from __future__ import annotations import asyncio import functools import logging import random import urllib.parse import warnings from types import TracebackType from typing import ( Any, AsyncIterator, Callable, Generator, List, Optional, Sequence, Tuple, Type, cast, ) from ..datastructures import Headers, HeadersLike from ..exceptions import ( InvalidHandshake, InvalidHeader, InvalidMessage, InvalidStatusCode, NegotiationError, RedirectHandshake, SecurityError, ) from ..extensions import ClientExtensionFactory, Extension from ..extensions.permessage_deflate import enable_client_permessage_deflate from ..headers import ( build_authorization_basic, build_extension, build_host, build_subprotocol, parse_extension, parse_subprotocol, validate_subprotocols, ) from ..http import USER_AGENT from ..typing import ExtensionHeader, LoggerLike, Origin, Subprotocol from ..uri import WebSocketURI, parse_uri from .handshake import build_request, check_response from .http import read_response from .protocol import WebSocketCommonProtocol __all__ = ["connect", "unix_connect", "WebSocketClientProtocol"] class WebSocketClientProtocol(WebSocketCommonProtocol): """ WebSocket client connection. :class:`WebSocketClientProtocol` provides :meth:`recv` and :meth:`send` coroutines for receiving and sending messages. It supports asynchronous iteration to receive incoming messages:: async for message in websocket: await process(message) The iterator exits normally when the connection is closed with close code 1000 (OK) or 1001 (going away). It raises a :exc:`~websockets.exceptions.ConnectionClosedError` when the connection is closed with any other code. See :func:`connect` for the documentation of ``logger``, ``origin``, ``extensions``, ``subprotocols``, and ``extra_headers``. See :class:`~websockets.legacy.protocol.WebSocketCommonProtocol` for the documentation of ``ping_interval``, ``ping_timeout``, ``close_timeout``, ``max_size``, ``max_queue``, ``read_limit``, and ``write_limit``. """ is_client = True side = "client" def __init__( self, *, logger: Optional[LoggerLike] = None, origin: Optional[Origin] = None, extensions: Optional[Sequence[ClientExtensionFactory]] = None, subprotocols: Optional[Sequence[Subprotocol]] = None, extra_headers: Optional[HeadersLike] = None, **kwargs: Any, ) -> None: if logger is None: logger = logging.getLogger("websockets.client") super().__init__(logger=logger, **kwargs) self.origin = origin self.available_extensions = extensions self.available_subprotocols = subprotocols self.extra_headers = extra_headers def write_http_request(self, path: str, headers: Headers) -> None: """ Write request line and headers to the HTTP request. """ self.path = path self.request_headers = headers if self.debug: self.logger.debug("> GET %s HTTP/1.1", path) for key, value in headers.raw_items(): self.logger.debug("> %s: %s", key, value) # Since the path and headers only contain ASCII characters, # we can keep this simple. request = f"GET {path} HTTP/1.1\r\n" request += str(headers) self.transport.write(request.encode()) async def read_http_response(self) -> Tuple[int, Headers]: """ Read status line and headers from the HTTP response. If the response contains a body, it may be read from ``self.reader`` after this coroutine returns. Raises: InvalidMessage: if the HTTP message is malformed or isn't an HTTP/1.1 GET response. """ try: status_code, reason, headers = await read_response(self.reader) # Remove this branch when dropping support for Python < 3.8 # because CancelledError no longer inherits Exception. except asyncio.CancelledError: # pragma: no cover raise except Exception as exc: raise InvalidMessage("did not receive a valid HTTP response") from exc if self.debug: self.logger.debug("< HTTP/1.1 %d %s", status_code, reason) for key, value in headers.raw_items(): self.logger.debug("< %s: %s", key, value) self.response_headers = headers return status_code, self.response_headers @staticmethod def process_extensions( headers: Headers, available_extensions: Optional[Sequence[ClientExtensionFactory]], ) -> List[Extension]: """ Handle the Sec-WebSocket-Extensions HTTP response header. Check that each extension is supported, as well as its parameters. Return the list of accepted extensions. Raise :exc:`~websockets.exceptions.InvalidHandshake` to abort the connection. :rfc:`6455` leaves the rules up to the specification of each :extension. To provide this level of flexibility, for each extension accepted by the server, we check for a match with each extension available in the client configuration. If no match is found, an exception is raised. If several variants of the same extension are accepted by the server, it may be configured several times, which won't make sense in general. Extensions must implement their own requirements. For this purpose, the list of previously accepted extensions is provided. Other requirements, for example related to mandatory extensions or the order of extensions, may be implemented by overriding this method. """ accepted_extensions: List[Extension] = [] header_values = headers.get_all("Sec-WebSocket-Extensions") if header_values: if available_extensions is None: raise InvalidHandshake("no extensions supported") parsed_header_values: List[ExtensionHeader] = sum( [parse_extension(header_value) for header_value in header_values], [] ) for name, response_params in parsed_header_values: for extension_factory in available_extensions: # Skip non-matching extensions based on their name. if extension_factory.name != name: continue # Skip non-matching extensions based on their params. try: extension = extension_factory.process_response_params( response_params, accepted_extensions ) except NegotiationError: continue # Add matching extension to the final list. accepted_extensions.append(extension) # Break out of the loop once we have a match. break # If we didn't break from the loop, no extension in our list # matched what the server sent. Fail the connection. else: raise NegotiationError( f"Unsupported extension: " f"name = {name}, params = {response_params}" ) return accepted_extensions @staticmethod def process_subprotocol( headers: Headers, available_subprotocols: Optional[Sequence[Subprotocol]] ) -> Optional[Subprotocol]: """ Handle the Sec-WebSocket-Protocol HTTP response header. Check that it contains exactly one supported subprotocol. Return the selected subprotocol. """ subprotocol: Optional[Subprotocol] = None header_values = headers.get_all("Sec-WebSocket-Protocol") if header_values: if available_subprotocols is None: raise InvalidHandshake("no subprotocols supported") parsed_header_values: Sequence[Subprotocol] = sum( [parse_subprotocol(header_value) for header_value in header_values], [] ) if len(parsed_header_values) > 1: subprotocols = ", ".join(parsed_header_values) raise InvalidHandshake(f"multiple subprotocols: {subprotocols}") subprotocol = parsed_header_values[0] if subprotocol not in available_subprotocols: raise NegotiationError(f"unsupported subprotocol: {subprotocol}") return subprotocol async def handshake( self, wsuri: WebSocketURI, origin: Optional[Origin] = None, available_extensions: Optional[Sequence[ClientExtensionFactory]] = None, available_subprotocols: Optional[Sequence[Subprotocol]] = None, extra_headers: Optional[HeadersLike] = None, ) -> None: """ Perform the client side of the opening handshake. Args: wsuri: URI of the WebSocket server. origin: value of the ``Origin`` header. available_extensions: list of supported extensions, in order in which they should be tried. available_subprotocols: list of supported subprotocols, in order of decreasing preference. extra_headers: arbitrary HTTP headers to add to the request. Raises: InvalidHandshake: if the handshake fails. """ request_headers = Headers() request_headers["Host"] = build_host(wsuri.host, wsuri.port, wsuri.secure) if wsuri.user_info: request_headers["Authorization"] = build_authorization_basic( *wsuri.user_info ) if origin is not None: request_headers["Origin"] = origin key = build_request(request_headers) if available_extensions is not None: extensions_header = build_extension( [ (extension_factory.name, extension_factory.get_request_params()) for extension_factory in available_extensions ] ) request_headers["Sec-WebSocket-Extensions"] = extensions_header if available_subprotocols is not None: protocol_header = build_subprotocol(available_subprotocols) request_headers["Sec-WebSocket-Protocol"] = protocol_header if self.extra_headers is not None: request_headers.update(self.extra_headers) request_headers.setdefault("User-Agent", USER_AGENT) self.write_http_request(wsuri.resource_name, request_headers) status_code, response_headers = await self.read_http_response() if status_code in (301, 302, 303, 307, 308): if "Location" not in response_headers: raise InvalidHeader("Location") raise RedirectHandshake(response_headers["Location"]) elif status_code != 101: raise InvalidStatusCode(status_code, response_headers) check_response(response_headers, key) self.extensions = self.process_extensions( response_headers, available_extensions ) self.subprotocol = self.process_subprotocol( response_headers, available_subprotocols ) self.connection_open() class Connect: """ Connect to the WebSocket server at ``uri``. Awaiting :func:`connect` yields a :class:`WebSocketClientProtocol` which can then be used to send and receive messages. :func:`connect` can be used as a asynchronous context manager:: async with websockets.connect(...) as websocket: ... The connection is closed automatically when exiting the context. :func:`connect` can be used as an infinite asynchronous iterator to reconnect automatically on errors:: async for websocket in websockets.connect(...): try: ... except websockets.ConnectionClosed: continue The connection is closed automatically after each iteration of the loop. If an error occurs while establishing the connection, :func:`connect` retries with exponential backoff. The backoff delay starts at three seconds and increases up to one minute. If an error occurs in the body of the loop, you can handle the exception and :func:`connect` will reconnect with the next iteration; or you can let the exception bubble up and break out of the loop. This lets you decide which errors trigger a reconnection and which errors are fatal. Args: uri: URI of the WebSocket server. create_protocol: factory for the :class:`asyncio.Protocol` managing the connection; defaults to :class:`WebSocketClientProtocol`; may be set to a wrapper or a subclass to customize connection handling. logger: logger for this connection; defaults to ``logging.getLogger("websockets.client")``; see the :doc:`logging guide <../topics/logging>` for details. compression: shortcut that enables the "permessage-deflate" extension by default; may be set to :obj:`None` to disable compression; see the :doc:`compression guide <../topics/compression>` for details. origin: value of the ``Origin`` header. This is useful when connecting to a server that validates the ``Origin`` header to defend against Cross-Site WebSocket Hijacking attacks. extensions: list of supported extensions, in order in which they should be tried. subprotocols: list of supported subprotocols, in order of decreasing preference. extra_headers: arbitrary HTTP headers to add to the request. open_timeout: timeout for opening the connection in seconds; :obj:`None` to disable the timeout See :class:`~websockets.legacy.protocol.WebSocketCommonProtocol` for the documentation of ``ping_interval``, ``ping_timeout``, ``close_timeout``, ``max_size``, ``max_queue``, ``read_limit``, and ``write_limit``. Any other keyword arguments are passed the event loop's :meth:`~asyncio.loop.create_connection` method. For example: * You can set ``ssl`` to a :class:`~ssl.SSLContext` to enforce TLS settings. When connecting to a ``wss://`` URI, if ``ssl`` isn't provided, a TLS context is created with :func:`~ssl.create_default_context`. * You can set ``host`` and ``port`` to connect to a different host and port from those found in ``uri``. This only changes the destination of the TCP connection. The host name from ``uri`` is still used in the TLS handshake for secure connections and in the ``Host`` header. Returns: WebSocketClientProtocol: WebSocket connection. Raises: InvalidURI: if ``uri`` isn't a valid WebSocket URI. InvalidHandshake: if the opening handshake fails. ~asyncio.TimeoutError: if the opening handshake times out. """ MAX_REDIRECTS_ALLOWED = 10 def __init__( self, uri: str, *, create_protocol: Optional[Callable[[Any], WebSocketClientProtocol]] = None, logger: Optional[LoggerLike] = None, compression: Optional[str] = "deflate", origin: Optional[Origin] = None, extensions: Optional[Sequence[ClientExtensionFactory]] = None, subprotocols: Optional[Sequence[Subprotocol]] = None, extra_headers: Optional[HeadersLike] = None, open_timeout: Optional[float] = 10, 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, **kwargs: Any, ) -> None: # Backwards compatibility: close_timeout used to be called timeout. timeout: Optional[float] = kwargs.pop("timeout", None) 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 # Backwards compatibility: create_protocol used to be called klass. klass: Optional[Type[WebSocketClientProtocol]] = kwargs.pop("klass", None) if klass is None: klass = WebSocketClientProtocol else: warnings.warn("rename klass to create_protocol", DeprecationWarning) # If both are specified, klass is ignored. if create_protocol is None: create_protocol = klass # Backwards compatibility: recv() used to return None on closed connections legacy_recv: bool = kwargs.pop("legacy_recv", False) # Backwards compatibility: the loop parameter used to be supported. _loop: Optional[asyncio.AbstractEventLoop] = kwargs.pop("loop", None) if _loop is None: loop = asyncio.get_event_loop() else: loop = _loop warnings.warn("remove loop argument", DeprecationWarning) wsuri = parse_uri(uri) if wsuri.secure: kwargs.setdefault("ssl", True) elif kwargs.get("ssl") is not None: raise ValueError( "connect() received a ssl argument for a ws:// URI, " "use a wss:// URI to enable TLS" ) if compression == "deflate": extensions = enable_client_permessage_deflate(extensions) elif compression is not None: raise ValueError(f"unsupported compression: {compression}") if subprotocols is not None: validate_subprotocols(subprotocols) factory = functools.partial( create_protocol, logger=logger, origin=origin, extensions=extensions, subprotocols=subprotocols, extra_headers=extra_headers, ping_interval=ping_interval, ping_timeout=ping_timeout, close_timeout=close_timeout, max_size=max_size, max_queue=max_queue, read_limit=read_limit, write_limit=write_limit, host=wsuri.host, port=wsuri.port, secure=wsuri.secure, legacy_recv=legacy_recv, loop=_loop, ) if kwargs.pop("unix", False): path: Optional[str] = kwargs.pop("path", None) create_connection = functools.partial( loop.create_unix_connection, factory, path, **kwargs ) else: host: Optional[str] port: Optional[int] if kwargs.get("sock") is None: host, port = wsuri.host, wsuri.port else: # If sock is given, host and port shouldn't be specified. host, port = None, None # If host and port are given, override values from the URI. host = kwargs.pop("host", host) port = kwargs.pop("port", port) create_connection = functools.partial( loop.create_connection, factory, host, port, **kwargs ) self.open_timeout = open_timeout if logger is None: logger = logging.getLogger("websockets.client") self.logger = logger # This is a coroutine function. self._create_connection = create_connection self._uri = uri self._wsuri = wsuri def handle_redirect(self, uri: str) -> None: # Update the state of this instance to connect to a new URI. old_uri = self._uri old_wsuri = self._wsuri new_uri = urllib.parse.urljoin(old_uri, uri) new_wsuri = parse_uri(new_uri) # Forbid TLS downgrade. if old_wsuri.secure and not new_wsuri.secure: raise SecurityError("redirect from WSS to WS") same_origin = ( old_wsuri.host == new_wsuri.host and old_wsuri.port == new_wsuri.port ) # Rewrite the host and port arguments for cross-origin redirects. # This preserves connection overrides with the host and port # arguments if the redirect points to the same host and port. if not same_origin: # Replace the host and port argument passed to the protocol factory. factory = self._create_connection.args[0] factory = functools.partial( factory.func, *factory.args, **dict(factory.keywords, host=new_wsuri.host, port=new_wsuri.port), ) # Replace the host and port argument passed to create_connection. self._create_connection = functools.partial( self._create_connection.func, *(factory, new_wsuri.host, new_wsuri.port), **self._create_connection.keywords, ) # Set the new WebSocket URI. This suffices for same-origin redirects. self._uri = new_uri self._wsuri = new_wsuri # async for ... in connect(...): BACKOFF_MIN = 1.92 BACKOFF_MAX = 60.0 BACKOFF_FACTOR = 1.618 BACKOFF_INITIAL = 5 async def __aiter__(self) -> AsyncIterator[WebSocketClientProtocol]: backoff_delay = self.BACKOFF_MIN while True: try: async with self as protocol: yield protocol # Remove this branch when dropping support for Python < 3.8 # because CancelledError no longer inherits Exception. except asyncio.CancelledError: # pragma: no cover raise except Exception: # Add a random initial delay between 0 and 5 seconds. # See 7.2.3. Recovering from Abnormal Closure in RFC 6544. if backoff_delay == self.BACKOFF_MIN: initial_delay = random.random() * self.BACKOFF_INITIAL self.logger.info( "! connect failed; reconnecting in %.1f seconds", initial_delay, exc_info=True, ) await asyncio.sleep(initial_delay) else: self.logger.info( "! connect failed again; retrying in %d seconds", int(backoff_delay), exc_info=True, ) await asyncio.sleep(int(backoff_delay)) # Increase delay with truncated exponential backoff. backoff_delay = backoff_delay * self.BACKOFF_FACTOR backoff_delay = min(backoff_delay, self.BACKOFF_MAX) continue else: # Connection succeeded - reset backoff delay backoff_delay = self.BACKOFF_MIN # async with connect(...) as ...: async def __aenter__(self) -> WebSocketClientProtocol: return await self async def __aexit__( self, exc_type: Optional[Type[BaseException]], exc_value: Optional[BaseException], traceback: Optional[TracebackType], ) -> None: await self.protocol.close() # ... = await connect(...) def __await__(self) -> Generator[Any, None, WebSocketClientProtocol]: # Create a suitable iterator by calling __await__ on a coroutine. return self.__await_impl_timeout__().__await__() async def __await_impl_timeout__(self) -> WebSocketClientProtocol: return await asyncio.wait_for(self.__await_impl__(), self.open_timeout) async def __await_impl__(self) -> WebSocketClientProtocol: for redirects in range(self.MAX_REDIRECTS_ALLOWED): transport, protocol = await self._create_connection() protocol = cast(WebSocketClientProtocol, protocol) try: await protocol.handshake( self._wsuri, origin=protocol.origin, available_extensions=protocol.available_extensions, available_subprotocols=protocol.available_subprotocols, extra_headers=protocol.extra_headers, ) except RedirectHandshake as exc: protocol.fail_connection() await protocol.wait_closed() self.handle_redirect(exc.uri) # Avoid leaking a connected socket when the handshake fails. except (Exception, asyncio.CancelledError): protocol.fail_connection() await protocol.wait_closed() raise else: self.protocol = protocol return protocol else: raise SecurityError("too many redirects") # ... = yield from connect(...) - remove when dropping Python < 3.10 __iter__ = __await__ connect = Connect def unix_connect( path: Optional[str] = None, uri: str = "ws://localhost/", **kwargs: Any, ) -> Connect: """ Similar to :func:`connect`, but for connecting to a Unix socket. This function builds upon the event loop's :meth:`~asyncio.loop.create_unix_connection` method. It is only available on Unix. It's mainly useful for debugging servers listening on Unix sockets. Args: path: file system path to the Unix socket. uri: URI of the WebSocket server; the host is used in the TLS handshake for secure connections and in the ``Host`` header. """ return connect(uri=uri, path=path, unix=True, **kwargs)