node.name not in flow.relay_error_seen:
                        flow.relay_error_seen.add(link.node.name)
                        print(
                            f"[edge] udp relay error flow={flow.flow_id} relay={link.node.name} error={exc!r}"
                        )
            if attempt + 1 < copies and self.config.udp_copy_interval_ms > 0:
                await asyncio.sleep(self.config.udp_copy_interval_ms / 1000)
        if not sent_any:
            udp_server.note_unsent(flow, packet_id)

    async def _handshake(self, reader: asyncio.StreamReader, writer: asyncio.StreamWriter, peer) -> tuple[str, int, bool]:
        version, methods_len = (await read_exact(reader, 2))
        if version != SOCKS_VERSION:
            raise ValueError("unsupported socks version")
        await read_exact(reader, methods_len)
        writer.write(b"\x05\x00")
        await writer.drain()
        version, command, _, atyp = await read_exact(reader, 4)
        if version != SOCKS_VERSION:
            raise ValueError("unsupported socks version")
        if atyp == 1:
            host = socket.inet_ntoa(await read_exact(reader, 4))
        elif atyp == 3:
            size = (await read_exact(reader, 1))[0]
            host = (await read_exact(reader, size)).decode()
        else:
            raise ValueError("unsupported atyp")
        port = struct.unpack("!H", await read_exact(reader, 2))[0]
        peer_text = f"{peer[0]}:{peer[1]}" if isinstance(peer, tuple) and len(peer) >= 2 else str(peer)
        if command == 1:
            print(f"[edge] socks handshake peer={peer_text} command=connect target={host}:{port}")
            writer.write(b"\x05\x00\x00\x01\x00\x00\x00\x00\x00\x00")
            await writer.drain()
            return host, port, False
        if command == 3 and self.udp_server and self.udp_server.transport:
            bind_host, bind_port = self.udp_server.transport.get_extra_info("sockname")[:2]
            self.udp_server.register_associate(peer)
            print(f"[edge] socks handshake peer={peer_text} command=udp_associate target={host}:{port} bind={bind_host}:{bind_port}")
            writer.write(b"\x05\x00\x00\x01" + socket.inet_aton(bind_host) + struct.pack("!H", bind_port))
            await writer.drain()
            return host, port, True
        raise ValueError("unsupported socks command")