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"""This file provides a class for parsing/building frames of the WebSocket
protocol version HyBi 00 and Hixie 75.
Specification:
http://tools.ietf.org/html/draft-ietf-hybi-thewebsocketprotocol-00
"""
from mod_pywebsocket import common
from mod_pywebsocket._stream_base import BadOperationException
from mod_pywebsocket._stream_base import ConnectionTerminatedException
from mod_pywebsocket._stream_base import InvalidFrameException
from mod_pywebsocket._stream_base import StreamBase
from mod_pywebsocket._stream_base import UnsupportedFrameException
from mod_pywebsocket import util
class StreamHixie75(StreamBase):
"""A class for parsing/building frames of the WebSocket protocol version
HyBi 00 and Hixie 75.
"""
def __init__(self, request, enable_closing_handshake=False):
"""Construct an instance.
Args:
request: mod_python request.
enable_closing_handshake: to let StreamHixie75 perform closing
handshake as specified in HyBi 00, set
this option to True.
"""
StreamBase.__init__(self, request)
self._logger = util.get_class_logger(self)
self._enable_closing_handshake = enable_closing_handshake
self._request.client_terminated = False
self._request.server_terminated = False
def send_message(self, message, end=True, binary=False):
"""Send message.
Args:
message: unicode string to send.
binary: not used in hixie75.
Raises:
BadOperationException: when called on a server-terminated
connection.
"""
if not end:
raise BadOperationException(
'StreamHixie75 doesn\'t support send_message with end=False')
if binary:
raise BadOperationException(
'StreamHixie75 doesn\'t support send_message with binary=True')
if self._request.server_terminated:
raise BadOperationException(
'Requested send_message after sending out a closing handshake')
self._write(''.join(['\x00', message.encode('utf-8'), '\xff']))
def _read_payload_length_hixie75(self):
"""Reads a length header in a Hixie75 version frame with length.
Raises:
ConnectionTerminatedException: when read returns empty string.
"""
length = 0
while True:
b_str = self._read(1)
b = ord(b_str)
length = length * 128 + (b & 0x7f)
if (b & 0x80) == 0:
break
return length
def receive_message(self):
"""Receive a WebSocket frame and return its payload an unicode string.
Returns:
payload unicode string in a WebSocket frame.
Raises:
ConnectionTerminatedException: when read returns empty
string.
BadOperationException: when called on a client-terminated
connection.
"""
if self._request.client_terminated:
raise BadOperationException(
'Requested receive_message after receiving a closing '
'handshake')
while True:
# Read 1 byte.
# mp_conn.read will block if no bytes are available.
# Timeout is controlled by TimeOut directive of Apache.
frame_type_str = self.receive_bytes(1)
frame_type = ord(frame_type_str)
if (frame_type & 0x80) == 0x80:
# The payload length is specified in the frame.
# Read and discard.
length = self._read_payload_length_hixie75()
if length > 0:
_ = self.receive_bytes(length)
# 5.3 3. 12. if /type/ is 0xFF and /length/ is 0, then set the
# /client terminated/ flag and abort these steps.
if not self._enable_closing_handshake:
continue
if frame_type == 0xFF and length == 0:
self._request.client_terminated = True
if self._request.server_terminated:
self._logger.debug(
'Received ack for server-initiated closing '
'handshake')
return None
self._logger.debug(
'Received client-initiated closing handshake')
self._send_closing_handshake()
self._logger.debug(
'Sent ack for client-initiated closing handshake')
return None
else:
# The payload is delimited with \xff.
bytes = self._read_until('\xff')
# The WebSocket protocol section 4.4 specifies that invalid
# characters must be replaced with U+fffd REPLACEMENT
# CHARACTER.
message = bytes.decode('utf-8', 'replace')
if frame_type == 0x00:
return message
# Discard data of other types.
def _send_closing_handshake(self):
if not self._enable_closing_handshake:
raise BadOperationException(
'Closing handshake is not supported in Hixie 75 protocol')
self._request.server_terminated = True
# 5.3 the server may decide to terminate the WebSocket connection by
# running through the following steps:
# 1. send a 0xFF byte and a 0x00 byte to the client to indicate the
# start of the closing handshake.
self._write('\xff\x00')
def close_connection(self, unused_code='', unused_reason=''):
"""Closes a WebSocket connection.
Raises:
ConnectionTerminatedException: when closing handshake was
not successfull.
"""
if self._request.server_terminated:
self._logger.debug(
'Requested close_connection but server is already terminated')
return
if not self._enable_closing_handshake:
self._request.server_terminated = True
self._logger.debug('Connection closed')
return
self._send_closing_handshake()
self._logger.debug('Sent server-initiated closing handshake')
# TODO(ukai): 2. wait until the /client terminated/ flag has been set,
# or until a server-defined timeout expires.
#
# For now, we expect receiving closing handshake right after sending
# out closing handshake, and if we couldn't receive non-handshake
# frame, we take it as ConnectionTerminatedException.
message = self.receive_message()
if message is not None:
raise ConnectionTerminatedException(
'Didn\'t receive valid ack for closing handshake')
# TODO: 3. close the WebSocket connection.
# note: mod_python Connection (mp_conn) doesn't have close method.
def send_ping(self, body):
raise BadOperationException(
'StreamHixie75 doesn\'t support send_ping')
# vi:sts=4 sw=4 et