import asyncio
import ssl
try:
import aiohttp
except ImportError: # pragma: no cover
aiohttp = None
import six
from . import client
from . import exceptions
from . import packet
from . import payload
class AsyncClient(client.Client):
"""An Engine.IO client for asyncio.
This class implements a fully compliant Engine.IO web client with support
for websocket and long-polling transports, compatible with the asyncio
framework on Python 3.5 or newer.
: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``.
: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 request_timeout: A timeout in seconds for requests. The default is
5 seconds.
:param ssl_verify: ``True`` to verify SSL certificates, or ``False`` to
skip SSL certificate verification, allowing
connections to servers with self signed certificates.
The default is ``True``.
"""
def is_asyncio_based(self):
return True
async def connect(self, url, headers={}, transports=None,
engineio_path='engine.io'):
"""Connect to an Engine.IO server.
:param url: The URL of the Engine.IO server. It can include custom
query string parameters if required by the server.
:param headers: A dictionary with custom headers to send with the
connection request.
:param transports: The list of allowed transports. Valid transports
are ``'polling'`` and ``'websocket'``. If not
given, the polling transport is connected first,
then an upgrade to websocket is attempted.
:param engineio_path: The endpoint where the Engine.IO server is
installed. The default value is appropriate for
most cases.
Note: this method is a coroutine.
Example usage::
eio = engineio.Client()
await eio.connect('http://localhost:5000')
"""
if self.state != 'disconnected':
raise ValueError('Client is not in a disconnected state')
valid_transports = ['polling', 'websocket']
if transports is not None:
if isinstance(transports, six.text_type):
transports = [transports]
transports = [transport for transport in transports
if transport in valid_transports]
if not transports:
raise ValueError('No valid transports provided')
self.transports = transports or valid_transports
self.queue = self.create_queue()
return await getattr(self, '_connect_' + self.transports[0])(
url, headers, engineio_path)
async def wait(self):
"""Wait until the connection with the server ends.
Client applications can use this function to block the main thread
during the life of the connection.
Note: this method is a coroutine.
"""
if self.read_loop_task:
await self.read_loop_task
async def send(self, data, binary=None):
"""Send a message to a 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.
:param binary: ``True`` to send packet as binary, ``False`` to send
as text. If not given, unicode (Python 2) and str
(Python 3) are sent as text, and str (Python 2) and
bytes (Python 3) are sent as binary.
Note: this method is a coroutine.
"""
await self._send_packet(packet.Packet(packet.MESSAGE, data=data,
binary=binary))
async def disconnect(self, abort=False):
"""Disconnect from the server.
:param abort: If set to ``True``, do not wait for background tasks
associated with the connection to end.
Note: this method is a coroutine.
"""
if self.state == 'connected':
await self._send_packet(packet.Packet(packet.CLOSE))
await self.queue.put(None)
self.state = 'disconnecting'
await self._trigger_event('disconnect', run_async=False)
if self.current_transport == 'websocket':
await self.ws.close()
if not abort:
await self.read_loop_task
self.state = 'disconnected'
try:
client.connected_clients.remove(self)
except ValueError: # pragma: no cover
pass
self._reset()
def start_background_task(self, target, *args, **kwargs):
"""Start a background task.
This is a utility function that applications can use to start a
background task.
: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.
Note: this method is a coroutine.
"""
return asyncio.ensure_future(target(*args, **kwargs))
async def sleep(self, seconds=0):
"""Sleep for the requested amount of time.
Note: this method is a coroutine.
"""
return await asyncio.sleep(seconds)
def create_queue(self):
"""Create a queue object."""
q = asyncio.Queue()
q.Empty = asyncio.QueueEmpty
return q
def create_event(self):
"""Create an event object."""
return asyncio.Event()
def _reset(self):
if self.http: # pragma: no cover
asyncio.ensure_future(self.http.close())
super()._reset()
async def _connect_polling(self, url, headers, engineio_path):
"""Establish a long-polling connection to the Engine.IO server."""
if aiohttp is None: # pragma: no cover
self.logger.error('aiohttp not installed -- cannot make HTTP '
'requests!')
return
self.base_url = self._get_engineio_url(url, engineio_path, 'polling')
self.logger.info('Attempting polling connection to ' + self.base_url)
r = await self._send_request(
'GET', self.base_url + self._get_url_timestamp(), headers=headers,
timeout=self.request_timeout)
if r is None:
self._reset()
raise exceptions.ConnectionError(
'Connection refused by the server')
if r.status < 200 or r.status >= 300:
raise exceptions.ConnectionError(
'Unexpected status code {} in server response'.format(
r.status))
try:
p = payload.Payload(encoded_payload=await r.read())
except ValueError:
six.raise_from(exceptions.ConnectionError(
'Unexpected response from server'), None)
open_packet = p.packets[0]
if open_packet.packet_type != packet.OPEN:
raise exceptions.ConnectionError(
'OPEN packet not returned by server')
self.logger.info(
'Polling connection accepted with ' + str(open_packet.data))
self.sid = open_packet.data['sid']
self.upgrades = open_packet.data['upgrades']
self.ping_interval = open_packet.data['pingInterval'] / 1000.0
self.ping_timeout = open_packet.data['pingTimeout'] / 1000.0
self.current_transport = 'polling'
self.base_url += '&sid=' + self.sid
self.state = 'connected'
client.connected_clients.append(self)
await self._trigger_event('connect', run_async=False)
for pkt in p.packets[1:]:
await self._receive_packet(pkt)
if 'websocket' in self.upgrades and 'websocket' in self.transports:
# attempt to upgrade to websocket
if await self._connect_websocket(url, headers, engineio_path):
# upgrade to websocket succeeded, we're done here
return
self.ping_loop_task = self.start_background_task(self._ping_loop)
self.write_loop_task = self.start_background_task(self._write_loop)
self.read_loop_task = self.start_background_task(
self._read_loop_polling)
async def _connect_websocket(self, url, headers, engineio_path):
"""Establish or upgrade to a WebSocket connection with the server."""
if aiohttp is None: # pragma: no cover
self.logger.error('aiohttp package not installed')
return False
websocket_url = self._get_engineio_url(url, engineio_path,
'websocket')
if self.sid:
self.logger.info(
'Attempting WebSocket upgrade to ' + websocket_url)
upgrade = True
websocket_url += '&sid=' + self.sid
else:
upgrade = False
self.base_url = websocket_url
self.logger.info(
'Attempting WebSocket connection to ' + websocket_url)
if self.http is None or self.http.closed: # pragma: no cover
self.http = aiohttp.ClientSession()
try:
if not self.ssl_verify:
ssl_context = ssl.create_default_context()
ssl_context.check_hostname = False
ssl_context.verify_mode = ssl.CERT_NONE
ws = await self.http.ws_connect(
websocket_url + self._get_url_timestamp(),
headers=headers, ssl=ssl_context)
else:
ws = await self.http.ws_connect(
websocket_url + self._get_url_timestamp(),
headers=headers)
except (aiohttp.client_exceptions.WSServerHandshakeError,
aiohttp.client_exceptions.ServerConnectionError):
if upgrade:
self.logger.warning(
'WebSocket upgrade failed: connection error')
return False
else:
raise exceptions.ConnectionError('Connection error')
if upgrade:
p = packet.Packet(packet.PING, data='probe').encode(
always_bytes=False)
try:
await ws.send_str(p)
except Exception as e: # pragma: no cover
self.logger.warning(
'WebSocket upgrade failed: unexpected send exception: %s',
str(e))
return False
try:
p = (await ws.receive()).data
except Exception as e: # pragma: no cover
self.logger.warning(
'WebSocket upgrade failed: unexpected recv exception: %s',
str(e))
return False
pkt = packet.Packet(encoded_packet=p)
if pkt.packet_type != packet.PONG or pkt.data != 'probe':
self.logger.warning(
'WebSocket upgrade failed: no PONG packet')
return False
p = packet.Packet(packet.UPGRADE).encode(always_bytes=False)
try:
await ws.send_str(p)
except Exception as e: # pragma: no cover
self.logger.warning(
'WebSocket upgrade failed: unexpected send exception: %s',
str(e))
return False
self.current_transport = 'websocket'
self.logger.info('WebSocket upgrade was successful')
else:
try:
p = (await ws.receive()).data
except Exception as e: # pragma: no cover
raise exceptions.ConnectionError(
'Unexpected recv exception: ' + str(e))
open_packet = packet.Packet(encoded_packet=p)
if open_packet.packet_type != packet.OPEN:
raise exceptions.ConnectionError('no OPEN packet')
self.logger.info(
'WebSocket connection accepted with ' + str(open_packet.data))
self.sid = open_packet.data['sid']
self.upgrades = open_packet.data['upgrades']
self.ping_interval = open_packet.data['pingInterval'] / 1000.0
self.ping_timeout = open_packet.data['pingTimeout'] / 1000.0
self.current_transport = 'websocket'
self.state = 'connected'
client.connected_clients.append(self)
await self._trigger_event('connect', run_async=False)
self.ws = ws
self.ping_loop_task = self.start_background_task(self._ping_loop)
self.write_loop_task = self.start_background_task(self._write_loop)
self.read_loop_task = self.start_background_task(
self._read_loop_websocket)
return True
async def _receive_packet(self, pkt):
"""Handle incoming packets from the server."""
packet_name = packet.packet_names[pkt.packet_type] \
if pkt.packet_type < len(packet.packet_names) else 'UNKNOWN'
self.logger.info(
'Received packet %s data %s', packet_name,
pkt.data if not isinstance(pkt.data, bytes) else '<binary>')
if pkt.packet_type == packet.MESSAGE:
await self._trigger_event('message', pkt.data, run_async=True)
elif pkt.packet_type == packet.PONG:
self.pong_received = True
elif pkt.packet_type == packet.CLOSE:
await self.disconnect(abort=True)
elif pkt.packet_type == packet.NOOP:
pass
else:
self.logger.error('Received unexpected packet of type %s',
pkt.packet_type)
async def _send_packet(self, pkt):
"""Queue a packet to be sent to the server."""
if self.state != 'connected':
return
await self.queue.put(pkt)
self.logger.info(
'Sending packet %s data %s',
packet.packet_names[pkt.packet_type],
pkt.data if not isinstance(pkt.data, bytes) else '<binary>')
async def _send_request(
self, method, url, headers=None, body=None,
timeout=None): # pragma: no cover
if self.http is None or self.http.closed:
self.http = aiohttp.ClientSession()
http_method = getattr(self.http, method.lower())
try:
if not self.ssl_verify:
return await http_method(
url, headers=headers, data=body,
timeout=aiohttp.ClientTimeout(total=timeout), ssl=False)
else:
return await http_method(
url, headers=headers, data=body,
timeout=aiohttp.ClientTimeout(total=timeout))
except (aiohttp.ClientError, asyncio.TimeoutError) as exc:
self.logger.info('HTTP %s request to %s failed with error %s.',
method, url, exc)
async def _trigger_event(self, event, *args, **kwargs):
"""Invoke an event handler."""
run_async = kwargs.pop('run_async', False)
ret = None
if event in self.handlers:
if asyncio.iscoroutinefunction(self.handlers[event]) is True:
if run_async:
return self.start_background_task(self.handlers[event],
*args)
else:
try:
ret = await self.handlers[event](*args)
except asyncio.CancelledError: # pragma: no cover
pass
except:
self.logger.exception(event + ' async handler error')
if event == 'connect':
# if connect handler raised error we reject the
# connection
return False
else:
if run_async:
async def async_handler():
return self.handlers[event](*args)
return self.start_background_task(async_handler)
else:
try:
ret = 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
return ret
async def _ping_loop(self):
"""This background task sends a PING to the server at the requested
interval.
"""
self.pong_received = True
if self.ping_loop_event is None:
self.ping_loop_event = self.create_event()
else:
self.ping_loop_event.clear()
while self.state == 'connected':
if not self.pong_received:
self.logger.info(
'PONG response has not been received, aborting')
if self.ws:
await self.ws.close()
await self.queue.put(None)
break
self.pong_received = False
await self._send_packet(packet.Packet(packet.PING))
try:
await asyncio.wait_for(self.ping_loop_event.wait(),
self.ping_interval)
except (asyncio.TimeoutError,
asyncio.CancelledError): # pragma: no cover
pass
self.logger.info('Exiting ping task')
async def _read_loop_polling(self):
"""Read packets by polling the Engine.IO server."""
while self.state == 'connected':
self.logger.info(
'Sending polling GET request to ' + self.base_url)
r = await self._send_request(
'GET', self.base_url + self._get_url_timestamp(),
timeout=max(self.ping_interval, self.ping_timeout) + 5)
if r is None:
self.logger.warning(
'Connection refused by the server, aborting')
await self.queue.put(None)
break
if r.status < 200 or r.status >= 300:
self.logger.warning('Unexpected status code %s in server '
'response, aborting', r.status)
await self.queue.put(None)
break
try:
p = payload.Payload(encoded_payload=await r.read())
except ValueError:
self.logger.warning(
'Unexpected packet from server, aborting')
await self.queue.put(None)
break
for pkt in p.packets:
await self._receive_packet(pkt)
self.logger.info('Waiting for write loop task to end')
await self.write_loop_task
self.logger.info('Waiting for ping loop task to end')
if self.ping_loop_event: # pragma: no cover
self.ping_loop_event.set()
await self.ping_loop_task
if self.state == 'connected':
await self._trigger_event('disconnect', run_async=False)
try:
client.connected_clients.remove(self)
except ValueError: # pragma: no cover
pass
self._reset()
self.logger.info('Exiting read loop task')
async def _read_loop_websocket(self):
"""Read packets from the Engine.IO WebSocket connection."""
while self.state == 'connected':
p = None
try:
p = (await self.ws.receive()).data
if p is None: # pragma: no cover
raise RuntimeError('WebSocket read returned None')
except aiohttp.client_exceptions.ServerDisconnectedError:
self.logger.info(
'Read loop: WebSocket connection was closed, aborting')
await self.queue.put(None)
break
except Exception as e:
self.logger.info(
'Unexpected error "%s", aborting', str(e))
await self.queue.put(None)
break
if isinstance(p, six.text_type): # pragma: no cover
p = p.encode('utf-8')
pkt = packet.Packet(encoded_packet=p)
await self._receive_packet(pkt)
self.logger.info('Waiting for write loop task to end')
await self.write_loop_task
self.logger.info('Waiting for ping loop task to end')
if self.ping_loop_event: # pragma: no cover
self.ping_loop_event.set()
await self.ping_loop_task
if self.state == 'connected':
await self._trigger_event('disconnect', run_async=False)
try:
client.connected_clients.remove(self)
except ValueError: # pragma: no cover
pass
self._reset()
self.logger.info('Exiting read loop task')
async def _write_loop(self):
"""This background task sends packages to the server as they are
pushed to the send queue.
"""
while self.state == 'connected':
# to simplify the timeout handling, use the maximum of the
# ping interval and ping timeout as timeout, with an extra 5
# seconds grace period
timeout = max(self.ping_interval, self.ping_timeout) + 5
packets = None
try:
packets = [await asyncio.wait_for(self.queue.get(), timeout)]
except (self.queue.Empty, asyncio.TimeoutError,
asyncio.CancelledError):
self.logger.error('packet queue is empty, aborting')
break
if packets == [None]:
self.queue.task_done()
packets = []
else:
while True:
try:
packets.append(self.queue.get_nowait())
except self.queue.Empty:
break
if packets[-1] is None:
packets = packets[:-1]
self.queue.task_done()
break
if not packets:
# empty packet list returned -> connection closed
break
if self.current_transport == 'polling':
p = payload.Payload(packets=packets)
r = await self._send_request(
'POST', self.base_url, body=p.encode(),
headers={'Content-Type': 'application/octet-stream'},
timeout=self.request_timeout)
for pkt in packets:
self.queue.task_done()
if r is None:
self.logger.warning(
'Connection refused by the server, aborting')
break
if r.status < 200 or r.status >= 300:
self.logger.warning('Unexpected status code %s in server '
'response, aborting', r.status)
self._reset()
break
else:
# websocket
try:
for pkt in packets:
if pkt.binary:
await self.ws.send_bytes(pkt.encode(
always_bytes=False))
else:
await self.ws.send_str(pkt.encode(
always_bytes=False))
self.queue.task_done()
except aiohttp.client_exceptions.ServerDisconnectedError:
self.logger.info(
'Write loop: WebSocket connection was closed, '
'aborting')
break
self.logger.info('Exiting write loop task')