forked from tornadoweb/tornado
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websocket.py
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websocket.py
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"""Server-side implementation of the WebSocket protocol.
`WebSockets <http://dev.w3.org/html5/websockets/>`_ allow for bidirectional
communication between the browser and server.
.. warning::
The WebSocket protocol is still in development. This module
currently implements the "hixie-76", "hybi-10", and "hybi-17"
versions of the protocol. See this `browser compatibility table
<http://en.wikipedia.org/wiki/WebSockets#Browser_support>`_ on
Wikipedia.
"""
# Author: Jacob Kristhammar, 2010
import functools
import hashlib
import logging
import struct
import time
import base64
import tornado.escape
import tornado.web
from tornado.util import bytes_type, b
class WebSocketHandler(tornado.web.RequestHandler):
"""Subclass this class to create a basic WebSocket handler.
Override on_message to handle incoming messages. You can also override
open and on_close to handle opened and closed connections.
See http://dev.w3.org/html5/websockets/ for details on the
JavaScript interface. This implement the protocol as specified at
http://tools.ietf.org/html/draft-ietf-hybi-thewebsocketprotocol-17
The older protocol versions specified at
http://tools.ietf.org/html/draft-ietf-hybi-thewebsocketprotocol-10
and
http://tools.ietf.org/html/draft-hixie-thewebsocketprotocol-76.
are also supported.
Here is an example Web Socket handler that echos back all received messages
back to the client::
class EchoWebSocket(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"
Web Sockets 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()
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".
"""
def __init__(self, application, request, **kwargs):
tornado.web.RequestHandler.__init__(self, application, request,
**kwargs)
self.stream = request.connection.stream
self.ws_connection = None
def _execute(self, transforms, *args, **kwargs):
self.open_args = args
self.open_kwargs = kwargs
# 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 self.request.headers.get("Sec-WebSocket-Version") in ("7", "8", "13"):
self.ws_connection = WebSocketProtocol8(self)
self.ws_connection.accept_connection()
elif self.request.headers.get("Sec-WebSocket-Version"):
self.stream.write(tornado.escape.utf8(
"HTTP/1.1 426 Upgrade Required\r\n"
"Sec-WebSocket-Version: 8\r\n\r\n"))
self.stream.close()
else:
self.ws_connection = WebSocketProtocol76(self)
self.ws_connection.accept_connection()
def write_message(self, message):
"""Sends the given message to the client of this Web Socket."""
self.ws_connection.write_message(message)
def open(self, *args, **kwargs):
"""Invoked when a new WebSocket is opened."""
pass
def on_message(self, message):
"""Handle incoming messages on the WebSocket
This method must be overloaded
"""
raise NotImplementedError
def on_close(self):
"""Invoked when the WebSocket is closed."""
pass
def close(self):
"""Closes this Web Socket.
Once the close handshake is successful the socket will be closed.
"""
self.ws_connection.close()
def async_callback(self, callback, *args, **kwargs):
"""Wrap callbacks with this if they are used on asynchronous requests.
Catches exceptions properly and closes this WebSocket if an exception
is uncaught.
"""
return self.ws_connection.async_callback(callback, *args, **kwargs)
def _not_supported(self, *args, **kwargs):
raise Exception("Method not supported for Web Sockets")
def on_connection_close(self):
if self.ws_connection:
self.ws_connection.client_terminated = True
self.on_close()
def _set_client_terminated(self, value):
self.ws_connection.client_terminated = value
client_terminated = property(lambda self: self.ws_connection.client_terminated,
_set_client_terminated)
for method in ["write", "redirect", "set_header", "send_error", "set_cookie",
"set_status", "flush", "finish"]:
setattr(WebSocketHandler, method, WebSocketHandler._not_supported)
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
def async_callback(self, callback, *args, **kwargs):
"""Wrap callbacks with this if they are used on asynchronous requests.
Catches exceptions properly and closes this WebSocket if an exception
is uncaught.
"""
if args or kwargs:
callback = functools.partial(callback, *args, **kwargs)
def wrapper(*args, **kwargs):
try:
return callback(*args, **kwargs)
except Exception:
logging.error("Uncaught exception in %s",
self.request.path, exc_info=True)
self._abort()
return wrapper
def _abort(self):
"""Instantly aborts the WebSocket connection by closing the socket"""
self.client_terminated = True
self.stream.close()
class WebSocketProtocol76(WebSocketProtocol):
"""Implementation of the WebSockets protocol, version hixie-76.
This class provides basic functionality to process WebSockets requests as
specified in
http://tools.ietf.org/html/draft-hixie-thewebsocketprotocol-76
"""
def __init__(self, handler):
WebSocketProtocol.__init__(self, handler)
self.challenge = None
self._waiting = None
def accept_connection(self):
try:
self._handle_websocket_headers()
except ValueError:
logging.debug("Malformed WebSocket request received")
self._abort()
return
scheme = "wss" if self.request.protocol == "https" else "ws"
# Write the initial headers before attempting to read the challenge.
# This is necessary when using proxies (such as HAProxy), which
# need to see the Upgrade headers before passing through the
# non-HTTP traffic that follows.
self.stream.write(tornado.escape.utf8(
"HTTP/1.1 101 WebSocket Protocol Handshake\r\n"
"Upgrade: WebSocket\r\n"
"Connection: Upgrade\r\n"
"Server: TornadoServer/%(version)s\r\n"
"Sec-WebSocket-Origin: %(origin)s\r\n"
"Sec-WebSocket-Location: %(scheme)s://%(host)s%(uri)s\r\n\r\n" % (dict(
version=tornado.version,
origin=self.request.headers["Origin"],
scheme=scheme,
host=self.request.host,
uri=self.request.uri))))
self.stream.read_bytes(8, self._handle_challenge)
def challenge_response(self, challenge):
"""Generates the challenge response that's needed in the handshake
The challenge parameter should be the raw bytes as sent from the
client.
"""
key_1 = self.request.headers.get("Sec-Websocket-Key1")
key_2 = self.request.headers.get("Sec-Websocket-Key2")
try:
part_1 = self._calculate_part(key_1)
part_2 = self._calculate_part(key_2)
except ValueError:
raise ValueError("Invalid Keys/Challenge")
return self._generate_challenge_response(part_1, part_2, challenge)
def _handle_challenge(self, challenge):
try:
challenge_response = self.challenge_response(challenge)
except ValueError:
logging.debug("Malformed key data in WebSocket request")
self._abort()
return
self._write_response(challenge_response)
def _write_response(self, challenge):
self.stream.write(challenge)
self.async_callback(self.handler.open)(*self.handler.open_args, **self.handler.open_kwargs)
self._receive_message()
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
"""
headers = self.request.headers
fields = ("Origin", "Host", "Sec-Websocket-Key1",
"Sec-Websocket-Key2")
if headers.get("Upgrade", '').lower() != "websocket" or \
headers.get("Connection", '').lower() != "upgrade" or \
not all(map(lambda f: self.request.headers.get(f), fields)):
raise ValueError("Missing/Invalid WebSocket headers")
def _calculate_part(self, key):
"""Processes the key headers and calculates their key value.
Raises ValueError when feed invalid key."""
number = int(''.join(c for c in key if c.isdigit()))
spaces = len([c for c in key if c.isspace()])
try:
key_number = number // spaces
except (ValueError, ZeroDivisionError):
raise ValueError
return struct.pack(">I", key_number)
def _generate_challenge_response(self, part_1, part_2, part_3):
m = hashlib.md5()
m.update(part_1)
m.update(part_2)
m.update(part_3)
return m.digest()
def _receive_message(self):
self.stream.read_bytes(1, self._on_frame_type)
def _on_frame_type(self, byte):
frame_type = ord(byte)
if frame_type == 0x00:
self.stream.read_until(b("\xff"), self._on_end_delimiter)
elif frame_type == 0xff:
self.stream.read_bytes(1, self._on_length_indicator)
else:
self._abort()
def _on_end_delimiter(self, frame):
if not self.client_terminated:
self.async_callback(self.handler.on_message)(
frame[:-1].decode("utf-8", "replace"))
if not self.client_terminated:
self._receive_message()
def _on_length_indicator(self, byte):
if ord(byte) != 0x00:
self._abort()
return
self.client_terminated = True
self.close()
def write_message(self, message):
"""Sends the given message to the client of this Web Socket."""
if isinstance(message, dict):
message = tornado.escape.json_encode(message)
if isinstance(message, unicode):
message = message.encode("utf-8")
assert isinstance(message, bytes_type)
self.stream.write(b("\x00") + message + b("\xff"))
def close(self):
"""Closes the WebSocket connection."""
if self.client_terminated and self._waiting:
tornado.ioloop.IOLoop.instance().remove_timeout(self._waiting)
self.stream.close()
else:
self.stream.write("\xff\x00")
self._waiting = tornado.ioloop.IOLoop.instance().add_timeout(
time.time() + 5, self._abort)
class WebSocketProtocol8(WebSocketProtocol):
"""Implementation of the WebSocket protocol, version 8 (draft version 10).
Compare
http://tools.ietf.org/html/draft-ietf-hybi-thewebsocketprotocol-10
"""
def __init__(self, handler):
WebSocketProtocol.__init__(self, handler)
self._final_frame = False
self._frame_opcode = None
self._frame_mask = None
self._frame_length = None
self._fragmented_message_buffer = None
self._fragmented_message_opcode = None
self._started_closing_handshake = False
def accept_connection(self):
try:
self._handle_websocket_headers()
self._accept_connection()
except ValueError:
logging.debug("Malformed WebSocket request received")
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
"""
headers = self.request.headers
fields = ("Host", "Sec-Websocket-Key", "Sec-Websocket-Version")
connection = map(lambda s: s.strip().lower(), headers.get("Connection", '').split(","))
if (self.request.method != "GET" or
headers.get("Upgrade", '').lower() != "websocket" or
"upgrade" not in connection or
not all(map(lambda f: self.request.headers.get(f), fields))):
raise ValueError("Missing/Invalid WebSocket headers")
def _challenge_response(self):
sha1 = hashlib.sha1()
sha1.update(tornado.escape.utf8(
self.request.headers.get("Sec-Websocket-Key")))
sha1.update(b("258EAFA5-E914-47DA-95CA-C5AB0DC85B11")) # Magic value
return tornado.escape.native_str(base64.b64encode(sha1.digest()))
def _accept_connection(self):
self.stream.write(tornado.escape.utf8(
"HTTP/1.1 101 Switching Protocols\r\n"
"Upgrade: websocket\r\n"
"Connection: Upgrade\r\n"
"Sec-WebSocket-Accept: %s\r\n\r\n" % self._challenge_response()))
self.async_callback(self.handler.open)(*self.handler.open_args, **self.handler.open_kwargs)
self._receive_frame()
def _write_frame(self, fin, opcode, data):
if fin:
finbit = 0x80
else:
finbit = 0
frame = struct.pack("B", finbit | opcode)
l = len(data)
if l < 126:
frame += struct.pack("B", l)
elif l <= 0xFFFF:
frame += struct.pack("!BH", 126, l)
else:
frame += struct.pack("!BQ", 127, l)
frame += data
self.stream.write(frame)
def write_message(self, message, binary=False):
"""Sends the given message to the client of this Web Socket."""
if isinstance(message, dict):
message = tornado.escape.json_encode(message)
if isinstance(message, unicode):
message = message.encode("utf-8")
assert isinstance(message, bytes_type)
if not binary:
opcode = 0x1
else:
opcode = 0x2
self._write_frame(True, opcode, message)
def _receive_frame(self):
self.stream.read_bytes(2, self._on_frame_start)
def _on_frame_start(self, data):
header, payloadlen = struct.unpack("BB", data)
self._final_frame = header & 0x80
self._frame_opcode = header & 0xf
if not (payloadlen & 0x80):
# Unmasked frame -> abort connection
self._abort()
payloadlen = payloadlen & 0x7f
if payloadlen < 126:
self._frame_length = payloadlen
self.stream.read_bytes(4, self._on_masking_key)
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)
def _on_frame_length_16(self, data):
self._frame_length = struct.unpack("!H", data)[0];
self.stream.read_bytes(4, self._on_masking_key);
def _on_frame_length_64(self, data):
self._frame_length = struct.unpack("!Q", data)[0];
self.stream.read_bytes(4, self._on_masking_key);
def _on_masking_key(self, data):
self._frame_mask = bytearray(data)
self.stream.read_bytes(self._frame_length, self._on_frame_data)
def _on_frame_data(self, data):
unmasked = bytearray(data)
for i in xrange(len(data)):
unmasked[i] = unmasked[i] ^ self._frame_mask[i % 4]
if not self._final_frame:
if self._fragmented_message_buffer:
self._fragmented_message_buffer += unmasked
else:
self._fragmented_message_opcode = self._frame_opcode
self._fragmented_message_buffer = unmasked
else:
if self._frame_opcode == 0:
unmasked = self._fragmented_message_buffer + unmasked
opcode = self._fragmented_message_opcode
self._fragmented_message_buffer = None
else:
opcode = self._frame_opcode
self._handle_message(opcode, bytes_type(unmasked))
if not self.client_terminated:
self._receive_frame()
def _handle_message(self, opcode, data):
if self.client_terminated: return
if opcode == 0x1:
# UTF-8 data
self.async_callback(self.handler.on_message)(data.decode("utf-8", "replace"))
elif opcode == 0x2:
# Binary data
self.async_callback(self.handler.on_message)(data)
elif opcode == 0x8:
# Close
self.client_terminated = True
if not self._started_closing_handshake:
self._write_frame(True, 0x8, b(""))
self.stream.close()
elif opcode == 0x9:
# Ping
self._write_frame(True, 0xA, data)
elif opcode == 0xA:
# Pong
pass
else:
self._abort()
def close(self):
"""Closes the WebSocket connection."""
self._write_frame(True, 0x8, b(""))
self._started_closing_handshake = True
self._waiting = tornado.ioloop.IOLoop.instance().add_timeout(time.time() + 5, self._abort)