class engineio.AsyncServer(async_mode=None, ping_interval=25, ping_timeout=20, 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, transports=None, **kwargs)

   An Engine.IO server for asyncio.

   This class implements a fully compliant Engine.IO web server with
   support for websocket and long-polling transports, compatible with
   the asyncio framework on Python 3.5 or newer.

   Parameters:
      * **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 "aiohttp",
        "sanic", "tornado" and "asgi". If this argument is not given,
        "aiohttp" is tried first, followed by "sanic", "tornado", and
        finally "asgi". The first async mode that has all its
        dependencies installed is the one that is chosen.

      * **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.

      * **ping_timeout** -- The time in seconds that the client waits
        for the server to respond before disconnecting. The default is
        20 seconds.

      * **max_http_buffer_size** -- The maximum size that is accepted
        for incoming messages.  The default is 1,000,000 bytes. In
        spite of its name, the value set in this argument is enforced
        for HTTP long-polling and WebSocket connections.

      * **allow_upgrades** -- Whether to allow transport upgrades or
        not.

      * **http_compression** -- Whether to compress packages when
        using the polling transport.

      * **compression_threshold** -- Only compress messages when their
        byte size is greater than this value.

      * **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.

      * **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 "'*'" or "['*']" to
        allow all origins, or to "[]" to disable CORS handling.

      * **cors_credentials** -- Whether credentials (cookies,
        authentication) are allowed in requests to this server.

      * **logger** -- To enable logging set to "True" or pass a logger
        object to use. To disable logging set to "False". Note that
        fatal errors are logged even when "logger" is "False".

      * **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. This is a process-wide setting, all
        instantiated servers and clients must use the same JSON
        module.

      * **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".

      * **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".

      * **transports** -- The list of allowed transports. Valid
        transports are "'polling'" and "'websocket'". Defaults to
        "['polling', 'websocket']".

      * **kwargs** -- Reserved for future extensions, any additional
        parameters given as keyword arguments will be silently
        ignored.

   attach(app, engineio_path='engine.io')

      Attach the Engine.IO server to an application.

   async send(sid, data)

      Send a message to a client.

      Parameters:
         * **sid** -- The session id of the recipient client.

         * **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.

      Note: this method is a coroutine.

   async send_packet(sid, pkt)

      Send a raw packet to a client.

      Parameters:
         * **sid** -- The session id of the recipient client.

         * **pkt** -- The packet to send to the client.

      Note: this method is a coroutine.

   async get_session(sid)

      Return the user session for a client.

      Parameters:
         **sid** -- The session id of the client.

      The return value is a dictionary. Modifications made to this
      dictionary are not guaranteed to be preserved. If you want to
      modify the user session, use the "session" context manager
      instead.

   async save_session(sid, session)

      Store the user session for a client.

      Parameters:
         * **sid** -- The session id of the client.

         * **session** -- The session dictionary.

   session(sid)

      Return the user session for a client with context manager
      syntax.

      Parameters:
         **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):
             async with eio.session(sid) as session:
                 print('received message from ', session['username'])

   async disconnect(sid=None)

      Disconnect a client.

      Parameters:
         **sid** -- The session id of the client to close. If this
         parameter is not given, then all clients are closed.

      Note: this method is a coroutine.

   async handle_request(*args, **kwargs)

      Handle an HTTP request from the client.

      This is the entry point of the Engine.IO application. This
      function returns the HTTP response to deliver to the client.

      Note: this method is a coroutine.

   async shutdown()

      Stop Socket.IO background tasks.

      This method stops background activity initiated by the Socket.IO
      server. It must be called before shutting down the web server.

   start_background_task(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.

      Parameters:
         * **target** -- the target function to execute.

         * **args** -- arguments to pass to the function.

         * **kwargs** -- keyword arguments to pass to the function.

      The return value is a "asyncio.Task" object.

   async sleep(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.

      Note: this method is a coroutine.

   create_queue(*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. For asyncio based async modes, this
      returns an instance of "asyncio.Queue".

   get_queue_empty_exception()

      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. For asyncio based async modes,
      this returns an instance of "asyncio.QueueEmpty".

   create_event(*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. For asyncio based async modes, this
      returns an instance of "asyncio.Event".

   generate_id()

      Generate a unique session id.

   on(event, handler=None)

      Register an event handler.

      Parameters:
         * **event** -- The event name. Can be "'connect'",
           "'message'" or "'disconnect'".

         * **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.

   class reason

      Disconnection reasons.

      CLIENT_DISCONNECT = 'client disconnect'

         Client-initiated disconnection.

      PING_TIMEOUT = 'ping timeout'

         Ping timeout.

      SERVER_DISCONNECT = 'server disconnect'

         Server-initiated disconnection.

      TRANSPORT_CLOSE = 'transport close'

         Transport close.

      TRANSPORT_ERROR = 'transport error'

         Transport error.

   transport(sid)

      Return the name of the transport used by the client.

      The two possible values returned by this function are
      "'polling'" and "'websocket'".

      Parameters:
         **sid** -- The session of the client.
