import base64
import gzip
import importlib
import io
import logging
import secrets
import urllib
import zlib
from . import exceptions
from . import packet
from . import payload
from . import socket
default_logger = logging.getLogger('engineio.server')
class Server(object):
"""An Engine.IO server.
This class implements a fully compliant Engine.IO web server with support
for websocket and long-polling transports.
:param async_mode: The asynchronous model to use. See the Deployment
section in the documentation for a description of the
available options. Valid async modes are "threading",
"eventlet", "gevent" and "gevent_uwsgi". If this
argument is not given, "eventlet" is tried first, then
"gevent_uwsgi", then "gevent", and finally "threading".
The first async mode that has all its dependencies
installed is the one that is chosen.
:param ping_interval: The interval in seconds at which the server pings
the client. The default is 25 seconds. For advanced
control, a two element tuple can be given, where
the first number is the ping interval and the second
is a grace period added by the server.
:param ping_timeout: The time in seconds that the client waits for the
server to respond before disconnecting. The default
is 5 seconds.
:param max_http_buffer_size: The maximum size of a message when using the
polling transport. The default is 1,000,000
bytes.
:param allow_upgrades: Whether to allow transport upgrades or not. The
default is ``True``.
:param http_compression: Whether to compress packages when using the
polling transport. The default is ``True``.
:param compression_threshold: Only compress messages when their byte size
is greater than this value. The default is
1024 bytes.
:param cookie: If set to a string, it is the name of the HTTP cookie the
server sends back tot he client containing the client
session id. If set to a dictionary, the ``'name'`` key
contains the cookie name and other keys define cookie
attributes, where the value of each attribute can be a
string, a callable with no arguments, or a boolean. If set
to ``None`` (the default), a cookie is not sent to the
client.
:param cors_allowed_origins: Origin or list of origins that are allowed to
connect to this server. Only the same origin
is allowed by default. Set this argument to
``'*'`` to allow all origins, or to ``[]`` to
disable CORS handling.
:param cors_credentials: Whether credentials (cookies, authentication) are
allowed in requests to this server. The default
is ``True``.
:param logger: To enable logging set to ``True`` or pass a logger object to
use. To disable logging set to ``False``. The default is
``False``. Note that fatal errors are logged even when
``logger`` is ``False``.
:param json: An alternative json module to use for encoding and decoding
packets. Custom json modules must have ``dumps`` and ``loads``
functions that are compatible with the standard library
versions.
:param async_handlers: If set to ``True``, run message event handlers in
non-blocking threads. To run handlers synchronously,
set to ``False``. The default is ``True``.
:param monitor_clients: If set to ``True``, a background task will ensure
inactive clients are closed. Set to ``False`` to
disable the monitoring task (not recommended). The
default is ``True``.
:param kwargs: Reserved for future extensions, any additional parameters
given as keyword arguments will be silently ignored.
"""
compression_methods = ['gzip', 'deflate']
event_names = ['connect', 'disconnect', 'message']
_default_monitor_clients = True
sequence_number = 0
def __init__(self, async_mode=None, ping_interval=25, ping_timeout=5,
max_http_buffer_size=1000000, allow_upgrades=True,
http_compression=True, compression_threshold=1024,
cookie=None, cors_allowed_origins=None,
cors_credentials=True, logger=False, json=None,
async_handlers=True, monitor_clients=None, **kwargs):
self.ping_timeout = ping_timeout
if isinstance(ping_interval, tuple):
self.ping_interval = ping_interval[0]
self.ping_interval_grace_period = ping_interval[1]
else:
self.ping_interval = ping_interval
self.ping_interval_grace_period = 0
self.max_http_buffer_size = max_http_buffer_size
self.allow_upgrades = allow_upgrades
self.http_compression = http_compression
self.compression_threshold = compression_threshold
self.cookie = cookie
self.cors_allowed_origins = cors_allowed_origins
self.cors_credentials = cors_credentials
self.async_handlers = async_handlers
self.sockets = {}
self.handlers = {}
self.log_message_keys = set()
self.start_service_task = monitor_clients \
if monitor_clients is not None else self._default_monitor_clients
if json is not None:
packet.Packet.json = json
if not isinstance(logger, bool):
self.logger = logger
else:
self.logger = default_logger
if self.logger.level == logging.NOTSET:
if logger:
self.logger.setLevel(logging.INFO)
else:
self.logger.setLevel(logging.ERROR)
self.logger.addHandler(logging.StreamHandler())
modes = self.async_modes()
if async_mode is not None:
modes = [async_mode] if async_mode in modes else []
self._async = None
self.async_mode = None
for mode in modes:
try:
self._async = importlib.import_module(
'engineio.async_drivers.' + mode)._async
asyncio_based = self._async['asyncio'] \
if 'asyncio' in self._async else False
if asyncio_based != self.is_asyncio_based():
continue # pragma: no cover
self.async_mode = mode
break
except ImportError:
pass
if self.async_mode is None:
raise ValueError('Invalid async_mode specified')
if self.is_asyncio_based() and \
('asyncio' not in self._async or not
self._async['asyncio']): # pragma: no cover
raise ValueError('The selected async_mode is not asyncio '
'compatible')
if not self.is_asyncio_based() and 'asyncio' in self._async and \
self._async['asyncio']: # pragma: no cover
raise ValueError('The selected async_mode requires asyncio and '
'must use the AsyncServer class')
self.logger.info('Server initialized for %s.', self.async_mode)
def is_asyncio_based(self):
return False
def async_modes(self):
return ['eventlet', 'gevent_uwsgi', 'gevent', 'threading']
def on(self, event, handler=None):
"""Register an event handler.
:param event: The event name. Can be ``'connect'``, ``'message'`` or
``'disconnect'``.
:param handler: The function that should be invoked to handle the
event. When this parameter is not given, the method
acts as a decorator for the handler function.
Example usage::
# as a decorator:
@eio.on('connect')
def connect_handler(sid, environ):
print('Connection request')
if environ['REMOTE_ADDR'] in blacklisted:
return False # reject
# as a method:
def message_handler(sid, msg):
print('Received message: ', msg)
eio.send(sid, 'response')
eio.on('message', message_handler)
The handler function receives the ``sid`` (session ID) for the
client as first argument. The ``'connect'`` event handler receives the
WSGI environment as a second argument, and can return ``False`` to
reject the connection. The ``'message'`` handler receives the message
payload as a second argument. The ``'disconnect'`` handler does not
take a second argument.
"""
if event not in self.event_names:
raise ValueError('Invalid event')
def set_handler(handler):
self.handlers[event] = handler
return handler
if handler is None:
return set_handler
set_handler(handler)
def send(self, sid, data):
"""Send a message to a client.
:param sid: The session id of the recipient client.
:param data: The data to send to the client. Data can be of type
``str``, ``bytes``, ``list`` or ``dict``. If a ``list``
or ``dict``, the data will be serialized as JSON.
"""
try:
socket = self._get_socket(sid)
except KeyError:
# the socket is not available
self.logger.warning('Cannot send to sid %s', sid)
return
socket.send(packet.Packet(packet.MESSAGE, data=data))
def get_session(self, sid):
"""Return the user session for a client.
:param sid: The session id of the client.
The return value is a dictionary. Modifications made to this
dictionary are not guaranteed to be preserved unless
``save_session()`` is called, or when the ``session`` context manager
is used.
"""
socket = self._get_socket(sid)
return socket.session
def save_session(self, sid, session):
"""Store the user session for a client.
:param sid: The session id of the client.
:param session: The session dictionary.
"""
socket = self._get_socket(sid)
socket.session = session
def session(self, sid):
"""Return the user session for a client with context manager syntax.
:param sid: The session id of the client.
This is a context manager that returns the user session dictionary for
the client. Any changes that are made to this dictionary inside the
context manager block are saved back to the session. Example usage::
@eio.on('connect')
def on_connect(sid, environ):
username = authenticate_user(environ)
if not username:
return False
with eio.session(sid) as session:
session['username'] = username
@eio.on('message')
def on_message(sid, msg):
with eio.session(sid) as session:
print('received message from ', session['username'])
"""
class _session_context_manager(object):
def __init__(self, server, sid):
self.server = server
self.sid = sid
self.session = None
def __enter__(self):
self.session = self.server.get_session(sid)
return self.session
def __exit__(self, *args):
self.server.save_session(sid, self.session)
return _session_context_manager(self, sid)
def disconnect(self, sid=None):
"""Disconnect a client.
:param sid: The session id of the client to close. If this parameter
is not given, then all clients are closed.
"""
if sid is not None:
try:
socket = self._get_socket(sid)
except KeyError: # pragma: no cover
# the socket was already closed or gone
pass
else:
socket.close()
if sid in self.sockets: # pragma: no cover
del self.sockets[sid]
else:
for client in self.sockets.values():
client.close()
self.sockets = {}
def transport(self, sid):
"""Return the name of the transport used by the client.
The two possible values returned by this function are ``'polling'``
and ``'websocket'``.
:param sid: The session of the client.
"""
return 'websocket' if self._get_socket(sid).upgraded else 'polling'
def handle_request(self, environ, start_response):
"""Handle an HTTP request from the client.
This is the entry point of the Engine.IO application, using the same
interface as a WSGI application. For the typical usage, this function
is invoked by the :class:`Middleware` instance, but it can be invoked
directly when the middleware is not used.
:param environ: The WSGI environment.
:param start_response: The WSGI ``start_response`` function.
This function returns the HTTP response body to deliver to the client
as a byte sequence.
"""
if self.cors_allowed_origins != []:
# Validate the origin header if present
# This is important for WebSocket more than for HTTP, since
# browsers only apply CORS controls to HTTP.
origin = environ.get('HTTP_ORIGIN')
if origin:
allowed_origins = self._cors_allowed_origins(environ)
if allowed_origins is not None and origin not in \
allowed_origins:
self._log_error_once(
origin + ' is not an accepted origin.', 'bad-origin')
r = self._bad_request(
origin + ' is not an accepted origin.')
start_response(r['status'], r['headers'])
return [r['response']]
method = environ['REQUEST_METHOD']
query = urllib.parse.parse_qs(environ.get('QUERY_STRING', ''))
jsonp = False
jsonp_index = None
# make sure the client speaks a compatible Engine.IO version
sid = query['sid'][0] if 'sid' in query else None
if sid is None and query.get('EIO') != ['4']:
self._log_error_once(
'The client is using an unsupported version of the Socket.IO '
'or Engine.IO protocols', 'bad-version')
r = self._bad_request(
'The client is using an unsupported version of the Socket.IO '
'or Engine.IO protocols')
start_response(r['status'], r['headers'])
return [r['response']]
if 'j' in query:
jsonp = True
try:
jsonp_index = int(query['j'][0])
except (ValueError, KeyError, IndexError):
# Invalid JSONP index number
pass
if jsonp and jsonp_index is None:
self._log_error_once('Invalid JSONP index number',
'bad-jsonp-index')
r = self._bad_request('Invalid JSONP index number')
elif method == 'GET':
if sid is None:
transport = query.get('transport', ['polling'])[0]
# transport must be one of 'polling' or 'websocket'.
# if 'websocket', the HTTP_UPGRADE header must match.
upgrade_header = environ.get('HTTP_UPGRADE').lower() \
if 'HTTP_UPGRADE' in environ else None
if transport == 'polling' \
or transport == upgrade_header == 'websocket':
r = self._handle_connect(environ, start_response,
transport, jsonp_index)
else:
self._log_error_once('Invalid transport ' + transport,
'bad-transport')
r = self._bad_request('Invalid transport ' + transport)
else:
if sid not in self.sockets:
self._log_error_once('Invalid session ' + sid, 'bad-sid')
r = self._bad_request('Invalid session ' + sid)
else:
socket = self._get_socket(sid)
try:
packets = socket.handle_get_request(
environ, start_response)
if isinstance(packets, list):
r = self._ok(packets, jsonp_index=jsonp_index)
else:
r = packets
except exceptions.EngineIOError:
if sid in self.sockets: # pragma: no cover
self.disconnect(sid)
r = self._bad_request()
if sid in self.sockets and self.sockets[sid].closed:
del self.sockets[sid]
elif method == 'POST':
if sid is None or sid not in self.sockets:
self._log_error_once('Invalid session ' + sid, 'bad-sid')
r = self._bad_request('Invalid session ' + sid)
else:
socket = self._get_socket(sid)
try:
socket.handle_post_request(environ)
r = self._ok(jsonp_index=jsonp_index)
except exceptions.EngineIOError:
if sid in self.sockets: # pragma: no cover
self.disconnect(sid)
r = self._bad_request()
except: # pragma: no cover
# for any other unexpected errors, we log the error
# and keep going
self.logger.exception('post request handler error')
r = self._ok(jsonp_index=jsonp_index)
elif method == 'OPTIONS':
r = self._ok()
else:
self.logger.warning('Method %s not supported', method)
r = self._method_not_found()
if not isinstance(r, dict):
return r or []
if self.http_compression and \
len(r['response']) >= self.compression_threshold:
encodings = [e.split(';')[0].strip() for e in
environ.get('HTTP_ACCEPT_ENCODING', '').split(',')]
for encoding in encodings:
if encoding in self.compression_methods:
r['response'] = \
getattr(self, '_' + encoding)(r['response'])
r['headers'] += [('Content-Encoding', encoding)]
break
cors_headers = self._cors_headers(environ)
start_response(r['status'], r['headers'] + cors_headers)
return [r['response']]
def start_background_task(self, target, *args, **kwargs):
"""Start a background task using the appropriate async model.
This is a utility function that applications can use to start a
background task using the method that is compatible with the
selected async mode.
:param target: the target function to execute.
:param args: arguments to pass to the function.
:param kwargs: keyword arguments to pass to the function.
This function returns an object compatible with the `Thread` class in
the Python standard library. The `start()` method on this object is
already called by this function.
"""
th = self._async['thread'](target=target, args=args, kwargs=kwargs)
th.start()
return th # pragma: no cover
def sleep(self, seconds=0):
"""Sleep for the requested amount of time using the appropriate async
model.
This is a utility function that applications can use to put a task to
sleep without having to worry about using the correct call for the
selected async mode.
"""
return self._async['sleep'](seconds)
def create_queue(self, *args, **kwargs):
"""Create a queue object using the appropriate async model.
This is a utility function that applications can use to create a queue
without having to worry about using the correct call for the selected
async mode.
"""
return self._async['queue'](*args, **kwargs)
def get_queue_empty_exception(self):
"""Return the queue empty exception for the appropriate async model.
This is a utility function that applications can use to work with a
queue without having to worry about using the correct call for the
selected async mode.
"""
return self._async['queue_empty']
def create_event(self, *args, **kwargs):
"""Create an event object using the appropriate async model.
This is a utility function that applications can use to create an
event without having to worry about using the correct call for the
selected async mode.
"""
return self._async['event'](*args, **kwargs)
def generate_id(self):
"""Generate a unique session id."""
id = base64.b64encode(
secrets.token_bytes(12) + self.sequence_number.to_bytes(3, 'big'))
self.sequence_number = (self.sequence_number + 1) & 0xffffff
return id.decode('utf-8').replace('/', '_').replace('+', '-')
def _generate_sid_cookie(self, sid, attributes):
"""Generate the sid cookie."""
cookie = attributes.get('name', 'io') + '=' + sid
for attribute, value in attributes.items():
if attribute == 'name':
continue
if callable(value):
value = value()
if value is True:
cookie += '; ' + attribute
else:
cookie += '; ' + attribute + '=' + value
return cookie
def _handle_connect(self, environ, start_response, transport,
jsonp_index=None):
"""Handle a client connection request."""
if self.start_service_task:
# start the service task to monitor connected clients
self.start_service_task = False
self.start_background_task(self._service_task)
sid = self.generate_id()
s = socket.Socket(self, sid)
self.sockets[sid] = s
pkt = packet.Packet(packet.OPEN, {
'sid': sid,
'upgrades': self._upgrades(sid, transport),
'pingTimeout': int(self.ping_timeout * 1000),
'pingInterval': int(
self.ping_interval + self.ping_interval_grace_period) * 1000})
s.send(pkt)
s.schedule_ping()
# NOTE: some sections below are marked as "no cover" to workaround
# what seems to be a bug in the coverage package. All the lines below
# are covered by tests, but some are not reported as such for some
# reason
ret = self._trigger_event('connect', sid, environ, run_async=False)
if ret is not None and ret is not True: # pragma: no cover
del self.sockets[sid]
self.logger.warning('Application rejected connection')
return self._unauthorized(ret or None)
if transport == 'websocket': # pragma: no cover
ret = s.handle_get_request(environ, start_response)
if s.closed and sid in self.sockets:
# websocket connection ended, so we are done
del self.sockets[sid]
return ret
else: # pragma: no cover
s.connected = True
headers = None
if self.cookie:
if isinstance(self.cookie, dict):
headers = [(
'Set-Cookie',
self._generate_sid_cookie(sid, self.cookie)
)]
else:
headers = [(
'Set-Cookie',
self._generate_sid_cookie(sid, {
'name': self.cookie, 'path': '/', 'SameSite': 'Lax'
})
)]
try:
return self._ok(s.poll(), headers=headers,
jsonp_index=jsonp_index)
except exceptions.QueueEmpty:
return self._bad_request()
def _upgrades(self, sid, transport):
"""Return the list of possible upgrades for a client connection."""
if not self.allow_upgrades or self._get_socket(sid).upgraded or \
self._async['websocket'] is None or transport == 'websocket':
return []
return ['websocket']
def _trigger_event(self, event, *args, **kwargs):
"""Invoke an event handler."""
run_async = kwargs.pop('run_async', False)
if event in self.handlers:
if run_async:
return self.start_background_task(self.handlers[event], *args)
else:
try:
return self.handlers[event](*args)
except:
self.logger.exception(event + ' handler error')
if event == 'connect':
# if connect handler raised error we reject the
# connection
return False
def _get_socket(self, sid):
"""Return the socket object for a given session."""
try:
s = self.sockets[sid]
except KeyError:
raise KeyError('Session not found')
if s.closed:
del self.sockets[sid]
raise KeyError('Session is disconnected')
return s
def _ok(self, packets=None, headers=None, jsonp_index=None):
"""Generate a successful HTTP response."""
if packets is not None:
if headers is None:
headers = []
headers += [('Content-Type', 'text/plain; charset=UTF-8')]
return {'status': '200 OK',
'headers': headers,
'response': payload.Payload(packets=packets).encode(
jsonp_index=jsonp_index).encode('utf-8')}
else:
return {'status': '200 OK',
'headers': [('Content-Type', 'text/plain')],
'response': b'OK'}
def _bad_request(self, message=None):
"""Generate a bad request HTTP error response."""
if message is None:
message = 'Bad Request'
message = packet.Packet.json.dumps(message)
return {'status': '400 BAD REQUEST',
'headers': [('Content-Type', 'text/plain')],
'response': message.encode('utf-8')}
def _method_not_found(self):
"""Generate a method not found HTTP error response."""
return {'status': '405 METHOD NOT FOUND',
'headers': [('Content-Type', 'text/plain')],
'response': b'Method Not Found'}
def _unauthorized(self, message=None):
"""Generate a unauthorized HTTP error response."""
if message is None:
message = 'Unauthorized'
message = packet.Packet.json.dumps(message)
return {'status': '401 UNAUTHORIZED',
'headers': [('Content-Type', 'application/json')],
'response': message.encode('utf-8')}
def _cors_allowed_origins(self, environ):
default_origins = []
if 'wsgi.url_scheme' in environ and 'HTTP_HOST' in environ:
default_origins.append('{scheme}://{host}'.format(
scheme=environ['wsgi.url_scheme'], host=environ['HTTP_HOST']))
if 'HTTP_X_FORWARDED_HOST' in environ:
scheme = environ.get(
'HTTP_X_FORWARDED_PROTO',
environ['wsgi.url_scheme']).split(',')[0].strip()
default_origins.append('{scheme}://{host}'.format(
scheme=scheme, host=environ['HTTP_X_FORWARDED_HOST'].split(
',')[0].strip()))
if self.cors_allowed_origins is None:
allowed_origins = default_origins
elif self.cors_allowed_origins == '*':
allowed_origins = None
elif isinstance(self.cors_allowed_origins, str):
allowed_origins = [self.cors_allowed_origins]
else:
allowed_origins = self.cors_allowed_origins
return allowed_origins
def _cors_headers(self, environ):
"""Return the cross-origin-resource-sharing headers."""
if self.cors_allowed_origins == []:
# special case, CORS handling is completely disabled
return []
headers = []
allowed_origins = self._cors_allowed_origins(environ)
if 'HTTP_ORIGIN' in environ and \
(allowed_origins is None or environ['HTTP_ORIGIN'] in
allowed_origins):
headers = [('Access-Control-Allow-Origin', environ['HTTP_ORIGIN'])]
if environ['REQUEST_METHOD'] == 'OPTIONS':
headers += [('Access-Control-Allow-Methods', 'OPTIONS, GET, POST')]
if 'HTTP_ACCESS_CONTROL_REQUEST_HEADERS' in environ:
headers += [('Access-Control-Allow-Headers',
environ['HTTP_ACCESS_CONTROL_REQUEST_HEADERS'])]
if self.cors_credentials:
headers += [('Access-Control-Allow-Credentials', 'true')]
return headers
def _gzip(self, response):
"""Apply gzip compression to a response."""
bytesio = io.BytesIO()
with gzip.GzipFile(fileobj=bytesio, mode='w') as gz:
gz.write(response)
return bytesio.getvalue()
def _deflate(self, response):
"""Apply deflate compression to a response."""
return zlib.compress(response)
def _log_error_once(self, message, message_key):
"""Log message with logging.ERROR level the first time, then log
with given level."""
if message_key not in self.log_message_keys:
self.logger.error(message + ' (further occurrences of this error '
'will be logged with level INFO)')
self.log_message_keys.add(message_key)
else:
self.logger.info(message)
def _service_task(self): # pragma: no cover
"""Monitor connected clients and clean up those that time out."""
while True:
if len(self.sockets) == 0:
# nothing to do
self.sleep(self.ping_timeout)
continue
# go through the entire client list in a ping interval cycle
sleep_interval = float(self.ping_timeout) / len(self.sockets)
try:
# iterate over the current clients
for s in self.sockets.copy().values():
if not s.closing and not s.closed:
s.check_ping_timeout()
self.sleep(sleep_interval)
except (SystemExit, KeyboardInterrupt):
self.logger.info('service task canceled')
break
except:
# an unexpected exception has occurred, log it and continue
self.logger.exception('service task exception')