"""Implementation of the WebSocket protocol.
`WebSockets `_ allow for bidirectional
communication between the browser and server.
WebSockets are supported in the current versions of all major browsers,
although older versions that do not support WebSockets are still in use
(refer to http://caniuse.com/websockets for details).
This module implements the final version of the WebSocket protocol as
defined in `RFC 6455 `_. Certain
browser versions (notably Safari 5.x) implemented an earlier draft of
the protocol (known as "draft 76") and are not compatible with this module.
.. versionchanged:: 4.0
Removed support for the draft 76 protocol version.
"""
from __future__ import absolute_import, division, print_function
import base64
import collections
import hashlib
import os
import struct
import tornado.escape
import tornado.web
import zlib
from tornado.concurrent import Future, future_set_result_unless_cancelled
from tornado.escape import utf8, native_str, to_unicode
from tornado import gen, httpclient, httputil
from tornado.ioloop import IOLoop, PeriodicCallback
from tornado.iostream import StreamClosedError
from tornado.log import gen_log, app_log
from tornado import simple_httpclient
from tornado.tcpclient import TCPClient
from tornado.util import _websocket_mask, PY3
if PY3:
from urllib.parse import urlparse # py2
xrange = range
else:
from urlparse import urlparse # py3
class WebSocketError(Exception):
pass
class WebSocketClosedError(WebSocketError):
"""Raised by operations on a closed connection.
.. versionadded:: 3.2
"""
pass
class WebSocketHandler(tornado.web.RequestHandler):
"""Subclass this class to create a basic WebSocket handler.
Override `on_message` to handle incoming messages, and use
`write_message` to send messages to the client. You can also
override `open` and `on_close` to handle opened and closed
connections.
Custom upgrade response headers can be sent by overriding
`~tornado.web.RequestHandler.set_default_headers` or
`~tornado.web.RequestHandler.prepare`.
See http://dev.w3.org/html5/websockets/ for details on the
JavaScript interface. The protocol is specified at
http://tools.ietf.org/html/rfc6455.
Here is an example WebSocket handler that echos back all received messages
back to the client:
.. testcode::
class EchoWebSocket(tornado.websocket.WebSocketHandler):
def open(self):
print("WebSocket opened")
def on_message(self, message):
self.write_message(u"You said: " + message)
def on_close(self):
print("WebSocket closed")
.. testoutput::
:hide:
WebSockets are not standard HTTP connections. The "handshake" is
HTTP, but after the handshake, the protocol is
message-based. Consequently, most of the Tornado HTTP facilities
are not available in handlers of this type. The only communication
methods available to you are `write_message()`, `ping()`, and
`close()`. Likewise, your request handler class should implement
`open()` method rather than ``get()`` or ``post()``.
If you map the handler above to ``/websocket`` in your application, you can
invoke it in JavaScript with::
var ws = new WebSocket("ws://localhost:8888/websocket");
ws.onopen = function() {
ws.send("Hello, world");
};
ws.onmessage = function (evt) {
alert(evt.data);
};
This script pops up an alert box that says "You said: Hello, world".
Web browsers allow any site to open a websocket connection to any other,
instead of using the same-origin policy that governs other network
access from javascript. This can be surprising and is a potential
security hole, so since Tornado 4.0 `WebSocketHandler` requires
applications that wish to receive cross-origin websockets to opt in
by overriding the `~WebSocketHandler.check_origin` method (see that
method's docs for details). Failure to do so is the most likely
cause of 403 errors when making a websocket connection.
When using a secure websocket connection (``wss://``) with a self-signed
certificate, the connection from a browser may fail because it wants
to show the "accept this certificate" dialog but has nowhere to show it.
You must first visit a regular HTML page using the same certificate
to accept it before the websocket connection will succeed.
If the application setting ``websocket_ping_interval`` has a non-zero
value, a ping will be sent periodically, and the connection will be
closed if a response is not received before the ``websocket_ping_timeout``.
Messages larger than the ``websocket_max_message_size`` application setting
(default 10MiB) will not be accepted.
.. versionchanged:: 4.5
Added ``websocket_ping_interval``, ``websocket_ping_timeout``, and
``websocket_max_message_size``.
"""
def __init__(self, application, request, **kwargs):
super(WebSocketHandler, self).__init__(application, request, **kwargs)
self.ws_connection = None
self.close_code = None
self.close_reason = None
self.stream = None
self._on_close_called = False
@tornado.web.asynchronous
def get(self, *args, **kwargs):
self.open_args = args
self.open_kwargs = kwargs
# Upgrade header should be present and should be equal to WebSocket
if self.request.headers.get("Upgrade", "").lower() != 'websocket':
self.set_status(400)
log_msg = "Can \"Upgrade\" only to \"WebSocket\"."
self.finish(log_msg)
gen_log.debug(log_msg)
return
# Connection header should be upgrade.
# Some proxy servers/load balancers
# might mess with it.
headers = self.request.headers
connection = map(lambda s: s.strip().lower(),
headers.get("Connection", "").split(","))
if 'upgrade' not in connection:
self.set_status(400)
log_msg = "\"Connection\" must be \"Upgrade\"."
self.finish(log_msg)
gen_log.debug(log_msg)
return
# Handle WebSocket Origin naming convention differences
# The difference between version 8 and 13 is that in 8 the
# client sends a "Sec-Websocket-Origin" header and in 13 it's
# simply "Origin".
if "Origin" in self.request.headers:
origin = self.request.headers.get("Origin")
else:
origin = self.request.headers.get("Sec-Websocket-Origin", None)
# If there was an origin header, check to make sure it matches
# according to check_origin. When the origin is None, we assume it
# did not come from a browser and that it can be passed on.
if origin is not None and not self.check_origin(origin):
self.set_status(403)
log_msg = "Cross origin websockets not allowed"
self.finish(log_msg)
gen_log.debug(log_msg)
return
self.ws_connection = self.get_websocket_protocol()
if self.ws_connection:
self.ws_connection.accept_connection()
else:
self.set_status(426, "Upgrade Required")
self.set_header("Sec-WebSocket-Version", "7, 8, 13")
self.finish()
stream = None
@property
def ping_interval(self):
"""The interval for websocket keep-alive pings.
Set websocket_ping_interval = 0 to disable pings.
"""
return self.settings.get('websocket_ping_interval', None)
@property
def ping_timeout(self):
"""If no ping is received in this many seconds,
close the websocket connection (VPNs, etc. can fail to cleanly close ws connections).
Default is max of 3 pings or 30 seconds.
"""
return self.settings.get('websocket_ping_timeout', None)
@property
def max_message_size(self):
"""Maximum allowed message size.
If the remote peer sends a message larger than this, the connection
will be closed.
Default is 10MiB.
"""
return self.settings.get('websocket_max_message_size', None)
def write_message(self, message, binary=False):
"""Sends the given message to the client of this Web Socket.
The message may be either a string or a dict (which will be
encoded as json). If the ``binary`` argument is false, the
message will be sent as utf8; in binary mode any byte string
is allowed.
If the connection is already closed, raises `WebSocketClosedError`.
Returns a `.Future` which can be used for flow control.
.. versionchanged:: 3.2
`WebSocketClosedError` was added (previously a closed connection
would raise an `AttributeError`)
.. versionchanged:: 4.3
Returns a `.Future` which can be used for flow control.
.. versionchanged:: 5.0
Consistently raises `WebSocketClosedError`. Previously could
sometimes raise `.StreamClosedError`.
"""
if self.ws_connection is None:
raise WebSocketClosedError()
if isinstance(message, dict):
message = tornado.escape.json_encode(message)
return self.ws_connection.write_message(message, binary=binary)
def select_subprotocol(self, subprotocols):
"""Invoked when a new WebSocket requests specific subprotocols.
``subprotocols`` is a list of strings identifying the
subprotocols proposed by the client. This method may be
overridden to return one of those strings to select it, or
``None`` to not select a subprotocol. Failure to select a
subprotocol does not automatically abort the connection,
although clients may close the connection if none of their
proposed subprotocols was selected.
"""
return None
def get_compression_options(self):
"""Override to return compression options for the connection.
If this method returns None (the default), compression will
be disabled. If it returns a dict (even an empty one), it
will be enabled. The contents of the dict may be used to
control the following compression options:
``compression_level`` specifies the compression level.
``mem_level`` specifies the amount of memory used for the internal compression state.
These parameters are documented in details here:
https://docs.python.org/3.6/library/zlib.html#zlib.compressobj
.. versionadded:: 4.1
.. versionchanged:: 4.5
Added ``compression_level`` and ``mem_level``.
"""
# TODO: Add wbits option.
return None
def open(self, *args, **kwargs):
"""Invoked when a new WebSocket is opened.
The arguments to `open` are extracted from the `tornado.web.URLSpec`
regular expression, just like the arguments to
`tornado.web.RequestHandler.get`.
"""
pass
def on_message(self, message):
"""Handle incoming messages on the WebSocket
This method must be overridden.
.. versionchanged:: 4.5
``on_message`` can be a coroutine.
"""
raise NotImplementedError
def ping(self, data=b''):
"""Send ping frame to the remote end.
The data argument allows a small amount of data (up to 125
bytes) to be sent as a part of the ping message. Note that not
all websocket implementations expose this data to
applications.
Consider using the ``websocket_ping_interval`` application
setting instead of sending pings manually.
.. versionchanged:: 5.1
The data argument is now optional.
"""
data = utf8(data)
if self.ws_connection is None:
raise WebSocketClosedError()
self.ws_connection.write_ping(data)
def on_pong(self, data):
"""Invoked when the response to a ping frame is received."""
pass
def on_ping(self, data):
"""Invoked when the a ping frame is received."""
pass
def on_close(self):
"""Invoked when the WebSocket is closed.
If the connection was closed cleanly and a status code or reason
phrase was supplied, these values will be available as the attributes
``self.close_code`` and ``self.close_reason``.
.. versionchanged:: 4.0
Added ``close_code`` and ``close_reason`` attributes.
"""
pass
def close(self, code=None, reason=None):
"""Closes this Web Socket.
Once the close handshake is successful the socket will be closed.
``code`` may be a numeric status code, taken from the values
defined in `RFC 6455 section 7.4.1
`_.
``reason`` may be a textual message about why the connection is
closing. These values are made available to the client, but are
not otherwise interpreted by the websocket protocol.
.. versionchanged:: 4.0
Added the ``code`` and ``reason`` arguments.
"""
if self.ws_connection:
self.ws_connection.close(code, reason)
self.ws_connection = None
def check_origin(self, origin):
"""Override to enable support for allowing alternate origins.
The ``origin`` argument is the value of the ``Origin`` HTTP
header, the url responsible for initiating this request. This
method is not called for clients that do not send this header;
such requests are always allowed (because all browsers that
implement WebSockets support this header, and non-browser
clients do not have the same cross-site security concerns).
Should return True to accept the request or False to reject it.
By default, rejects all requests with an origin on a host other
than this one.
This is a security protection against cross site scripting attacks on
browsers, since WebSockets are allowed to bypass the usual same-origin
policies and don't use CORS headers.
.. warning::
This is an important security measure; don't disable it
without understanding the security implications. In
particular, if your authentication is cookie-based, you
must either restrict the origins allowed by
``check_origin()`` or implement your own XSRF-like
protection for websocket connections. See `these
`_
`articles
`_
for more.
To accept all cross-origin traffic (which was the default prior to
Tornado 4.0), simply override this method to always return true::
def check_origin(self, origin):
return True
To allow connections from any subdomain of your site, you might
do something like::
def check_origin(self, origin):
parsed_origin = urllib.parse.urlparse(origin)
return parsed_origin.netloc.endswith(".mydomain.com")
.. versionadded:: 4.0
"""
parsed_origin = urlparse(origin)
origin = parsed_origin.netloc
origin = origin.lower()
host = self.request.headers.get("Host")
# Check to see that origin matches host directly, including ports
return origin == host
def set_nodelay(self, value):
"""Set the no-delay flag for this stream.
By default, small messages may be delayed and/or combined to minimize
the number of packets sent. This can sometimes cause 200-500ms delays
due to the interaction between Nagle's algorithm and TCP delayed
ACKs. To reduce this delay (at the expense of possibly increasing
bandwidth usage), call ``self.set_nodelay(True)`` once the websocket
connection is established.
See `.BaseIOStream.set_nodelay` for additional details.
.. versionadded:: 3.1
"""
self.stream.set_nodelay(value)
def on_connection_close(self):
if self.ws_connection:
self.ws_connection.on_connection_close()
self.ws_connection = None
if not self._on_close_called:
self._on_close_called = True
self.on_close()
self._break_cycles()
def _break_cycles(self):
# WebSocketHandlers call finish() early, but we don't want to
# break up reference cycles (which makes it impossible to call
# self.render_string) until after we've really closed the
# connection (if it was established in the first place,
# indicated by status code 101).
if self.get_status() != 101 or self._on_close_called:
super(WebSocketHandler, self)._break_cycles()
def send_error(self, *args, **kwargs):
if self.stream is None:
super(WebSocketHandler, self).send_error(*args, **kwargs)
else:
# If we get an uncaught exception during the handshake,
# we have no choice but to abruptly close the connection.
# TODO: for uncaught exceptions after the handshake,
# we can close the connection more gracefully.
self.stream.close()
def get_websocket_protocol(self):
websocket_version = self.request.headers.get("Sec-WebSocket-Version")
if websocket_version in ("7", "8", "13"):
return WebSocketProtocol13(
self, compression_options=self.get_compression_options())
def _attach_stream(self):
self.stream = self.request.connection.detach()
self.stream.set_close_callback(self.on_connection_close)
# disable non-WS methods
for method in ["write", "redirect", "set_header", "set_cookie",
"set_status", "flush", "finish"]:
setattr(self, method, _raise_not_supported_for_websockets)
def _raise_not_supported_for_websockets(*args, **kwargs):
raise RuntimeError("Method not supported for Web Sockets")
class WebSocketProtocol(object):
"""Base class for WebSocket protocol versions.
"""
def __init__(self, handler):
self.handler = handler
self.request = handler.request
self.stream = handler.stream
self.client_terminated = False
self.server_terminated = False
def _run_callback(self, callback, *args, **kwargs):
"""Runs the given callback with exception handling.
If the callback is a coroutine, returns its Future. On error, aborts the
websocket connection and returns None.
"""
try:
result = callback(*args, **kwargs)
except Exception:
app_log.error("Uncaught exception in %s",
getattr(self.request, 'path', None), exc_info=True)
self._abort()
else:
if result is not None:
result = gen.convert_yielded(result)
self.stream.io_loop.add_future(result, lambda f: f.result())
return result
def on_connection_close(self):
self._abort()
def _abort(self):
"""Instantly aborts the WebSocket connection by closing the socket"""
self.client_terminated = True
self.server_terminated = True
self.stream.close() # forcibly tear down the connection
self.close() # let the subclass cleanup
class _PerMessageDeflateCompressor(object):
def __init__(self, persistent, max_wbits, compression_options=None):
if max_wbits is None:
max_wbits = zlib.MAX_WBITS
# There is no symbolic constant for the minimum wbits value.
if not (8 <= max_wbits <= zlib.MAX_WBITS):
raise ValueError("Invalid max_wbits value %r; allowed range 8-%d",
max_wbits, zlib.MAX_WBITS)
self._max_wbits = max_wbits
if compression_options is None or 'compression_level' not in compression_options:
self._compression_level = tornado.web.GZipContentEncoding.GZIP_LEVEL
else:
self._compression_level = compression_options['compression_level']
if compression_options is None or 'mem_level' not in compression_options:
self._mem_level = 8
else:
self._mem_level = compression_options['mem_level']
if persistent:
self._compressor = self._create_compressor()
else:
self._compressor = None
def _create_compressor(self):
return zlib.compressobj(self._compression_level,
zlib.DEFLATED, -self._max_wbits, self._mem_level)
def compress(self, data):
compressor = self._compressor or self._create_compressor()
data = (compressor.compress(data) +
compressor.flush(zlib.Z_SYNC_FLUSH))
assert data.endswith(b'\x00\x00\xff\xff')
return data[:-4]
class _PerMessageDeflateDecompressor(object):
def __init__(self, persistent, max_wbits, compression_options=None):
if max_wbits is None:
max_wbits = zlib.MAX_WBITS
if not (8 <= max_wbits <= zlib.MAX_WBITS):
raise ValueError("Invalid max_wbits value %r; allowed range 8-%d",
max_wbits, zlib.MAX_WBITS)
self._max_wbits = max_wbits
if persistent:
self._decompressor = self._create_decompressor()
else:
self._decompressor = None
def _create_decompressor(self):
return zlib.decompressobj(-self._max_wbits)
def decompress(self, data):
decompressor = self._decompressor or self._create_decompressor()
return decompressor.decompress(data + b'\x00\x00\xff\xff')
class WebSocketProtocol13(WebSocketProtocol):
"""Implementation of the WebSocket protocol from RFC 6455.
This class supports versions 7 and 8 of the protocol in addition to the
final version 13.
"""
# Bit masks for the first byte of a frame.
FIN = 0x80
RSV1 = 0x40
RSV2 = 0x20
RSV3 = 0x10
RSV_MASK = RSV1 | RSV2 | RSV3
OPCODE_MASK = 0x0f
def __init__(self, handler, mask_outgoing=False,
compression_options=None):
WebSocketProtocol.__init__(self, handler)
self.mask_outgoing = mask_outgoing
self._final_frame = False
self._frame_opcode = None
self._masked_frame = None
self._frame_mask = None
self._frame_length = None
self._fragmented_message_buffer = None
self._fragmented_message_opcode = None
self._waiting = None
self._compression_options = compression_options
self._decompressor = None
self._compressor = None
self._frame_compressed = None
# The total uncompressed size of all messages received or sent.
# Unicode messages are encoded to utf8.
# Only for testing; subject to change.
self._message_bytes_in = 0
self._message_bytes_out = 0
# The total size of all packets received or sent. Includes
# the effect of compression, frame overhead, and control frames.
self._wire_bytes_in = 0
self._wire_bytes_out = 0
self.ping_callback = None
self.last_ping = 0
self.last_pong = 0
def accept_connection(self):
try:
self._handle_websocket_headers()
except ValueError:
self.handler.set_status(400)
log_msg = "Missing/Invalid WebSocket headers"
self.handler.finish(log_msg)
gen_log.debug(log_msg)
return
try:
self._accept_connection()
except ValueError:
gen_log.debug("Malformed WebSocket request received",
exc_info=True)
self._abort()
return
def _handle_websocket_headers(self):
"""Verifies all invariant- and required headers
If a header is missing or have an incorrect value ValueError will be
raised
"""
fields = ("Host", "Sec-Websocket-Key", "Sec-Websocket-Version")
if not all(map(lambda f: self.request.headers.get(f), fields)):
raise ValueError("Missing/Invalid WebSocket headers")
@staticmethod
def compute_accept_value(key):
"""Computes the value for the Sec-WebSocket-Accept header,
given the value for Sec-WebSocket-Key.
"""
sha1 = hashlib.sha1()
sha1.update(utf8(key))
sha1.update(b"258EAFA5-E914-47DA-95CA-C5AB0DC85B11") # Magic value
return native_str(base64.b64encode(sha1.digest()))
def _challenge_response(self):
return WebSocketProtocol13.compute_accept_value(
self.request.headers.get("Sec-Websocket-Key"))
def _accept_connection(self):
subprotocols = [s.strip() for s in self.request.headers.get_list("Sec-WebSocket-Protocol")]
if subprotocols:
selected = self.handler.select_subprotocol(subprotocols)
if selected:
assert selected in subprotocols
self.handler.set_header("Sec-WebSocket-Protocol", selected)
extensions = self._parse_extensions_header(self.request.headers)
for ext in extensions:
if (ext[0] == 'permessage-deflate' and
self._compression_options is not None):
# TODO: negotiate parameters if compression_options
# specifies limits.
self._create_compressors('server', ext[1], self._compression_options)
if ('client_max_window_bits' in ext[1] and
ext[1]['client_max_window_bits'] is None):
# Don't echo an offered client_max_window_bits
# parameter with no value.
del ext[1]['client_max_window_bits']
self.handler.set_header("Sec-WebSocket-Extensions",
httputil._encode_header(
'permessage-deflate', ext[1]))
break
self.handler.clear_header("Content-Type")
self.handler.set_status(101)
self.handler.set_header("Upgrade", "websocket")
self.handler.set_header("Connection", "Upgrade")
self.handler.set_header("Sec-WebSocket-Accept", self._challenge_response())
self.handler.finish()
self.handler._attach_stream()
self.stream = self.handler.stream
self.start_pinging()
self._run_callback(self.handler.open, *self.handler.open_args,
**self.handler.open_kwargs)
self._receive_frame()
def _parse_extensions_header(self, headers):
extensions = headers.get("Sec-WebSocket-Extensions", '')
if extensions:
return [httputil._parse_header(e.strip())
for e in extensions.split(',')]
return []
def _process_server_headers(self, key, headers):
"""Process the headers sent by the server to this client connection.
'key' is the websocket handshake challenge/response key.
"""
assert headers['Upgrade'].lower() == 'websocket'
assert headers['Connection'].lower() == 'upgrade'
accept = self.compute_accept_value(key)
assert headers['Sec-Websocket-Accept'] == accept
extensions = self._parse_extensions_header(headers)
for ext in extensions:
if (ext[0] == 'permessage-deflate' and
self._compression_options is not None):
self._create_compressors('client', ext[1])
else:
raise ValueError("unsupported extension %r", ext)
def _get_compressor_options(self, side, agreed_parameters, compression_options=None):
"""Converts a websocket agreed_parameters set to keyword arguments
for our compressor objects.
"""
options = dict(
persistent=(side + '_no_context_takeover') not in agreed_parameters)
wbits_header = agreed_parameters.get(side + '_max_window_bits', None)
if wbits_header is None:
options['max_wbits'] = zlib.MAX_WBITS
else:
options['max_wbits'] = int(wbits_header)
options['compression_options'] = compression_options
return options
def _create_compressors(self, side, agreed_parameters, compression_options=None):
# TODO: handle invalid parameters gracefully
allowed_keys = set(['server_no_context_takeover',
'client_no_context_takeover',
'server_max_window_bits',
'client_max_window_bits'])
for key in agreed_parameters:
if key not in allowed_keys:
raise ValueError("unsupported compression parameter %r" % key)
other_side = 'client' if (side == 'server') else 'server'
self._compressor = _PerMessageDeflateCompressor(
**self._get_compressor_options(side, agreed_parameters, compression_options))
self._decompressor = _PerMessageDeflateDecompressor(
**self._get_compressor_options(other_side, agreed_parameters, compression_options))
def _write_frame(self, fin, opcode, data, flags=0):
data_len = len(data)
if opcode & 0x8:
# All control frames MUST have a payload length of 125
# bytes or less and MUST NOT be fragmented.
if not fin:
raise ValueError("control frames may not be fragmented")
if data_len > 125:
raise ValueError("control frame payloads may not exceed 125 bytes")
if fin:
finbit = self.FIN
else:
finbit = 0
frame = struct.pack("B", finbit | opcode | flags)
if self.mask_outgoing:
mask_bit = 0x80
else:
mask_bit = 0
if data_len < 126:
frame += struct.pack("B", data_len | mask_bit)
elif data_len <= 0xFFFF:
frame += struct.pack("!BH", 126 | mask_bit, data_len)
else:
frame += struct.pack("!BQ", 127 | mask_bit, data_len)
if self.mask_outgoing:
mask = os.urandom(4)
data = mask + _websocket_mask(mask, data)
frame += data
self._wire_bytes_out += len(frame)
return self.stream.write(frame)
def write_message(self, message, binary=False):
"""Sends the given message to the client of this Web Socket."""
if binary:
opcode = 0x2
else:
opcode = 0x1
message = tornado.escape.utf8(message)
assert isinstance(message, bytes)
self._message_bytes_out += len(message)
flags = 0
if self._compressor:
message = self._compressor.compress(message)
flags |= self.RSV1
# For historical reasons, write methods in Tornado operate in a semi-synchronous
# mode in which awaiting the Future they return is optional (But errors can
# still be raised). This requires us to go through an awkward dance here
# to transform the errors that may be returned while presenting the same
# semi-synchronous interface.
try:
fut = self._write_frame(True, opcode, message, flags=flags)
except StreamClosedError:
raise WebSocketClosedError()
@gen.coroutine
def wrapper():
try:
yield fut
except StreamClosedError:
raise WebSocketClosedError()
return wrapper()
def write_ping(self, data):
"""Send ping frame."""
assert isinstance(data, bytes)
self._write_frame(True, 0x9, data)
def _receive_frame(self):
try:
self.stream.read_bytes(2, self._on_frame_start)
except StreamClosedError:
self._abort()
def _on_frame_start(self, data):
self._wire_bytes_in += len(data)
header, payloadlen = struct.unpack("BB", data)
self._final_frame = header & self.FIN
reserved_bits = header & self.RSV_MASK
self._frame_opcode = header & self.OPCODE_MASK
self._frame_opcode_is_control = self._frame_opcode & 0x8
if self._decompressor is not None and self._frame_opcode != 0:
self._frame_compressed = bool(reserved_bits & self.RSV1)
reserved_bits &= ~self.RSV1
if reserved_bits:
# client is using as-yet-undefined extensions; abort
self._abort()
return
self._masked_frame = bool(payloadlen & 0x80)
payloadlen = payloadlen & 0x7f
if self._frame_opcode_is_control and payloadlen >= 126:
# control frames must have payload < 126
self._abort()
return
try:
if payloadlen < 126:
self._frame_length = payloadlen
if self._masked_frame:
self.stream.read_bytes(4, self._on_masking_key)
else:
self._read_frame_data(False)
elif payloadlen == 126:
self.stream.read_bytes(2, self._on_frame_length_16)
elif payloadlen == 127:
self.stream.read_bytes(8, self._on_frame_length_64)
except StreamClosedError:
self._abort()
def _read_frame_data(self, masked):
new_len = self._frame_length
if self._fragmented_message_buffer is not None:
new_len += len(self._fragmented_message_buffer)
if new_len > (self.handler.max_message_size or 10 * 1024 * 1024):
self.close(1009, "message too big")
return
self.stream.read_bytes(
self._frame_length,
self._on_masked_frame_data if masked else self._on_frame_data)
def _on_frame_length_16(self, data):
self._wire_bytes_in += len(data)
self._frame_length = struct.unpack("!H", data)[0]
try:
if self._masked_frame:
self.stream.read_bytes(4, self._on_masking_key)
else:
self._read_frame_data(False)
except StreamClosedError:
self._abort()
def _on_frame_length_64(self, data):
self._wire_bytes_in += len(data)
self._frame_length = struct.unpack("!Q", data)[0]
try:
if self._masked_frame:
self.stream.read_bytes(4, self._on_masking_key)
else:
self._read_frame_data(False)
except StreamClosedError:
self._abort()
def _on_masking_key(self, data):
self._wire_bytes_in += len(data)
self._frame_mask = data
try:
self._read_frame_data(True)
except StreamClosedError:
self._abort()
def _on_masked_frame_data(self, data):
# Don't touch _wire_bytes_in; we'll do it in _on_frame_data.
self._on_frame_data(_websocket_mask(self._frame_mask, data))
def _on_frame_data(self, data):
handled_future = None
self._wire_bytes_in += len(data)
if self._frame_opcode_is_control:
# control frames may be interleaved with a series of fragmented
# data frames, so control frames must not interact with
# self._fragmented_*
if not self._final_frame:
# control frames must not be fragmented
self._abort()
return
opcode = self._frame_opcode
elif self._frame_opcode == 0: # continuation frame
if self._fragmented_message_buffer is None:
# nothing to continue
self._abort()
return
self._fragmented_message_buffer += data
if self._final_frame:
opcode = self._fragmented_message_opcode
data = self._fragmented_message_buffer
self._fragmented_message_buffer = None
else: # start of new data message
if self._fragmented_message_buffer is not None:
# can't start new message until the old one is finished
self._abort()
return
if self._final_frame:
opcode = self._frame_opcode
else:
self._fragmented_message_opcode = self._frame_opcode
self._fragmented_message_buffer = data
if self._final_frame:
handled_future = self._handle_message(opcode, data)
if not self.client_terminated:
if handled_future:
# on_message is a coroutine, process more frames once it's done.
handled_future.add_done_callback(
lambda future: self._receive_frame())
else:
self._receive_frame()
def _handle_message(self, opcode, data):
"""Execute on_message, returning its Future if it is a coroutine."""
if self.client_terminated:
return
if self._frame_compressed:
data = self._decompressor.decompress(data)
if opcode == 0x1:
# UTF-8 data
self._message_bytes_in += len(data)
try:
decoded = data.decode("utf-8")
except UnicodeDecodeError:
self._abort()
return
return self._run_callback(self.handler.on_message, decoded)
elif opcode == 0x2:
# Binary data
self._message_bytes_in += len(data)
return self._run_callback(self.handler.on_message, data)
elif opcode == 0x8:
# Close
self.client_terminated = True
if len(data) >= 2:
self.handler.close_code = struct.unpack('>H', data[:2])[0]
if len(data) > 2:
self.handler.close_reason = to_unicode(data[2:])
# Echo the received close code, if any (RFC 6455 section 5.5.1).
self.close(self.handler.close_code)
elif opcode == 0x9:
# Ping
try:
self._write_frame(True, 0xA, data)
except StreamClosedError:
self._abort()
self._run_callback(self.handler.on_ping, data)
elif opcode == 0xA:
# Pong
self.last_pong = IOLoop.current().time()
return self._run_callback(self.handler.on_pong, data)
else:
self._abort()
def close(self, code=None, reason=None):
"""Closes the WebSocket connection."""
if not self.server_terminated:
if not self.stream.closed():
if code is None and reason is not None:
code = 1000 # "normal closure" status code
if code is None:
close_data = b''
else:
close_data = struct.pack('>H', code)
if reason is not None:
close_data += utf8(reason)
try:
self._write_frame(True, 0x8, close_data)
except StreamClosedError:
self._abort()
self.server_terminated = True
if self.client_terminated:
if self._waiting is not None:
self.stream.io_loop.remove_timeout(self._waiting)
self._waiting = None
self.stream.close()
elif self._waiting is None:
# Give the client a few seconds to complete a clean shutdown,
# otherwise just close the connection.
self._waiting = self.stream.io_loop.add_timeout(
self.stream.io_loop.time() + 5, self._abort)
@property
def ping_interval(self):
interval = self.handler.ping_interval
if interval is not None:
return interval
return 0
@property
def ping_timeout(self):
timeout = self.handler.ping_timeout
if timeout is not None:
return timeout
return max(3 * self.ping_interval, 30)
def start_pinging(self):
"""Start sending periodic pings to keep the connection alive"""
if self.ping_interval > 0:
self.last_ping = self.last_pong = IOLoop.current().time()
self.ping_callback = PeriodicCallback(
self.periodic_ping, self.ping_interval * 1000)
self.ping_callback.start()
def periodic_ping(self):
"""Send a ping to keep the websocket alive
Called periodically if the websocket_ping_interval is set and non-zero.
"""
if self.stream.closed() and self.ping_callback is not None:
self.ping_callback.stop()
return
# Check for timeout on pong. Make sure that we really have
# sent a recent ping in case the machine with both server and
# client has been suspended since the last ping.
now = IOLoop.current().time()
since_last_pong = now - self.last_pong
since_last_ping = now - self.last_ping
if (since_last_ping < 2 * self.ping_interval and
since_last_pong > self.ping_timeout):
self.close()
return
self.write_ping(b'')
self.last_ping = now
class WebSocketClientConnection(simple_httpclient._HTTPConnection):
"""WebSocket client connection.
This class should not be instantiated directly; use the
`websocket_connect` function instead.
"""
def __init__(self, request, on_message_callback=None,
compression_options=None, ping_interval=None, ping_timeout=None,
max_message_size=None):
self.compression_options = compression_options
self.connect_future = Future()
self.protocol = None
self.read_future = None
self.read_queue = collections.deque()
self.key = base64.b64encode(os.urandom(16))
self._on_message_callback = on_message_callback
self.close_code = self.close_reason = None
self.ping_interval = ping_interval
self.ping_timeout = ping_timeout
self.max_message_size = max_message_size
scheme, sep, rest = request.url.partition(':')
scheme = {'ws': 'http', 'wss': 'https'}[scheme]
request.url = scheme + sep + rest
request.headers.update({
'Upgrade': 'websocket',
'Connection': 'Upgrade',
'Sec-WebSocket-Key': self.key,
'Sec-WebSocket-Version': '13',
})
if self.compression_options is not None:
# Always offer to let the server set our max_wbits (and even though
# we don't offer it, we will accept a client_no_context_takeover
# from the server).
# TODO: set server parameters for deflate extension
# if requested in self.compression_options.
request.headers['Sec-WebSocket-Extensions'] = (
'permessage-deflate; client_max_window_bits')
self.tcp_client = TCPClient()
super(WebSocketClientConnection, self).__init__(
None, request, lambda: None, self._on_http_response,
104857600, self.tcp_client, 65536, 104857600)
def close(self, code=None, reason=None):
"""Closes the websocket connection.
``code`` and ``reason`` are documented under
`WebSocketHandler.close`.
.. versionadded:: 3.2
.. versionchanged:: 4.0
Added the ``code`` and ``reason`` arguments.
"""
if self.protocol is not None:
self.protocol.close(code, reason)
self.protocol = None
def on_connection_close(self):
if not self.connect_future.done():
self.connect_future.set_exception(StreamClosedError())
self.on_message(None)
self.tcp_client.close()
super(WebSocketClientConnection, self).on_connection_close()
def _on_http_response(self, response):
if not self.connect_future.done():
if response.error:
self.connect_future.set_exception(response.error)
else:
self.connect_future.set_exception(WebSocketError(
"Non-websocket response"))
def headers_received(self, start_line, headers):
if start_line.code != 101:
return super(WebSocketClientConnection, self).headers_received(
start_line, headers)
self.headers = headers
self.protocol = self.get_websocket_protocol()
self.protocol._process_server_headers(self.key, self.headers)
self.protocol.start_pinging()
self.protocol._receive_frame()
if self._timeout is not None:
self.io_loop.remove_timeout(self._timeout)
self._timeout = None
self.stream = self.connection.detach()
self.stream.set_close_callback(self.on_connection_close)
# Once we've taken over the connection, clear the final callback
# we set on the http request. This deactivates the error handling
# in simple_httpclient that would otherwise interfere with our
# ability to see exceptions.
self.final_callback = None
future_set_result_unless_cancelled(self.connect_future, self)
def write_message(self, message, binary=False):
"""Sends a message to the WebSocket server.
If the stream is closed, raises `WebSocketClosedError`.
Returns a `.Future` which can be used for flow control.
.. versionchanged:: 5.0
Exception raised on a closed stream changed from `.StreamClosedError`
to `WebSocketClosedError`.
"""
return self.protocol.write_message(message, binary=binary)
def read_message(self, callback=None):
"""Reads a message from the WebSocket server.
If on_message_callback was specified at WebSocket
initialization, this function will never return messages
Returns a future whose result is the message, or None
if the connection is closed. If a callback argument
is given it will be called with the future when it is
ready.
"""
assert self.read_future is None
future = Future()
if self.read_queue:
future_set_result_unless_cancelled(future, self.read_queue.popleft())
else:
self.read_future = future
if callback is not None:
self.io_loop.add_future(future, callback)
return future
def on_message(self, message):
if self._on_message_callback:
self._on_message_callback(message)
elif self.read_future is not None:
future_set_result_unless_cancelled(self.read_future, message)
self.read_future = None
else:
self.read_queue.append(message)
def ping(self, data=b''):
"""Send ping frame to the remote end.
The data argument allows a small amount of data (up to 125
bytes) to be sent as a part of the ping message. Note that not
all websocket implementations expose this data to
applications.
Consider using the ``ping_interval`` argument to
`websocket_connect` instead of sending pings manually.
.. versionadded:: 5.1
"""
data = utf8(data)
if self.protocol is None:
raise WebSocketClosedError()
self.protocol.write_ping(data)
def on_pong(self, data):
pass
def on_ping(self, data):
pass
def get_websocket_protocol(self):
return WebSocketProtocol13(self, mask_outgoing=True,
compression_options=self.compression_options)
def websocket_connect(url, callback=None, connect_timeout=None,
on_message_callback=None, compression_options=None,
ping_interval=None, ping_timeout=None,
max_message_size=None):
"""Client-side websocket support.
Takes a url and returns a Future whose result is a
`WebSocketClientConnection`.
``compression_options`` is interpreted in the same way as the
return value of `.WebSocketHandler.get_compression_options`.
The connection supports two styles of operation. In the coroutine
style, the application typically calls
`~.WebSocketClientConnection.read_message` in a loop::
conn = yield websocket_connect(url)
while True:
msg = yield conn.read_message()
if msg is None: break
# Do something with msg
In the callback style, pass an ``on_message_callback`` to
``websocket_connect``. In both styles, a message of ``None``
indicates that the connection has been closed.
.. versionchanged:: 3.2
Also accepts ``HTTPRequest`` objects in place of urls.
.. versionchanged:: 4.1
Added ``compression_options`` and ``on_message_callback``.
.. versionchanged:: 4.5
Added the ``ping_interval``, ``ping_timeout``, and ``max_message_size``
arguments, which have the same meaning as in `WebSocketHandler`.
.. versionchanged:: 5.0
The ``io_loop`` argument (deprecated since version 4.1) has been removed.
"""
if isinstance(url, httpclient.HTTPRequest):
assert connect_timeout is None
request = url
# Copy and convert the headers dict/object (see comments in
# AsyncHTTPClient.fetch)
request.headers = httputil.HTTPHeaders(request.headers)
else:
request = httpclient.HTTPRequest(url, connect_timeout=connect_timeout)
request = httpclient._RequestProxy(
request, httpclient.HTTPRequest._DEFAULTS)
conn = WebSocketClientConnection(request,
on_message_callback=on_message_callback,
compression_options=compression_options,
ping_interval=ping_interval,
ping_timeout=ping_timeout,
max_message_size=max_message_size)
if callback is not None:
IOLoop.current().add_future(conn.connect_future, callback)
return conn.connect_future