"""
:mod:`websockets.protocol` handles WebSocket control and data frames.
See `sections 4 to 8 of RFC 6455`_.
.. _sections 4 to 8 of RFC 6455: http://tools.ietf.org/html/rfc6455#section-4
"""
import asyncio
import codecs
import collections
import enum
import logging
import random
import struct
import sys
import warnings
from typing import (
Any,
AsyncIterable,
AsyncIterator,
Awaitable,
Deque,
Dict,
Iterable,
List,
Optional,
Union,
cast,
)
from .exceptions import (
ConnectionClosed,
ConnectionClosedError,
ConnectionClosedOK,
InvalidState,
PayloadTooBig,
ProtocolError,
)
from .extensions.base import Extension
from .framing import *
from .handshake import *
from .http import Headers
from .typing import Data
__all__ = ["WebSocketCommonProtocol"]
logger = logging.getLogger(__name__)
# A WebSocket connection goes through the following four states, in order:
class State(enum.IntEnum):
CONNECTING, OPEN, CLOSING, CLOSED = range(4)
# In order to ensure consistency, the code always checks the current value of
# WebSocketCommonProtocol.state before assigning a new value and never yields
# between the check and the assignment.
[docs]class WebSocketCommonProtocol(asyncio.Protocol):
"""
:class:`~asyncio.Protocol` subclass implementing the data transfer phase.
Once the WebSocket connection is established, during the data transfer
phase, the protocol is almost symmetrical between the server side and the
client side. :class:`WebSocketCommonProtocol` implements logic that's
shared between servers and clients..
Subclasses such as :class:`~websockets.server.WebSocketServerProtocol` and
:class:`~websockets.client.WebSocketClientProtocol` implement the opening
handshake, which is different between servers and clients.
:class:`WebSocketCommonProtocol` performs four functions:
* It runs a task that stores incoming data frames in a queue and makes
them available with the :meth:`recv` coroutine.
* It sends outgoing data frames with the :meth:`send` coroutine.
* It deals with control frames automatically.
* It performs the closing handshake.
:class:`WebSocketCommonProtocol` supports asynchronous iteration::
async for message in websocket:
await process(message)
The iterator yields incoming messages. It exits normally when the
connection is closed with the close code 1000 (OK) or 1001 (going away).
It raises a :exc:`~websockets.exceptions.ConnectionClosedError` exception
when the connection is closed with any other code.
Once the connection is open, a `Ping frame`_ is sent every
``ping_interval`` seconds. This serves as a keepalive. It helps keeping
the connection open, especially in the presence of proxies with short
timeouts on inactive connections. Set ``ping_interval`` to ``None`` to
disable this behavior.
.. _Ping frame: https://tools.ietf.org/html/rfc6455#section-5.5.2
If the corresponding `Pong frame`_ isn't received within ``ping_timeout``
seconds, the connection is considered unusable and is closed with
code 1011. This ensures that the remote endpoint remains responsive. Set
``ping_timeout`` to ``None`` to disable this behavior.
.. _Pong frame: https://tools.ietf.org/html/rfc6455#section-5.5.3
The ``close_timeout`` parameter defines a maximum wait time in seconds for
completing the closing handshake and terminating the TCP connection.
:meth:`close` completes in at most ``4 * close_timeout`` on the server
side and ``5 * close_timeout`` on the client side.
``close_timeout`` needs to be a parameter of the protocol because
``websockets`` usually calls :meth:`close` implicitly:
- on the server side, when the connection handler terminates,
- on the client side, when exiting the context manager for the connection.
To apply a timeout to any other API, wrap it in :func:`~asyncio.wait_for`.
The ``max_size`` parameter enforces the maximum size for incoming messages
in bytes. The default value is 1 MiB. ``None`` disables the limit. If a
message larger than the maximum size is received, :meth:`recv` will
raise :exc:`~websockets.exceptions.ConnectionClosedError` and the
connection will be closed with code 1009.
The ``max_queue`` parameter sets the maximum length of the queue that
holds incoming messages. The default value is ``32``. ``None`` disables
the limit. Messages are added to an in-memory queue when they're received;
then :meth:`recv` pops from that queue. In order to prevent excessive
memory consumption when messages are received faster than they can be
processed, the queue must be bounded. If the queue fills up, the protocol
stops processing incoming data until :meth:`recv` is called. In this
situation, various receive buffers (at least in ``asyncio`` and in the OS)
will fill up, then the TCP receive window will shrink, slowing down
transmission to avoid packet loss.
Since Python can use up to 4 bytes of memory to represent a single
character, each connection may use up to ``4 * max_size * max_queue``
bytes of memory to store incoming messages. By default, this is 128 MiB.
You may want to lower the limits, depending on your application's
requirements.
The ``read_limit`` argument sets the high-water limit of the buffer for
incoming bytes. The low-water limit is half the high-water limit. The
default value is 64 KiB, half of asyncio's default (based on the current
implementation of :class:`~asyncio.StreamReader`).
The ``write_limit`` argument sets the high-water limit of the buffer for
outgoing bytes. The low-water limit is a quarter of the high-water limit.
The default value is 64 KiB, equal to asyncio's default (based on the
current implementation of ``FlowControlMixin``).
As soon as the HTTP request and response in the opening handshake are
processed:
* the request path is available in the :attr:`path` attribute;
* the request and response HTTP headers are available in the
:attr:`request_headers` and :attr:`response_headers` attributes,
which are :class:`~websockets.http.Headers` instances.
If a subprotocol was negotiated, it's available in the :attr:`subprotocol`
attribute.
Once the connection is closed, the code is available in the
:attr:`close_code` attribute and the reason in :attr:`close_reason`.
All these attributes must be treated as read-only.
"""
# There are only two differences between the client-side and server-side
# behavior: masking the payload and closing the underlying TCP connection.
# Set is_client = True/False and side = "client"/"server" to pick a side.
is_client: bool
side: str = "undefined"
def __init__(
self,
*,
ping_interval: Optional[float] = 20,
ping_timeout: Optional[float] = 20,
close_timeout: Optional[float] = None,
max_size: Optional[int] = 2 ** 20,
max_queue: Optional[int] = 2 ** 5,
read_limit: int = 2 ** 16,
write_limit: int = 2 ** 16,
loop: Optional[asyncio.AbstractEventLoop] = None,
# The following arguments are kept only for backwards compatibility.
host: Optional[str] = None,
port: Optional[int] = None,
secure: Optional[bool] = None,
legacy_recv: bool = False,
timeout: Optional[float] = None,
) -> None:
# Backwards compatibility: close_timeout used to be called timeout.
if timeout is None:
timeout = 10
else:
warnings.warn("rename timeout to close_timeout", DeprecationWarning)
# If both are specified, timeout is ignored.
if close_timeout is None:
close_timeout = timeout
self.ping_interval = ping_interval
self.ping_timeout = ping_timeout
self.close_timeout = close_timeout
self.max_size = max_size
self.max_queue = max_queue
self.read_limit = read_limit
self.write_limit = write_limit
if loop is None:
loop = asyncio.get_event_loop()
self.loop = loop
self._host = host
self._port = port
self._secure = secure
self.legacy_recv = legacy_recv
# Configure read buffer limits. The high-water limit is defined by
# ``self.read_limit``. The ``limit`` argument controls the line length
# limit and half the buffer limit of :class:`~asyncio.StreamReader`.
# That's why it must be set to half of ``self.read_limit``.
self.reader = asyncio.StreamReader(limit=read_limit // 2, loop=loop)
# Copied from asyncio.FlowControlMixin
self._paused = False
self._drain_waiter: Optional[asyncio.Future[None]] = None
self._drain_lock = asyncio.Lock(
loop=loop if sys.version_info[:2] < (3, 8) else None
)
# This class implements the data transfer and closing handshake, which
# are shared between the client-side and the server-side.
# Subclasses implement the opening handshake and, on success, execute
# :meth:`connection_open` to change the state to OPEN.
self.state = State.CONNECTING
logger.debug("%s - state = CONNECTING", self.side)
# HTTP protocol parameters.
self.path: str
self.request_headers: Headers
self.response_headers: Headers
# WebSocket protocol parameters.
self.extensions: List[Extension] = []
self.subprotocol: Optional[str] = None
# The close code and reason are set when receiving a close frame or
# losing the TCP connection.
self.close_code: int
self.close_reason: str
# Completed when the connection state becomes CLOSED. Translates the
# :meth:`connection_lost` callback to a :class:`~asyncio.Future`
# that can be awaited. (Other :class:`~asyncio.Protocol` callbacks are
# translated by ``self.stream_reader``).
self.connection_lost_waiter: asyncio.Future[None] = loop.create_future()
# Queue of received messages.
self.messages: Deque[Data] = collections.deque()
self._pop_message_waiter: Optional[asyncio.Future[None]] = None
self._put_message_waiter: Optional[asyncio.Future[None]] = None
# Protect sending fragmented messages.
self._fragmented_message_waiter: Optional[asyncio.Future[None]] = None
# Mapping of ping IDs to waiters, in chronological order.
self.pings: Dict[bytes, asyncio.Future[None]] = {}
# Task running the data transfer.
self.transfer_data_task: asyncio.Task[None]
# Exception that occurred during data transfer, if any.
self.transfer_data_exc: Optional[BaseException] = None
# Task sending keepalive pings.
self.keepalive_ping_task: asyncio.Task[None]
# Task closing the TCP connection.
self.close_connection_task: asyncio.Task[None]
# Copied from asyncio.FlowControlMixin
async def _drain_helper(self) -> None: # pragma: no cover
if self.connection_lost_waiter.done():
raise ConnectionResetError("Connection lost")
if not self._paused:
return
waiter = self._drain_waiter
assert waiter is None or waiter.cancelled()
waiter = self.loop.create_future()
self._drain_waiter = waiter
await waiter
# Copied from asyncio.StreamWriter
async def _drain(self) -> None: # pragma: no cover
if self.reader is not None:
exc = self.reader.exception()
if exc is not None:
raise exc
if self.transport is not None:
if self.transport.is_closing():
# Yield to the event loop so connection_lost() may be
# called. Without this, _drain_helper() would return
# immediately, and code that calls
# write(...); yield from drain()
# in a loop would never call connection_lost(), so it
# would not see an error when the socket is closed.
await asyncio.sleep(
0, loop=self.loop if sys.version_info[:2] < (3, 8) else None
)
await self._drain_helper()
def connection_open(self) -> None:
"""
Callback when the WebSocket opening handshake completes.
Enter the OPEN state and start the data transfer phase.
"""
# 4.1. The WebSocket Connection is Established.
assert self.state is State.CONNECTING
self.state = State.OPEN
logger.debug("%s - state = OPEN", self.side)
# Start the task that receives incoming WebSocket messages.
self.transfer_data_task = self.loop.create_task(self.transfer_data())
# Start the task that sends pings at regular intervals.
self.keepalive_ping_task = self.loop.create_task(self.keepalive_ping())
# Start the task that eventually closes the TCP connection.
self.close_connection_task = self.loop.create_task(self.close_connection())
@property
def host(self) -> Optional[str]:
alternative = "remote_address" if self.is_client else "local_address"
warnings.warn(f"use {alternative}[0] instead of host", DeprecationWarning)
return self._host
@property
def port(self) -> Optional[int]:
alternative = "remote_address" if self.is_client else "local_address"
warnings.warn(f"use {alternative}[1] instead of port", DeprecationWarning)
return self._port
@property
def secure(self) -> Optional[bool]:
warnings.warn(f"don't use secure", DeprecationWarning)
return self._secure
# Public API
@property
def local_address(self) -> Any:
"""
Local address of the connection.
This is a ``(host, port)`` tuple or ``None`` if the connection hasn't
been established yet.
"""
try:
transport = self.transport
except AttributeError:
return None
else:
return transport.get_extra_info("sockname")
@property
def remote_address(self) -> Any:
"""
Remote address of the connection.
This is a ``(host, port)`` tuple or ``None`` if the connection hasn't
been established yet.
"""
try:
transport = self.transport
except AttributeError:
return None
else:
return transport.get_extra_info("peername")
@property
def open(self) -> bool:
"""
``True`` when the connection is usable.
It may be used to detect disconnections. However, this approach is
discouraged per the EAFP_ principle.
When ``open`` is ``False``, using the connection raises a
:exc:`~websockets.exceptions.ConnectionClosed` exception.
.. _EAFP: https://docs.python.org/3/glossary.html#term-eafp
"""
return self.state is State.OPEN and not self.transfer_data_task.done()
@property
def closed(self) -> bool:
"""
``True`` once the connection is closed.
Be aware that both :attr:`open` and :attr:`closed` are ``False`` during
the opening and closing sequences.
"""
return self.state is State.CLOSED
[docs] async def wait_closed(self) -> None:
"""
Wait until the connection is closed.
This is identical to :attr:`closed`, except it can be awaited.
This can make it easier to handle connection termination, regardless
of its cause, in tasks that interact with the WebSocket connection.
"""
await asyncio.shield(self.connection_lost_waiter)
async def __aiter__(self) -> AsyncIterator[Data]:
"""
Iterate on received messages.
Exit normally when the connection is closed with code 1000 or 1001.
Raise an exception in other cases.
"""
try:
while True:
yield await self.recv()
except ConnectionClosedOK:
return
[docs] async def recv(self) -> Data:
"""
Receive the next message.
Return a :class:`str` for a text frame and :class:`bytes` for a binary
frame.
When the end of the message stream is reached, :meth:`recv` raises
:exc:`~websockets.exceptions.ConnectionClosed`. Specifically, it
raises :exc:`~websockets.exceptions.ConnectionClosedOK` after a normal
connection closure and
:exc:`~websockets.exceptions.ConnectionClosedError` after a protocol
error or a network failure.
.. versionchanged:: 3.0
:meth:`recv` used to return ``None`` instead. Refer to the
changelog for details.
Canceling :meth:`recv` is safe. There's no risk of losing the next
message. The next invocation of :meth:`recv` will return it. This
makes it possible to enforce a timeout by wrapping :meth:`recv` in
:func:`~asyncio.wait_for`.
:raises ~websockets.exceptions.ConnectionClosed: when the
connection is closed
:raises RuntimeError: if two coroutines call :meth:`recv` concurrently
"""
if self._pop_message_waiter is not None:
raise RuntimeError(
"cannot call recv while another coroutine "
"is already waiting for the next message"
)
# Don't await self.ensure_open() here:
# - messages could be available in the queue even if the connection
# is closed;
# - messages could be received before the closing frame even if the
# connection is closing.
# Wait until there's a message in the queue (if necessary) or the
# connection is closed.
while len(self.messages) <= 0:
pop_message_waiter: asyncio.Future[None] = self.loop.create_future()
self._pop_message_waiter = pop_message_waiter
try:
# If asyncio.wait() is canceled, it doesn't cancel
# pop_message_waiter and self.transfer_data_task.
await asyncio.wait(
[pop_message_waiter, self.transfer_data_task],
loop=self.loop if sys.version_info[:2] < (3, 8) else None,
return_when=asyncio.FIRST_COMPLETED,
)
finally:
self._pop_message_waiter = None
# If asyncio.wait(...) exited because self.transfer_data_task
# completed before receiving a new message, raise a suitable
# exception (or return None if legacy_recv is enabled).
if not pop_message_waiter.done():
if self.legacy_recv:
return None # type: ignore
else:
# Wait until the connection is closed to raise
# ConnectionClosed with the correct code and reason.
await self.ensure_open()
# Pop a message from the queue.
message = self.messages.popleft()
# Notify transfer_data().
if self._put_message_waiter is not None:
self._put_message_waiter.set_result(None)
self._put_message_waiter = None
return message
[docs] async def send(
self, message: Union[Data, Iterable[Data], AsyncIterable[Data]]
) -> None:
"""
Send a message.
A string (:class:`str`) is sent as a `Text frame`_. A bytestring or
bytes-like object (:class:`bytes`, :class:`bytearray`, or
:class:`memoryview`) is sent as a `Binary frame`_.
.. _Text frame: https://tools.ietf.org/html/rfc6455#section-5.6
.. _Binary frame: https://tools.ietf.org/html/rfc6455#section-5.6
:meth:`send` also accepts an iterable or an asynchronous iterable of
strings, bytestrings, or bytes-like objects. In that case the message
is fragmented. Each item is treated as a message fragment and sent in
its own frame. All items must be of the same type, or else
:meth:`send` will raise a :exc:`TypeError` and the connection will be
closed.
Canceling :meth:`send` is discouraged. Instead, you should close the
connection with :meth:`close`. Indeed, there only two situations where
:meth:`send` yields control to the event loop:
1. The write buffer is full. If you don't want to wait until enough
data is sent, your only alternative is to close the connection.
:meth:`close` will likely time out then abort the TCP connection.
2. ``message`` is an asynchronous iterator. Stopping in the middle of
a fragmented message will cause a protocol error. Closing the
connection has the same effect.
:raises TypeError: for unsupported inputs
"""
await self.ensure_open()
# While sending a fragmented message, prevent sending other messages
# until all fragments are sent.
while self._fragmented_message_waiter is not None:
await asyncio.shield(self._fragmented_message_waiter)
# Unfragmented message -- this case must be handled first because
# strings and bytes-like objects are iterable.
if isinstance(message, (str, bytes, bytearray, memoryview)):
opcode, data = prepare_data(message)
await self.write_frame(True, opcode, data)
# Fragmented message -- regular iterator.
elif isinstance(message, Iterable):
# Work around https://github.com/python/mypy/issues/6227
message = cast(Iterable[Data], message)
iter_message = iter(message)
try:
message_chunk = next(iter_message)
except StopIteration:
return
opcode, data = prepare_data(message_chunk)
self._fragmented_message_waiter = asyncio.Future()
try:
# First fragment.
await self.write_frame(False, opcode, data)
# Other fragments.
for message_chunk in iter_message:
confirm_opcode, data = prepare_data(message_chunk)
if confirm_opcode != opcode:
raise TypeError("data contains inconsistent types")
await self.write_frame(False, OP_CONT, data)
# Final fragment.
await self.write_frame(True, OP_CONT, b"")
except Exception:
# We're half-way through a fragmented message and we can't
# complete it. This makes the connection unusable.
self.fail_connection(1011)
raise
finally:
self._fragmented_message_waiter.set_result(None)
self._fragmented_message_waiter = None
# Fragmented message -- asynchronous iterator
elif isinstance(message, AsyncIterable):
# aiter_message = aiter(message) without aiter
# https://github.com/python/mypy/issues/5738
aiter_message = type(message).__aiter__(message) # type: ignore
try:
# message_chunk = anext(aiter_message) without anext
# https://github.com/python/mypy/issues/5738
message_chunk = await type(aiter_message).__anext__( # type: ignore
aiter_message
)
except StopAsyncIteration:
return
opcode, data = prepare_data(message_chunk)
self._fragmented_message_waiter = asyncio.Future()
try:
# First fragment.
await self.write_frame(False, opcode, data)
# Other fragments.
# https://github.com/python/mypy/issues/5738
async for message_chunk in aiter_message: # type: ignore
confirm_opcode, data = prepare_data(message_chunk)
if confirm_opcode != opcode:
raise TypeError("data contains inconsistent types")
await self.write_frame(False, OP_CONT, data)
# Final fragment.
await self.write_frame(True, OP_CONT, b"")
except Exception:
# We're half-way through a fragmented message and we can't
# complete it. This makes the connection unusable.
self.fail_connection(1011)
raise
finally:
self._fragmented_message_waiter.set_result(None)
self._fragmented_message_waiter = None
else:
raise TypeError("data must be bytes, str, or iterable")
[docs] async def close(self, code: int = 1000, reason: str = "") -> None:
"""
Perform the closing handshake.
:meth:`close` waits for the other end to complete the handshake and
for the TCP connection to terminate. As a consequence, there's no need
to await :meth:`wait_closed`; :meth:`close` already does it.
:meth:`close` is idempotent: it doesn't do anything once the
connection is closed.
Wrapping :func:`close` in :func:`~asyncio.create_task` is safe, given
that errors during connection termination aren't particularly useful.
Canceling :meth:`close` is discouraged. If it takes too long, you can
set a shorter ``close_timeout``. If you don't want to wait, let the
Python process exit, then the OS will close the TCP connection.
:param code: WebSocket close code
:param reason: WebSocket close reason
"""
try:
await asyncio.wait_for(
self.write_close_frame(serialize_close(code, reason)),
self.close_timeout,
loop=self.loop if sys.version_info[:2] < (3, 8) else None,
)
except asyncio.TimeoutError:
# If the close frame cannot be sent because the send buffers
# are full, the closing handshake won't complete anyway.
# Fail the connection to shut down faster.
self.fail_connection()
# If no close frame is received within the timeout, wait_for() cancels
# the data transfer task and raises TimeoutError.
# If close() is called multiple times concurrently and one of these
# calls hits the timeout, the data transfer task will be cancelled.
# Other calls will receive a CancelledError here.
try:
# If close() is canceled during the wait, self.transfer_data_task
# is canceled before the timeout elapses.
await asyncio.wait_for(
self.transfer_data_task,
self.close_timeout,
loop=self.loop if sys.version_info[:2] < (3, 8) else None,
)
except (asyncio.TimeoutError, asyncio.CancelledError):
pass
# Wait for the close connection task to close the TCP connection.
await asyncio.shield(self.close_connection_task)
[docs] async def ping(self, data: Optional[Data] = None) -> Awaitable[None]:
"""
Send a ping.
Return a :class:`~asyncio.Future` which will be completed when the
corresponding pong is received and which you may ignore if you don't
want to wait.
A ping may serve as a keepalive or as a check that the remote endpoint
received all messages up to this point::
pong_waiter = await ws.ping()
await pong_waiter # only if you want to wait for the pong
By default, the ping contains four random bytes. This payload may be
overridden with the optional ``data`` argument which must be a string
(which will be encoded to UTF-8) or a bytes-like object.
Canceling :meth:`ping` is discouraged. If :meth:`ping` doesn't return
immediately, it means the write buffer is full. If you don't want to
wait, you should close the connection.
Canceling the :class:`~asyncio.Future` returned by :meth:`ping` has no
effect.
"""
await self.ensure_open()
if data is not None:
data = encode_data(data)
# Protect against duplicates if a payload is explicitly set.
if data in self.pings:
raise ValueError("already waiting for a pong with the same data")
# Generate a unique random payload otherwise.
while data is None or data in self.pings:
data = struct.pack("!I", random.getrandbits(32))
self.pings[data] = self.loop.create_future()
await self.write_frame(True, OP_PING, data)
return asyncio.shield(self.pings[data])
[docs] async def pong(self, data: Data = b"") -> None:
"""
Send a pong.
An unsolicited pong may serve as a unidirectional heartbeat.
The payload may be set with the optional ``data`` argument which must
be a string (which will be encoded to UTF-8) or a bytes-like object.
Canceling :meth:`pong` is discouraged for the same reason as
:meth:`ping`.
"""
await self.ensure_open()
data = encode_data(data)
await self.write_frame(True, OP_PONG, data)
# Private methods - no guarantees.
def connection_closed_exc(self) -> ConnectionClosed:
exception: ConnectionClosed
if self.close_code == 1000 or self.close_code == 1001:
exception = ConnectionClosedOK(self.close_code, self.close_reason)
else:
exception = ConnectionClosedError(self.close_code, self.close_reason)
# Chain to the exception that terminated data transfer, if any.
exception.__cause__ = self.transfer_data_exc
return exception
async def ensure_open(self) -> None:
"""
Check that the WebSocket connection is open.
Raise :exc:`~websockets.exceptions.ConnectionClosed` if it isn't.
"""
# Handle cases from most common to least common for performance.
if self.state is State.OPEN:
# If self.transfer_data_task exited without a closing handshake,
# self.close_connection_task may be closing the connection, going
# straight from OPEN to CLOSED.
if self.transfer_data_task.done():
await asyncio.shield(self.close_connection_task)
raise self.connection_closed_exc()
else:
return
if self.state is State.CLOSED:
raise self.connection_closed_exc()
if self.state is State.CLOSING:
# If we started the closing handshake, wait for its completion to
# get the proper close code and reason. self.close_connection_task
# will complete within 4 or 5 * close_timeout after close(). The
# CLOSING state also occurs when failing the connection. In that
# case self.close_connection_task will complete even faster.
await asyncio.shield(self.close_connection_task)
raise self.connection_closed_exc()
# Control may only reach this point in buggy third-party subclasses.
assert self.state is State.CONNECTING
raise InvalidState("WebSocket connection isn't established yet")
async def transfer_data(self) -> None:
"""
Read incoming messages and put them in a queue.
This coroutine runs in a task until the closing handshake is started.
"""
try:
while True:
message = await self.read_message()
# Exit the loop when receiving a close frame.
if message is None:
break
# Wait until there's room in the queue (if necessary).
if self.max_queue is not None:
while len(self.messages) >= self.max_queue:
self._put_message_waiter = self.loop.create_future()
try:
await asyncio.shield(self._put_message_waiter)
finally:
self._put_message_waiter = None
# Put the message in the queue.
self.messages.append(message)
# Notify recv().
if self._pop_message_waiter is not None:
self._pop_message_waiter.set_result(None)
self._pop_message_waiter = None
except asyncio.CancelledError as exc:
self.transfer_data_exc = exc
# If fail_connection() cancels this task, avoid logging the error
# twice and failing the connection again.
raise
except ProtocolError as exc:
self.transfer_data_exc = exc
self.fail_connection(1002)
except (ConnectionError, EOFError) as exc:
# Reading data with self.reader.readexactly may raise:
# - most subclasses of ConnectionError if the TCP connection
# breaks, is reset, or is aborted;
# - IncompleteReadError, a subclass of EOFError, if fewer
# bytes are available than requested.
self.transfer_data_exc = exc
self.fail_connection(1006)
except UnicodeDecodeError as exc:
self.transfer_data_exc = exc
self.fail_connection(1007)
except PayloadTooBig as exc:
self.transfer_data_exc = exc
self.fail_connection(1009)
except Exception as exc:
# This shouldn't happen often because exceptions expected under
# regular circumstances are handled above. If it does, consider
# catching and handling more exceptions.
logger.error("Error in data transfer", exc_info=True)
self.transfer_data_exc = exc
self.fail_connection(1011)
async def read_message(self) -> Optional[Data]:
"""
Read a single message from the connection.
Re-assemble data frames if the message is fragmented.
Return ``None`` when the closing handshake is started.
"""
frame = await self.read_data_frame(max_size=self.max_size)
# A close frame was received.
if frame is None:
return None
if frame.opcode == OP_TEXT:
text = True
elif frame.opcode == OP_BINARY:
text = False
else: # frame.opcode == OP_CONT
raise ProtocolError("unexpected opcode")
# Shortcut for the common case - no fragmentation
if frame.fin:
return frame.data.decode("utf-8") if text else frame.data
# 5.4. Fragmentation
chunks: List[Data] = []
max_size = self.max_size
if text:
decoder_factory = codecs.getincrementaldecoder("utf-8")
decoder = decoder_factory(errors="strict")
if max_size is None:
def append(frame: Frame) -> None:
nonlocal chunks
chunks.append(decoder.decode(frame.data, frame.fin))
else:
def append(frame: Frame) -> None:
nonlocal chunks, max_size
chunks.append(decoder.decode(frame.data, frame.fin))
assert isinstance(max_size, int)
max_size -= len(frame.data)
else:
if max_size is None:
def append(frame: Frame) -> None:
nonlocal chunks
chunks.append(frame.data)
else:
def append(frame: Frame) -> None:
nonlocal chunks, max_size
chunks.append(frame.data)
assert isinstance(max_size, int)
max_size -= len(frame.data)
append(frame)
while not frame.fin:
frame = await self.read_data_frame(max_size=max_size)
if frame is None:
raise ProtocolError("incomplete fragmented message")
if frame.opcode != OP_CONT:
raise ProtocolError("unexpected opcode")
append(frame)
# mypy cannot figure out that chunks have the proper type.
return ("" if text else b"").join(chunks) # type: ignore
async def read_data_frame(self, max_size: Optional[int]) -> Optional[Frame]:
"""
Read a single data frame from the connection.
Process control frames received before the next data frame.
Return ``None`` if a close frame is encountered before any data frame.
"""
# 6.2. Receiving Data
while True:
frame = await self.read_frame(max_size)
# 5.5. Control Frames
if frame.opcode == OP_CLOSE:
# 7.1.5. The WebSocket Connection Close Code
# 7.1.6. The WebSocket Connection Close Reason
self.close_code, self.close_reason = parse_close(frame.data)
try:
# Echo the original data instead of re-serializing it with
# serialize_close() because that fails when the close frame
# is empty and parse_close() synthetizes a 1005 close code.
await self.write_close_frame(frame.data)
except ConnectionClosed:
# It doesn't really matter if the connection was closed
# before we could send back a close frame.
pass
return None
elif frame.opcode == OP_PING:
# Answer pings.
ping_hex = frame.data.hex() or "[empty]"
logger.debug(
"%s - received ping, sending pong: %s", self.side, ping_hex
)
await self.pong(frame.data)
elif frame.opcode == OP_PONG:
# Acknowledge pings on solicited pongs.
if frame.data in self.pings:
logger.debug(
"%s - received solicited pong: %s",
self.side,
frame.data.hex() or "[empty]",
)
# Acknowledge all pings up to the one matching this pong.
ping_id = None
ping_ids = []
for ping_id, ping in self.pings.items():
ping_ids.append(ping_id)
if not ping.done():
ping.set_result(None)
if ping_id == frame.data:
break
else: # pragma: no cover
assert False, "ping_id is in self.pings"
# Remove acknowledged pings from self.pings.
for ping_id in ping_ids:
del self.pings[ping_id]
ping_ids = ping_ids[:-1]
if ping_ids:
pings_hex = ", ".join(
ping_id.hex() or "[empty]" for ping_id in ping_ids
)
plural = "s" if len(ping_ids) > 1 else ""
logger.debug(
"%s - acknowledged previous ping%s: %s",
self.side,
plural,
pings_hex,
)
else:
logger.debug(
"%s - received unsolicited pong: %s",
self.side,
frame.data.hex() or "[empty]",
)
# 5.6. Data Frames
else:
return frame
async def read_frame(self, max_size: Optional[int]) -> Frame:
"""
Read a single frame from the connection.
"""
frame = await Frame.read(
self.reader.readexactly,
mask=not self.is_client,
max_size=max_size,
extensions=self.extensions,
)
logger.debug("%s < %r", self.side, frame)
return frame
async def write_frame(
self, fin: bool, opcode: int, data: bytes, *, _expected_state: int = State.OPEN
) -> None:
# Defensive assertion for protocol compliance.
if self.state is not _expected_state: # pragma: no cover
raise InvalidState(
f"Cannot write to a WebSocket in the {self.state.name} state"
)
frame = Frame(fin, opcode, data)
logger.debug("%s > %r", self.side, frame)
frame.write(
self.transport.write, mask=self.is_client, extensions=self.extensions
)
try:
# drain() cannot be called concurrently by multiple coroutines:
# http://bugs.python.org/issue29930. Remove this lock when no
# version of Python where this bugs exists is supported anymore.
async with self._drain_lock:
# Handle flow control automatically.
await self._drain()
except ConnectionError:
# Terminate the connection if the socket died.
self.fail_connection()
# Wait until the connection is closed to raise ConnectionClosed
# with the correct code and reason.
await self.ensure_open()
async def write_close_frame(self, data: bytes = b"") -> None:
"""
Write a close frame if and only if the connection state is OPEN.
This dedicated coroutine must be used for writing close frames to
ensure that at most one close frame is sent on a given connection.
"""
# Test and set the connection state before sending the close frame to
# avoid sending two frames in case of concurrent calls.
if self.state is State.OPEN:
# 7.1.3. The WebSocket Closing Handshake is Started
self.state = State.CLOSING
logger.debug("%s - state = CLOSING", self.side)
# 7.1.2. Start the WebSocket Closing Handshake
await self.write_frame(True, OP_CLOSE, data, _expected_state=State.CLOSING)
async def keepalive_ping(self) -> None:
"""
Send a Ping frame and wait for a Pong frame at regular intervals.
This coroutine exits when the connection terminates and one of the
following happens:
- :meth:`ping` raises :exc:`ConnectionClosed`, or
- :meth:`close_connection` cancels :attr:`keepalive_ping_task`.
"""
if self.ping_interval is None:
return
try:
while True:
await asyncio.sleep(
self.ping_interval,
loop=self.loop if sys.version_info[:2] < (3, 8) else None,
)
# ping() raises CancelledError if the connection is closed,
# when close_connection() cancels self.keepalive_ping_task.
# ping() raises ConnectionClosed if the connection is lost,
# when connection_lost() calls abort_pings().
ping_waiter = await self.ping()
if self.ping_timeout is not None:
try:
await asyncio.wait_for(
ping_waiter,
self.ping_timeout,
loop=self.loop if sys.version_info[:2] < (3, 8) else None,
)
except asyncio.TimeoutError:
logger.debug("%s ! timed out waiting for pong", self.side)
self.fail_connection(1011)
break
except asyncio.CancelledError:
raise
except ConnectionClosed:
pass
except Exception:
logger.warning("Unexpected exception in keepalive ping task", exc_info=True)
async def close_connection(self) -> None:
"""
7.1.1. Close the WebSocket Connection
When the opening handshake succeeds, :meth:`connection_open` starts
this coroutine in a task. It waits for the data transfer phase to
complete then it closes the TCP connection cleanly.
When the opening handshake fails, :meth:`fail_connection` does the
same. There's no data transfer phase in that case.
"""
try:
# Wait for the data transfer phase to complete.
if hasattr(self, "transfer_data_task"):
try:
await self.transfer_data_task
except asyncio.CancelledError:
pass
# Cancel the keepalive ping task.
if hasattr(self, "keepalive_ping_task"):
self.keepalive_ping_task.cancel()
# A client should wait for a TCP close from the server.
if self.is_client and hasattr(self, "transfer_data_task"):
if await self.wait_for_connection_lost():
return
logger.debug("%s ! timed out waiting for TCP close", self.side)
# Half-close the TCP connection if possible (when there's no TLS).
if self.transport.can_write_eof():
logger.debug("%s x half-closing TCP connection", self.side)
self.transport.write_eof()
if await self.wait_for_connection_lost():
return
logger.debug("%s ! timed out waiting for TCP close", self.side)
finally:
# The try/finally ensures that the transport never remains open,
# even if this coroutine is canceled (for example).
# If connection_lost() was called, the TCP connection is closed.
# However, if TLS is enabled, the transport still needs closing.
# Else asyncio complains: ResourceWarning: unclosed transport.
if self.connection_lost_waiter.done() and self.transport.is_closing():
return
# Close the TCP connection. Buffers are flushed asynchronously.
logger.debug("%s x closing TCP connection", self.side)
self.transport.close()
if await self.wait_for_connection_lost():
return
logger.debug("%s ! timed out waiting for TCP close", self.side)
# Abort the TCP connection. Buffers are discarded.
logger.debug("%s x aborting TCP connection", self.side)
self.transport.abort()
# connection_lost() is called quickly after aborting.
await self.wait_for_connection_lost()
async def wait_for_connection_lost(self) -> bool:
"""
Wait until the TCP connection is closed or ``self.close_timeout`` elapses.
Return ``True`` if the connection is closed and ``False`` otherwise.
"""
if not self.connection_lost_waiter.done():
try:
await asyncio.wait_for(
asyncio.shield(self.connection_lost_waiter),
self.close_timeout,
loop=self.loop if sys.version_info[:2] < (3, 8) else None,
)
except asyncio.TimeoutError:
pass
# Re-check self.connection_lost_waiter.done() synchronously because
# connection_lost() could run between the moment the timeout occurs
# and the moment this coroutine resumes running.
return self.connection_lost_waiter.done()
def fail_connection(self, code: int = 1006, reason: str = "") -> None:
"""
7.1.7. Fail the WebSocket Connection
This requires:
1. Stopping all processing of incoming data, which means cancelling
:attr:`transfer_data_task`. The close code will be 1006 unless a
close frame was received earlier.
2. Sending a close frame with an appropriate code if the opening
handshake succeeded and the other side is likely to process it.
3. Closing the connection. :meth:`close_connection` takes care of
this once :attr:`transfer_data_task` exits after being canceled.
(The specification describes these steps in the opposite order.)
"""
logger.debug(
"%s ! failing %s WebSocket connection with code %d",
self.side,
self.state.name,
code,
)
# Cancel transfer_data_task if the opening handshake succeeded.
# cancel() is idempotent and ignored if the task is done already.
if hasattr(self, "transfer_data_task"):
self.transfer_data_task.cancel()
# Send a close frame when the state is OPEN (a close frame was already
# sent if it's CLOSING), except when failing the connection because of
# an error reading from or writing to the network.
# Don't send a close frame if the connection is broken.
if code != 1006 and self.state is State.OPEN:
frame_data = serialize_close(code, reason)
# Write the close frame without draining the write buffer.
# Keeping fail_connection() synchronous guarantees it can't
# get stuck and simplifies the implementation of the callers.
# Not drainig the write buffer is acceptable in this context.
# This duplicates a few lines of code from write_close_frame()
# and write_frame().
self.state = State.CLOSING
logger.debug("%s - state = CLOSING", self.side)
frame = Frame(True, OP_CLOSE, frame_data)
logger.debug("%s > %r", self.side, frame)
frame.write(
self.transport.write, mask=self.is_client, extensions=self.extensions
)
# Start close_connection_task if the opening handshake didn't succeed.
if not hasattr(self, "close_connection_task"):
self.close_connection_task = self.loop.create_task(self.close_connection())
def abort_pings(self) -> None:
"""
Raise ConnectionClosed in pending keepalive pings.
They'll never receive a pong once the connection is closed.
"""
assert self.state is State.CLOSED
exc = self.connection_closed_exc()
for ping in self.pings.values():
ping.set_exception(exc)
# If the exception is never retrieved, it will be logged when ping
# is garbage-collected. This is confusing for users.
# Given that ping is done (with an exception), canceling it does
# nothing, but it prevents logging the exception.
ping.cancel()
if self.pings:
pings_hex = ", ".join(ping_id.hex() or "[empty]" for ping_id in self.pings)
plural = "s" if len(self.pings) > 1 else ""
logger.debug(
"%s - aborted pending ping%s: %s", self.side, plural, pings_hex
)
# asyncio.Protocol methods
def connection_made(self, transport: asyncio.BaseTransport) -> None:
"""
Configure write buffer limits.
The high-water limit is defined by ``self.write_limit``.
The low-water limit currently defaults to ``self.write_limit // 4`` in
:meth:`~asyncio.WriteTransport.set_write_buffer_limits`, which should
be all right for reasonable use cases of this library.
This is the earliest point where we can get hold of the transport,
which means it's the best point for configuring it.
"""
logger.debug("%s - event = connection_made(%s)", self.side, transport)
transport = cast(asyncio.Transport, transport)
transport.set_write_buffer_limits(self.write_limit)
self.transport = transport
# Copied from asyncio.StreamReaderProtocol
self.reader.set_transport(transport)
def connection_lost(self, exc: Optional[Exception]) -> None:
"""
7.1.4. The WebSocket Connection is Closed.
"""
logger.debug("%s - event = connection_lost(%s)", self.side, exc)
self.state = State.CLOSED
logger.debug("%s - state = CLOSED", self.side)
if not hasattr(self, "close_code"):
self.close_code = 1006
if not hasattr(self, "close_reason"):
self.close_reason = ""
logger.debug(
"%s x code = %d, reason = %s",
self.side,
self.close_code,
self.close_reason or "[no reason]",
)
self.abort_pings()
# If self.connection_lost_waiter isn't pending, that's a bug, because:
# - it's set only here in connection_lost() which is called only once;
# - it must never be canceled.
self.connection_lost_waiter.set_result(None)
if True: # pragma: no cover
# Copied from asyncio.StreamReaderProtocol
if self.reader is not None:
if exc is None:
self.reader.feed_eof()
else:
self.reader.set_exception(exc)
# Copied from asyncio.FlowControlMixin
# Wake up the writer if currently paused.
if not self._paused:
return
waiter = self._drain_waiter
if waiter is None:
return
self._drain_waiter = None
if waiter.done():
return
if exc is None:
waiter.set_result(None)
else:
waiter.set_exception(exc)
def pause_writing(self) -> None: # pragma: no cover
assert not self._paused
self._paused = True
def resume_writing(self) -> None: # pragma: no cover
assert self._paused
self._paused = False
waiter = self._drain_waiter
if waiter is not None:
self._drain_waiter = None
if not waiter.done():
waiter.set_result(None)
def data_received(self, data: bytes) -> None:
logger.debug("%s - event = data_received(<%d bytes>)", self.side, len(data))
self.reader.feed_data(data)
def eof_received(self) -> None:
"""
Close the transport after receiving EOF.
The WebSocket protocol has its own closing handshake: endpoints close
the TCP or TLS connection after sending and receiving a close frame.
As a consequence, they never need to write after receiving EOF, so
there's no reason to keep the transport open by returning ``True``.
Besides, that doesn't work on TLS connections.
"""
logger.debug("%s - event = eof_received()", self.side)
self.reader.feed_eof()
