from __future__ import annotations import contextlib import logging import random import socket import struct import threading import uuid from types import TracebackType from typing import Any, Iterable, Iterator, Mapping from ..exceptions import ( ConcurrencyError, ConnectionClosed, ConnectionClosedOK, ProtocolError, ) from ..frames import DATA_OPCODES, BytesLike, CloseCode, Frame, Opcode from ..http11 import Request, Response from ..protocol import CLOSED, OPEN, Event, Protocol, State from ..typing import Data, LoggerLike, Subprotocol from .messages import Assembler from .utils import Deadline __all__ = ["Connection"] class Connection: """ :mod:`threading` implementation of a WebSocket connection. :class:`Connection` provides APIs shared between WebSocket servers and clients. You shouldn't use it directly. Instead, use :class:`~websockets.sync.client.ClientConnection` or :class:`~websockets.sync.server.ServerConnection`. """ recv_bufsize = 65536 def __init__( self, socket: socket.socket, protocol: Protocol, *, close_timeout: float | None = 10, ) -> None: self.socket = socket self.protocol = protocol self.close_timeout = close_timeout # Inject reference to this instance in the protocol's logger. self.protocol.logger = logging.LoggerAdapter( self.protocol.logger, {"websocket": self}, ) # Copy attributes from the protocol for convenience. self.id: uuid.UUID = self.protocol.id """Unique identifier of the connection. Useful in logs.""" self.logger: LoggerLike = self.protocol.logger """Logger for this connection.""" self.debug = self.protocol.debug # HTTP handshake request and response. self.request: Request | None = None """Opening handshake request.""" self.response: Response | None = None """Opening handshake response.""" # Mutex serializing interactions with the protocol. self.protocol_mutex = threading.Lock() # Assembler turning frames into messages and serializing reads. self.recv_messages = Assembler() # Whether we are busy sending a fragmented message. self.send_in_progress = False # Deadline for the closing handshake. self.close_deadline: Deadline | None = None # Mapping of ping IDs to pong waiters, in chronological order. self.ping_waiters: dict[bytes, threading.Event] = {} # Receiving events from the socket. This thread is marked as daemon to # allow creating a connection in a non-daemon thread and using it in a # daemon thread. This mustn't prevent the interpreter from exiting. self.recv_events_thread = threading.Thread( target=self.recv_events, daemon=True, ) self.recv_events_thread.start() # Exception raised in recv_events, to be chained to ConnectionClosed # in the user thread in order to show why the TCP connection dropped. self.recv_exc: BaseException | None = None # Public attributes @property def local_address(self) -> Any: """ Local address of the connection. For IPv4 connections, this is a ``(host, port)`` tuple. The format of the address depends on the address family. See :meth:`~socket.socket.getsockname`. """ return self.socket.getsockname() @property def remote_address(self) -> Any: """ Remote address of the connection. For IPv4 connections, this is a ``(host, port)`` tuple. The format of the address depends on the address family. See :meth:`~socket.socket.getpeername`. """ return self.socket.getpeername() @property def subprotocol(self) -> Subprotocol | None: """ Subprotocol negotiated during the opening handshake. :obj:`None` if no subprotocol was negotiated. """ return self.protocol.subprotocol # Public methods def __enter__(self) -> Connection: return self def __exit__( self, exc_type: type[BaseException] | None, exc_value: BaseException | None, traceback: TracebackType | None, ) -> None: if exc_type is None: self.close() else: self.close(CloseCode.INTERNAL_ERROR) def __iter__(self) -> Iterator[Data]: """ Iterate on incoming messages. The iterator calls :meth:`recv` and yields messages in an infinite loop. It exits when the connection is closed normally. It raises a :exc:`~websockets.exceptions.ConnectionClosedError` exception after a protocol error or a network failure. """ try: while True: yield self.recv() except ConnectionClosedOK: return def recv(self, timeout: float | None = None) -> Data: """ Receive the next message. When the connection is closed, :meth:`recv` raises :exc:`~websockets.exceptions.ConnectionClosed`. Specifically, it raises :exc:`~websockets.exceptions.ConnectionClosedOK` after a normal closure and :exc:`~websockets.exceptions.ConnectionClosedError` after a protocol error or a network failure. This is how you detect the end of the message stream. If ``timeout`` is :obj:`None`, block until a message is received. If ``timeout`` is set and no message is received within ``timeout`` seconds, raise :exc:`TimeoutError`. Set ``timeout`` to ``0`` to check if a message was already received. If the message is fragmented, wait until all fragments are received, reassemble them, and return the whole message. Returns: A string (:class:`str`) for a Text_ frame or a bytestring (:class:`bytes`) for a Binary_ frame. .. _Text: https://datatracker.ietf.org/doc/html/rfc6455#section-5.6 .. _Binary: https://datatracker.ietf.org/doc/html/rfc6455#section-5.6 Raises: ConnectionClosed: When the connection is closed. ConcurrencyError: If two threads call :meth:`recv` or :meth:`recv_streaming` concurrently. """ try: return self.recv_messages.get(timeout) except EOFError: # Wait for the protocol state to be CLOSED before accessing close_exc. self.recv_events_thread.join() raise self.protocol.close_exc from self.recv_exc except ConcurrencyError: raise ConcurrencyError( "cannot call recv while another thread " "is already running recv or recv_streaming" ) from None def recv_streaming(self) -> Iterator[Data]: """ Receive the next message frame by frame. If the message is fragmented, yield each fragment as it is received. The iterator must be fully consumed, or else the connection will become unusable. :meth:`recv_streaming` raises the same exceptions as :meth:`recv`. Returns: An iterator of strings (:class:`str`) for a Text_ frame or bytestrings (:class:`bytes`) for a Binary_ frame. .. _Text: https://datatracker.ietf.org/doc/html/rfc6455#section-5.6 .. _Binary: https://datatracker.ietf.org/doc/html/rfc6455#section-5.6 Raises: ConnectionClosed: When the connection is closed. ConcurrencyError: If two threads call :meth:`recv` or :meth:`recv_streaming` concurrently. """ try: for frame in self.recv_messages.get_iter(): yield frame except EOFError: # Wait for the protocol state to be CLOSED before accessing close_exc. self.recv_events_thread.join() raise self.protocol.close_exc from self.recv_exc except ConcurrencyError: raise ConcurrencyError( "cannot call recv_streaming while another thread " "is already running recv or recv_streaming" ) from None def send(self, message: Data | Iterable[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: https://datatracker.ietf.org/doc/html/rfc6455#section-5.6 .. _Binary: https://datatracker.ietf.org/doc/html/rfc6455#section-5.6 :meth:`send` also accepts an iterable of strings, bytestrings, or bytes-like objects to enable fragmentation_. 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. .. _fragmentation: https://datatracker.ietf.org/doc/html/rfc6455#section-5.4 :meth:`send` rejects dict-like objects because this is often an error. (If you really want to send the keys of a dict-like object as fragments, call its :meth:`~dict.keys` method and pass the result to :meth:`send`.) When the connection is closed, :meth:`send` 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. Args: message: Message to send. Raises: ConnectionClosed: When the connection is closed. ConcurrencyError: If the connection is sending a fragmented message. TypeError: If ``message`` doesn't have a supported type. """ # Unfragmented message -- this case must be handled first because # strings and bytes-like objects are iterable. if isinstance(message, str): with self.send_context(): if self.send_in_progress: raise ConcurrencyError( "cannot call send while another thread " "is already running send" ) self.protocol.send_text(message.encode()) elif isinstance(message, BytesLike): with self.send_context(): if self.send_in_progress: raise ConcurrencyError( "cannot call send while another thread " "is already running send" ) self.protocol.send_binary(message) # Catch a common mistake -- passing a dict to send(). elif isinstance(message, Mapping): raise TypeError("data is a dict-like object") # Fragmented message -- regular iterator. elif isinstance(message, Iterable): chunks = iter(message) try: chunk = next(chunks) except StopIteration: return try: # First fragment. if isinstance(chunk, str): text = True with self.send_context(): if self.send_in_progress: raise ConcurrencyError( "cannot call send while another thread " "is already running send" ) self.send_in_progress = True self.protocol.send_text( chunk.encode(), fin=False, ) elif isinstance(chunk, BytesLike): text = False with self.send_context(): if self.send_in_progress: raise ConcurrencyError( "cannot call send while another thread " "is already running send" ) self.send_in_progress = True self.protocol.send_binary( chunk, fin=False, ) else: raise TypeError("data iterable must contain bytes or str") # Other fragments for chunk in chunks: if isinstance(chunk, str) and text: with self.send_context(): assert self.send_in_progress self.protocol.send_continuation( chunk.encode(), fin=False, ) elif isinstance(chunk, BytesLike) and not text: with self.send_context(): assert self.send_in_progress self.protocol.send_continuation( chunk, fin=False, ) else: raise TypeError("data iterable must contain uniform types") # Final fragment. with self.send_context(): self.protocol.send_continuation(b"", fin=True) self.send_in_progress = False except ConcurrencyError: # We didn't start sending a fragmented message. # The connection is still usable. raise except Exception: # We're half-way through a fragmented message and we can't # complete it. This makes the connection unusable. with self.send_context(): self.protocol.fail( CloseCode.INTERNAL_ERROR, "error in fragmented message", ) raise else: raise TypeError("data must be str, bytes, or iterable") def close(self, code: int = CloseCode.NORMAL_CLOSURE, reason: str = "") -> None: """ Perform the closing handshake. :meth:`close` waits for the other end to complete the handshake, for the TCP connection to terminate, and for all incoming messages to be read with :meth:`recv`. :meth:`close` is idempotent: it doesn't do anything once the connection is closed. Args: code: WebSocket close code. reason: WebSocket close reason. """ try: # The context manager takes care of waiting for the TCP connection # to terminate after calling a method that sends a close frame. with self.send_context(): if self.send_in_progress: self.protocol.fail( CloseCode.INTERNAL_ERROR, "close during fragmented message", ) else: self.protocol.send_close(code, reason) except ConnectionClosed: # Ignore ConnectionClosed exceptions raised from send_context(). # They mean that the connection is closed, which was the goal. pass def ping(self, data: Data | None = None) -> threading.Event: """ Send a Ping_. .. _Ping: https://datatracker.ietf.org/doc/html/rfc6455#section-5.5.2 A ping may serve as a keepalive or as a check that the remote endpoint received all messages up to this point Args: data: Payload of the ping. A :class:`str` will be encoded to UTF-8. If ``data`` is :obj:`None`, the payload is four random bytes. Returns: An event that will be set when the corresponding pong is received. You can ignore it if you don't intend to wait. :: pong_event = ws.ping() pong_event.wait() # only if you want to wait for the pong Raises: ConnectionClosed: When the connection is closed. ConcurrencyError: If another ping was sent with the same data and the corresponding pong wasn't received yet. """ if isinstance(data, BytesLike): data = bytes(data) elif isinstance(data, str): data = data.encode() elif data is not None: raise TypeError("data must be str or bytes-like") with self.send_context(): # Protect against duplicates if a payload is explicitly set. if data in self.ping_waiters: raise ConcurrencyError("already waiting for a pong with the same data") # Generate a unique random payload otherwise. while data is None or data in self.ping_waiters: data = struct.pack("!I", random.getrandbits(32)) pong_waiter = threading.Event() self.ping_waiters[data] = pong_waiter self.protocol.send_ping(data) return pong_waiter def pong(self, data: Data = b"") -> None: """ Send a Pong_. .. _Pong: https://datatracker.ietf.org/doc/html/rfc6455#section-5.5.3 An unsolicited pong may serve as a unidirectional heartbeat. Args: data: Payload of the pong. A :class:`str` will be encoded to UTF-8. Raises: ConnectionClosed: When the connection is closed. """ if isinstance(data, BytesLike): data = bytes(data) elif isinstance(data, str): data = data.encode() else: raise TypeError("data must be str or bytes-like") with self.send_context(): self.protocol.send_pong(data) # Private methods def process_event(self, event: Event) -> None: """ Process one incoming event. This method is overridden in subclasses to handle the handshake. """ assert isinstance(event, Frame) if event.opcode in DATA_OPCODES: self.recv_messages.put(event) if event.opcode is Opcode.PONG: self.acknowledge_pings(bytes(event.data)) def acknowledge_pings(self, data: bytes) -> None: """ Acknowledge pings when receiving a pong. """ with self.protocol_mutex: # Ignore unsolicited pong. if data not in self.ping_waiters: return # Sending a pong for only the most recent ping is legal. # Acknowledge all previous pings too in that case. ping_id = None ping_ids = [] for ping_id, ping in self.ping_waiters.items(): ping_ids.append(ping_id) ping.set() if ping_id == data: break else: raise AssertionError("solicited pong not found in pings") # Remove acknowledged pings from self.ping_waiters. for ping_id in ping_ids: del self.ping_waiters[ping_id] def recv_events(self) -> None: """ Read incoming data from the socket and process events. Run this method in a thread as long as the connection is alive. ``recv_events()`` exits immediately when the ``self.socket`` is closed. """ try: while True: try: if self.close_deadline is not None: self.socket.settimeout(self.close_deadline.timeout()) data = self.socket.recv(self.recv_bufsize) except Exception as exc: if self.debug: self.logger.debug("error while receiving data", exc_info=True) # When the closing handshake is initiated by our side, # recv() may block until send_context() closes the socket. # In that case, send_context() already set recv_exc. # Calling set_recv_exc() avoids overwriting it. with self.protocol_mutex: self.set_recv_exc(exc) break if data == b"": break # Acquire the connection lock. with self.protocol_mutex: # Feed incoming data to the protocol. self.protocol.receive_data(data) # This isn't expected to raise an exception. events = self.protocol.events_received() # Write outgoing data to the socket. try: self.send_data() except Exception as exc: if self.debug: self.logger.debug("error while sending data", exc_info=True) # Similarly to the above, avoid overriding an exception # set by send_context(), in case of a race condition # i.e. send_context() closes the socket after recv() # returns above but before send_data() calls send(). self.set_recv_exc(exc) break if self.protocol.close_expected(): # If the connection is expected to close soon, set the # close deadline based on the close timeout. if self.close_deadline is None: self.close_deadline = Deadline(self.close_timeout) # Unlock conn_mutex before processing events. Else, the # application can't send messages in response to events. # If self.send_data raised an exception, then events are lost. # Given that automatic responses write small amounts of data, # this should be uncommon, so we don't handle the edge case. try: for event in events: # This may raise EOFError if the closing handshake # times out while a message is waiting to be read. self.process_event(event) except EOFError: break # Breaking out of the while True: ... loop means that we believe # that the socket doesn't work anymore. with self.protocol_mutex: # Feed the end of the data stream to the protocol. self.protocol.receive_eof() # This isn't expected to generate events. assert not self.protocol.events_received() # There is no error handling because send_data() can only write # the end of the data stream here and it handles errors itself. self.send_data() except Exception as exc: # This branch should never run. It's a safety net in case of bugs. self.logger.error("unexpected internal error", exc_info=True) with self.protocol_mutex: self.set_recv_exc(exc) finally: # This isn't expected to raise an exception. self.close_socket() @contextlib.contextmanager def send_context( self, *, expected_state: State = OPEN, # CONNECTING during the opening handshake ) -> Iterator[None]: """ Create a context for writing to the connection from user code. On entry, :meth:`send_context` acquires the connection lock and checks that the connection is open; on exit, it writes outgoing data to the socket:: with self.send_context(): self.protocol.send_text(message.encode()) When the connection isn't open on entry, when the connection is expected to close on exit, or when an unexpected error happens, terminating the connection, :meth:`send_context` waits until the connection is closed then raises :exc:`~websockets.exceptions.ConnectionClosed`. """ # Should we wait until the connection is closed? wait_for_close = False # Should we close the socket and raise ConnectionClosed? raise_close_exc = False # What exception should we chain ConnectionClosed to? original_exc: BaseException | None = None # Acquire the protocol lock. with self.protocol_mutex: if self.protocol.state is expected_state: # Let the caller interact with the protocol. try: yield except (ProtocolError, ConcurrencyError): # The protocol state wasn't changed. Exit immediately. raise except Exception as exc: self.logger.error("unexpected internal error", exc_info=True) # This branch should never run. It's a safety net in case of # bugs. Since we don't know what happened, we will close the # connection and raise the exception to the caller. wait_for_close = False raise_close_exc = True original_exc = exc else: # Check if the connection is expected to close soon. if self.protocol.close_expected(): wait_for_close = True # If the connection is expected to close soon, set the # close deadline based on the close timeout. # Since we tested earlier that protocol.state was OPEN # (or CONNECTING) and we didn't release protocol_mutex, # it is certain that self.close_deadline is still None. assert self.close_deadline is None self.close_deadline = Deadline(self.close_timeout) # Write outgoing data to the socket. try: self.send_data() except Exception as exc: if self.debug: self.logger.debug("error while sending data", exc_info=True) # While the only expected exception here is OSError, # other exceptions would be treated identically. wait_for_close = False raise_close_exc = True original_exc = exc else: # self.protocol.state is not expected_state # Minor layering violation: we assume that the connection # will be closing soon if it isn't in the expected state. wait_for_close = True raise_close_exc = True # To avoid a deadlock, release the connection lock by exiting the # context manager before waiting for recv_events() to terminate. # If the connection is expected to close soon and the close timeout # elapses, close the socket to terminate the connection. if wait_for_close: if self.close_deadline is None: timeout = self.close_timeout else: # Thread.join() returns immediately if timeout is negative. timeout = self.close_deadline.timeout(raise_if_elapsed=False) self.recv_events_thread.join(timeout) if self.recv_events_thread.is_alive(): # There's no risk to overwrite another error because # original_exc is never set when wait_for_close is True. assert original_exc is None original_exc = TimeoutError("timed out while closing connection") # Set recv_exc before closing the socket in order to get # proper exception reporting. raise_close_exc = True with self.protocol_mutex: self.set_recv_exc(original_exc) # If an error occurred, close the socket to terminate the connection and # raise an exception. if raise_close_exc: self.close_socket() # Wait for the protocol state to be CLOSED before accessing close_exc. self.recv_events_thread.join() raise self.protocol.close_exc from original_exc def send_data(self) -> None: """ Send outgoing data. This method requires holding protocol_mutex. Raises: OSError: When a socket operations fails. """ assert self.protocol_mutex.locked() for data in self.protocol.data_to_send(): if data: if self.close_deadline is not None: self.socket.settimeout(self.close_deadline.timeout()) self.socket.sendall(data) else: try: self.socket.shutdown(socket.SHUT_WR) except OSError: # socket already closed pass def set_recv_exc(self, exc: BaseException | None) -> None: """ Set recv_exc, if not set yet. This method requires holding protocol_mutex. """ assert self.protocol_mutex.locked() if self.recv_exc is None: # pragma: no branch self.recv_exc = exc def close_socket(self) -> None: """ Shutdown and close socket. Close message assembler. Calling close_socket() guarantees that recv_events() terminates. Indeed, recv_events() may block only on socket.recv() or on recv_messages.put(). """ # shutdown() is required to interrupt recv() on Linux. try: self.socket.shutdown(socket.SHUT_RDWR) except OSError: pass # socket is already closed self.socket.close() # Calling protocol.receive_eof() is safe because it's idempotent. # This guarantees that the protocol state becomes CLOSED. self.protocol.receive_eof() assert self.protocol.state is CLOSED # Abort recv() with a ConnectionClosed exception. self.recv_messages.close()