text: """
      SleekXMPP: The Sleek XMPP Library
      Copyright (C) 2010  Nathanael C. Fritz
      This file is part of SleekXMPP.
  
      See the file LICENSE for copying permission.
  """
  
  from __future__ import with_statement, unicode_literals
  
  import base64
  import copy
  import logging
  import signal
  import socket as Socket
  import ssl
  import sys
  import threading
  import time
  import types
  import random
  import weakref
  try:
      import queue
  except ImportError:
      import Queue as queue
  
  import sleekxmpp
  from sleekxmpp.thirdparty.statemachine import StateMachine
  from sleekxmpp.xmlstream import Scheduler, tostring
  from sleekxmpp.xmlstream.stanzabase import StanzaBase, ET
  from sleekxmpp.xmlstream.handler import Waiter, XMLCallback
  from sleekxmpp.xmlstream.matcher import MatchXMLMask
  
  # In Python 2.x, file socket objects are broken. A patched socket
  # wrapper is provided for this case in filesocket.py.
  if sys.version_info < (3, 0):
      from sleekxmpp.xmlstream.filesocket import FileSocket, Socket26
  
  try:
      import dns.resolver
  except ImportError:
      DNSPYTHON = False
  else:
      DNSPYTHON = True
  
  
  # The time in seconds to wait before timing out waiting for response stanzas.
  RESPONSE_TIMEOUT = 30
  
  # The time in seconds to wait for events from the event queue, and also the
  # time between checks for the process stop signal.
  WAIT_TIMEOUT = 1
  
  # The number of threads to use to handle XML stream events. This is not the
  # same as the number of custom event handling threads. HANDLER_THREADS must
  # be at least 1.
  HANDLER_THREADS = 1
  
  # Flag indicating if the SSL library is available for use.
  SSL_SUPPORT = True
  
  # Maximum time to delay between connection attempts is one hour.
  RECONNECT_MAX_DELAY = 600
  
  log = logging.getLogger(__name__)
  
  
  class RestartStream(Exception):
      """
      Exception to restart stream processing, including
      resending the stream header.
      """
  
  
  class XMLStream(object):
      """
      An XML stream connection manager and event dispatcher.
  
      The XMLStream class abstracts away the issues of establishing a
      connection with a server and sending and receiving XML "stanzas".
      A stanza is a complete XML element that is a direct child of a root
      document element. Two streams are used, one for each communication
      direction, over the same socket. Once the connection is closed, both
      streams should be complete and valid XML documents.
  
      Three types of events are provided to manage the stream:
          Stream    -- Triggered based on received stanzas, similar in concept
                       to events in a SAX XML parser.
          Custom    -- Triggered manually.
          Scheduled -- Triggered based on time delays.
  
      Typically, stanzas are first processed by a stream event handler which
      will then trigger custom events to continue further processing,
      especially since custom event handlers may run in individual threads.
  
  
      Attributes:
          address       -- The hostname and port of the server.
          default_ns    -- The default XML namespace that will be applied
                           to all non-namespaced stanzas.
          event_queue   -- A queue of stream, custom, and scheduled
                           events to be processed.
          filesocket    -- A filesocket created from the main connection socket.
                           Required for ElementTree.iterparse.
          default_port  -- Default port to connect to.
          namespace_map -- Optional mapping of namespaces to namespace prefixes.
          scheduler     -- A scheduler object for triggering events
                           after a given period of time.
          send_queue    -- A queue of stanzas to be sent on the stream.
          socket        -- The connection to the server.
          ssl_support   -- Indicates if a SSL library is available for use.
          ssl_version   -- The version of the SSL protocol to use.
                           Defaults to ssl.PROTOCOL_TLSv1.
          ca_certs      -- File path to a CA certificate to verify the
                           server's identity.
          state         -- A state machine for managing the stream's
                           connection state.
          stream_footer -- The start tag and any attributes for the stream's
                           root element.
          stream_header -- The closing tag of the stream's root element.
          use_ssl       -- Flag indicating if SSL should be used.
          use_tls       -- Flag indicating if TLS should be used.
          use_proxy     -- Flag indicating that an HTTP Proxy should be used.
          stop          -- threading Event used to stop all threads.
          proxy_config  -- An optional dictionary with the following entries:
                              host     -- The host offering proxy services.
                              port     -- The port for the proxy service.
                              username -- Optional username for the proxy.
                              password -- Optional password for the proxy.
  
          auto_reconnect      -- Flag to determine whether we auto reconnect.
          reconnect_max_delay -- Maximum time to delay between connection
                                 attempts. Defaults to RECONNECT_MAX_DELAY,
                                 which is one hour.
          dns_answers     -- List of dns answers not yet used to connect.
  
      Methods:
          add_event_handler    -- Add a handler for a custom event.
          add_handler          -- Shortcut method for registerHandler.
          connect              -- Connect to the given server.
          del_event_handler    -- Remove a handler for a custom event.
          disconnect           -- Disconnect from the server and terminate
                                  processing.
          event                -- Trigger a custom event.
          get_id               -- Return the current stream ID.
          incoming_filter      -- Optionally filter stanzas before processing.
          new_id               -- Generate a new, unique ID value.
          process              -- Read XML stanzas from the stream and apply
                                  matching stream handlers.
          reconnect            -- Reestablish a connection to the server.
          register_handler     -- Add a handler for a stream event.
          register_stanza      -- Add a new stanza object type that may appear
                                  as a direct child of the stream's root.
          remove_handler       -- Remove a stream handler.
          remove_stanza        -- Remove a stanza object type.
          schedule             -- Schedule an event handler to execute after a
                                  given delay.
          send                 -- Send a stanza object on the stream.
          send_raw             -- Send a raw string on the stream.
          send_xml             -- Send an XML string on the stream.
          set_socket           -- Set the stream's socket and generate a new
                                  filesocket.
          start_stream_handler -- Perform any stream initialization such
                                  as handshakes.
          start_tls            -- Establish a TLS connection and restart
                                  the stream.
      """
  
      def __init__(self, socket=None, host='', port=0):
          """
          Establish a new XML stream.
  
          Arguments:
              socket -- Use an existing socket for the stream.
                        Defaults to None to generate a new socket.
              host   -- The name of the target server.
                        Defaults to the empty string.
              port   -- The port to use for the connection.
                        Defaults to 0.
          """
          self.ssl_support = SSL_SUPPORT
          self.ssl_version = ssl.PROTOCOL_TLSv1
          self.ca_certs = None
  
          self.wait_timeout = WAIT_TIMEOUT
          self.response_timeout = RESPONSE_TIMEOUT
          self.reconnect_delay = None
          self.reconnect_max_delay = RECONNECT_MAX_DELAY
  
          self.state = StateMachine(('disconnected', 'connected'))
          self.state._set_state('disconnected')
  
          self.default_port = int(port)
          self.default_domain = ''
          self.address = (host, int(port))
          self.filesocket = None
          self.set_socket(socket)
  
          if sys.version_info < (3, 0):
              self.socket_class = Socket26
          else:
              self.socket_class = Socket.socket
  
          self.use_ssl = False
          self.use_tls = False
          self.use_proxy = False
  
          self.proxy_config = {}
  
          self.default_ns = ''
          self.stream_ns = ''
          self.stream_header = "<stream>"
          self.stream_footer = "</stream>"
  
          self.whitespace_keepalive = True
          self.whitespace_keepalive_interval = 300
  
          self.stop = threading.Event()
          self.stream_end_event = threading.Event()
          self.stream_end_event.set()
          self.session_started_event = threading.Event()
          self.session_timeout = 45
  
          self.event_queue = queue.Queue()
          self.send_queue = queue.Queue()
          self.__failed_send_stanza = None
          self.scheduler = Scheduler(self.stop)
  
          self.namespace_map = {StanzaBase.xml_ns: 'xml'}
  
          self.__thread = {}
          self.__root_stanza = []
          self.__handlers = []
          self.__event_handlers = {}
          self.__event_handlers_lock = threading.Lock()
  
          self._id = 0
          self._id_lock = threading.Lock()
  
          self.auto_reconnect = True
          self.dns_answers = []
  
          self.add_event_handler('connected', self._handle_connected)
          self.add_event_handler('session_start', self._start_keepalive)
          self.add_event_handler('session_end', self._end_keepalive)
  
      def use_signals(self, signals=None):
          """
          Register signal handlers for SIGHUP and SIGTERM, if possible,
          which will raise a "killed" event when the application is
          terminated.
  
          If a signal handler already existed, it will be executed first,
          before the "killed" event is raised.
  
          Arguments:
              signals -- A list of signal names to be monitored.
                         Defaults to ['SIGHUP', 'SIGTERM'].
          """
          if signals is None:
              signals = ['SIGHUP', 'SIGTERM']
  
          existing_handlers = {}
          for sig_name in signals:
              if hasattr(signal, sig_name):
                  sig = getattr(signal, sig_name)
                  handler = signal.getsignal(sig)
                  if handler:
                      existing_handlers[sig] = handler
  
          def handle_kill(signum, frame):
              """
              Capture kill event and disconnect cleanly after first
              spawning the "killed" event.
              """
  
              if signum in existing_handlers and \
                     existing_handlers[signum] != handle_kill:
                  existing_handlers[signum](signum, frame)
  
              self.event("killed", direct=True)
              self.disconnect()
  
          try:
              for sig_name in signals:
                  if hasattr(signal, sig_name):
                      sig = getattr(signal, sig_name)
                      signal.signal(sig, handle_kill)
              self.__signals_installed = True
          except:
              log.debug("Can not set interrupt signal handlers. " + \
                        "SleekXMPP is not running from a main thread.")
  
      def new_id(self):
          """
          Generate and return a new stream ID in hexadecimal form.
  
          Many stanzas, handlers, or matchers may require unique
          ID values. Using this method ensures that all new ID values
          are unique in this stream.
          """
          with self._id_lock:
              self._id += 1
              return self.get_id()
  
      def get_id(self):
          """
          Return the current unique stream ID in hexadecimal form.
          """
          return "%X" % self._id
  
      def connect(self, host='', port=0, use_ssl=False,
                  use_tls=True, reattempt=True):
          """
          Create a new socket and connect to the server.
  
          Setting reattempt to True will cause connection attempts to be made
          every second until a successful connection is established.
  
          Arguments:
              host      -- The name of the desired server for the connection.
              port      -- Port to connect to on the server.
              use_ssl   -- Flag indicating if SSL should be used.
              use_tls   -- Flag indicating if TLS should be used.
              reattempt -- Flag indicating if the socket should reconnect
                           after disconnections.
          """
          if host and port:
              self.address = (host, int(port))
          try:
              Socket.inet_aton(self.address[0])
          except Socket.error:
              self.default_domain = self.address[0]
  
          # Respect previous SSL and TLS usage directives.
          if use_ssl is not None:
              self.use_ssl = use_ssl
          if use_tls is not None:
              self.use_tls = use_tls
  
          # Repeatedly attempt to connect until a successful connection
          # is established.
          connected = self.state.transition('disconnected', 'connected',
                                            func=self._connect)
          while reattempt and not connected:
              connected = self.state.transition('disconnected', 'connected',
                                                func=self._connect)
          return connected
  
      def _connect(self):
          self.scheduler.remove('Session timeout check')
          self.stop.clear()
          if self.default_domain:
              self.address = self.pick_dns_answer(self.default_domain,
                                                  self.address[1])
          self.socket = self.socket_class(Socket.AF_INET, Socket.SOCK_STREAM)
          self.configure_socket()
  
          if self.reconnect_delay is None:
              delay = 1.0
          else:
              delay = min(self.reconnect_delay * 2, self.reconnect_max_delay)
              delay = random.normalvariate(delay, delay * 0.1)
              log.debug('Waiting %s seconds before connecting.' , delay)
              time.sleep(delay)
  
          if self.use_proxy:
              connected = self._connect_proxy()
              if not connected:
                  self.reconnect_delay = delay
                  return False
  
          if self.use_ssl and self.ssl_support:
              log.debug("Socket Wrapped for SSL")
              if self.ca_certs is None:
                  cert_policy = ssl.CERT_NONE
              else:
                  cert_policy = ssl.CERT_REQUIRED
  
              ssl_socket = ssl.wrap_socket(self.socket,
                                           ca_certs=self.ca_certs,
                                           cert_reqs=cert_policy)
  
              if hasattr(self.socket, 'socket'):
                  # We are using a testing socket, so preserve the top
                  # layer of wrapping.
                  self.socket.socket = ssl_socket
              else:
                  self.socket = ssl_socket
  
          try:
              if not self.use_proxy:
                  log.debug("Connecting to %s:%s" , self.address)
                  self.socket.connect(self.address)
  
              self.set_socket(self.socket, ignore=True)
              #this event is where you should set your application state
              self.event("connected", direct=True)
              self.reconnect_delay = 1.0
              return True
          except Socket.error as serr:
              error_msg = "Could not connect to %s:%s. Socket Error #%s: %s"
              self.event('socket_error', serr)
              log.error(error_msg % (self.address[0], self.address[1],
                                         serr.errno, serr.strerror))
              self.reconnect_delay = delay
              return False
  
      def _connect_proxy(self):
          """Attempt to connect using an HTTP Proxy."""
  
          # Extract the proxy address, and optional credentials
          address = (self.proxy_config['host'], int(self.proxy_config['port']))
          cred = None
          if self.proxy_config['username']:
              username = self.proxy_config['username']
              password = self.proxy_config['password']
  
              cred = '%s:%s' % (username, password)
              if sys.version_info < (3, 0):
                  cred = bytes(cred)
              else:
                  cred = bytes(cred, 'utf-8')
              cred = base64.b64encode(cred).decode('utf-8')
  
          # Build the HTTP headers for connecting to the XMPP server
          headers = ['CONNECT %s:%s HTTP/1.0' % self.address,
                     'Host: %s:%s' % self.address,
                     'Proxy-Connection: Keep-Alive',
                     'Pragma: no-cache',
                     'User-Agent: SleekXMPP/%s' % sleekxmpp.__version__]
          if cred:
              headers.append('Proxy-Authorization: Basic %s' % cred)
          headers = '\r\n'.join(headers) + '\r\n\r\n'
  
          try:
              log.debug("Connecting to proxy: %s:%s" , address)
              self.socket.connect(address)
              self.send_raw(headers, now=True)
              resp = ''
              while '\r\n\r\n' not in resp:
                  resp += self.socket.recv(1024).decode('utf-8')
              log.debug('RECV: %s' , resp)
  
              lines = resp.split('\r\n')
              if '200' not in lines[0]:
                  self.event('proxy_error', resp)
                  log.error('Proxy Error: %s' , lines[0])
                  return False
  
              # Proxy connection established, continue connecting
              # with the XMPP server.
              return True
          except Socket.error as serr:
              error_msg = "Could not connect to %s:%s. Socket Error #%s: %s"
              self.event('socket_error', serr)
              log.error(error_msg % (self.address[0], self.address[1],
                                         serr.errno, serr.strerror))
              return False
  
      def _handle_connected(self, event=None):
          """
          Add check to ensure that a session is established within
          a reasonable amount of time.
          """
  
          def _handle_session_timeout():
              if not self.session_started_event.isSet():
                  log.debug("Session start has taken more " + \
                            "than %d seconds" % self.session_timeout)
                  self.disconnect(reconnect=self.auto_reconnect)
  
          self.schedule("Session timeout check",
                  self.session_timeout,
                  _handle_session_timeout)
  
  
      def disconnect(self, reconnect=False, wait=False):
          """
          Terminate processing and close the XML streams.
  
          Optionally, the connection may be reconnected and
          resume processing afterwards.
  
          If the disconnect should take place after all items
          in the send queue have been sent, use wait=True. However,
          take note: If you are constantly adding items to the queue
          such that it is never empty, then the disconnect will
          not occur and the call will continue to block.
  
          Arguments:
              reconnect -- Flag indicating if the connection
                           and processing should be restarted.
                           Defaults to False.
              wait      -- Flag indicating if the send queue should
                           be emptied before disconnecting.
          """
          self.state.transition('connected', 'disconnected', wait=0.0,
                                func=self._disconnect, args=(reconnect, wait))
  
      def _disconnect(self, reconnect=False, wait=False):
          # Wait for the send queue to empty.
          if wait:
              self.send_queue.join()
  
          # Send the end of stream marker.
          self.send_raw(self.stream_footer, now=True)
          self.session_started_event.clear()
          # Wait for confirmation that the stream was
          # closed in the other direction.
          self.auto_reconnect = reconnect
          log.debug('Waiting for %s from server' , self.stream_footer)
          self.stream_end_event.wait(4)
          if not self.auto_reconnect:
              self.stop.set()
          try:
              self.socket.shutdown(Socket.SHUT_RDWR)
              self.socket.close()
              self.filesocket.close()
          except Socket.error as serr:
              self.event('socket_error', serr)
          finally:
              #clear your application state
              self.event('session_end', direct=True)
              self.event("disconnected", direct=True)
              return True
  
      def reconnect(self):
          """
          Reset the stream's state and reconnect to the server.
          """
          log.debug("reconnecting...")
          self.state.transition('connected', 'disconnected', wait=2.0,
                                func=self._disconnect, args=(True,))
  
          log.debug("connecting...")
          connected = self.state.transition('disconnected', 'connected',
                                            wait=2.0, func=self._connect)
          while not connected:
              connected = self.state.transition('disconnected', 'connected',
                                                wait=2.0, func=self._connect)
          return connected
  
      def set_socket(self, socket, ignore=False):
          """
          Set the socket to use for the stream.
  
          The filesocket will be recreated as well.
  
          Arguments:
              socket -- The new socket to use.
              ignore -- don't set the state
          """
          self.socket = socket
          if socket is not None:
              # ElementTree.iterparse requires a file.
              # 0 buffer files have to be binary.
  
              # Use the correct fileobject type based on the Python
              # version to work around a broken implementation in
              # Python 2.x.
              if sys.version_info < (3, 0):
                  self.filesocket = FileSocket(self.socket)
              else:
                  self.filesocket = self.socket.makefile('rb', 0)
              if not ignore:
                  self.state._set_state('connected')
  
      def configure_socket(self):
          """
          Set timeout and other options for self.socket.
  
          Meant to be overridden.
          """
          self.socket.settimeout(None)
  
      def configure_dns(self, resolver, domain=None, port=None):
          """
          Configure and set options for a dns.resolver.Resolver
          instance, and other DNS related tasks. For example, you
          can also check Socket.getaddrinfo to see if you need to
          call out to libresolv.so.2 to run res_init().
  
          Meant to be overridden.
  
          Arguments:
              resolver -- A dns.resolver.Resolver instance, or None
                          if dnspython is not installed.
              domain   -- The initial domain under consideration.
              port     -- The initial port under consideration.
          """
          pass
  
      def start_tls(self):
          """
          Perform handshakes for TLS.
  
          If the handshake is successful, the XML stream will need
          to be restarted.
          """
          if self.ssl_support:
              log.info("Negotiating TLS")
              log.info("Using SSL version: %s" , str(self.ssl_version))
              if self.ca_certs is None:
                  cert_policy = ssl.CERT_NONE
              else:
                  cert_policy = ssl.CERT_REQUIRED
  
              ssl_socket = ssl.wrap_socket(self.socket,
                                           ssl_version=self.ssl_version,
                                           do_handshake_on_connect=False,
                                           ca_certs=self.ca_certs,
                                           cert_reqs=cert_policy)
  
              if hasattr(self.socket, 'socket'):
                  # We are using a testing socket, so preserve the top
                  # layer of wrapping.
                  self.socket.socket = ssl_socket
              else:
                  self.socket = ssl_socket
              self.socket.do_handshake()
              self.set_socket(self.socket)
              return True
          else:
              log.warning("Tried to enable TLS, but ssl module not found.")
              return False
  
      def _start_keepalive(self, event):
          """
          Begin sending whitespace periodically to keep the connection alive.
  
          May be disabled by setting:
              self.whitespace_keepalive = False
  
          The keepalive interval can be set using:
              self.whitespace_keepalive_interval = 300
          """
  
          def send_keepalive():
              if self.send_queue.empty():
                  self.send_raw(' ')
  
          self.schedule('Whitespace Keepalive',
                        self.whitespace_keepalive_interval,
                        send_keepalive,
                        repeat=True)
  
      def _end_keepalive(self, event):
          """Stop sending whitespace keepalives"""
          self.scheduler.remove('Whitespace Keepalive')
  
      def start_stream_handler(self, xml):
          """
          Perform any initialization actions, such as handshakes, once the
          stream header has been sent.
  
          Meant to be overridden.
          """
          pass
  
      def register_stanza(self, stanza_class):
          """
          Add a stanza object class as a known root stanza. A root stanza is
          one that appears as a direct child of the stream's root element.
  
          Stanzas that appear as substanzas of a root stanza do not need to
          be registered here. That is done using register_stanza_plugin() from
          sleekxmpp.xmlstream.stanzabase.
  
          Stanzas that are not registered will not be converted into
          stanza objects, but may still be processed using handlers and
          matchers.
  
          Arguments:
              stanza_class -- The top-level stanza object's class.
          """
          self.__root_stanza.append(stanza_class)
  
      def remove_stanza(self, stanza_class):
          """
          Remove a stanza from being a known root stanza. A root stanza is
          one that appears as a direct child of the stream's root element.
  
          Stanzas that are not registered will not be converted into
          stanza objects, but may still be processed using handlers and
          matchers.
          """
          del self.__root_stanza[stanza_class]
  
      def add_handler(self, mask, pointer, name=None, disposable=False,
                      threaded=False, filter=False, instream=False):
          """
          A shortcut method for registering a handler using XML masks.
  
          Arguments:
              mask       -- An XML snippet matching the structure of the
                            stanzas that will be passed to this handler.
              pointer    -- The handler function itself.
              name       -- A unique name for the handler. A name will
                            be generated if one is not provided.
              disposable -- Indicates if the handler should be discarded
                            after one use.
              threaded   -- Deprecated. Remains for backwards compatibility.
              filter     -- Deprecated. Remains for backwards compatibility.
              instream   -- Indicates if the handler should execute during
                            stream processing and not during normal event
                            processing.
          """
          # To prevent circular dependencies, we must load the matcher
          # and handler classes here.
  
          if name is None:
              name = 'add_handler_%s' % self.getNewId()
          self.registerHandler(XMLCallback(name, MatchXMLMask(mask), pointer,
                                           once=disposable, instream=instream))
  
      def register_handler(self, handler, before=None, after=None):
          """
          Add a stream event handler that will be executed when a matching
          stanza is received.
  
          Arguments:
              handler -- The handler object to execute.
          """
          if handler.stream is None:
              self.__handlers.append(handler)
              handler.stream = weakref.ref(self)
  
      def remove_handler(self, name):
          """
          Remove any stream event handlers with the given name.
  
          Arguments:
              name -- The name of the handler.
          """
          idx = 0
          for handler in self.__handlers:
              if handler.name == name:
                  self.__handlers.pop(idx)
                  return True
              idx += 1
          return False
  
      def get_dns_records(self, domain, port=None):
          """
          Get the DNS records for a domain.
  
          Arguments:
              domain -- The domain in question.
              port   -- If the results don't include a port, use this one.
          """
          if port is None:
              port = self.default_port
          if DNSPYTHON:
              resolver = dns.resolver.get_default_resolver()
              self.configure_dns(resolver, domain=domain, port=port)
  
              try:
                  answers = resolver.query(domain, dns.rdatatype.A)
              except (dns.resolver.NXDOMAIN, dns.resolver.NoAnswer):
                  log.warning("No A records for %s" , domain)
                  return [((domain, port), 0, 0)]
              except dns.exception.Timeout:
                  log.warning("DNS resolution timed out " + \
                              "for A record of %s" % domain)
                  return [((domain, port), 0, 0)]
              else:
                  return [((ans.address, port), 0, 0) for ans in answers]
          else:
              log.warning("dnspython is not installed -- " + \
                          "relying on OS A record resolution")
              self.configure_dns(None, domain=domain, port=port)
              return [((domain, port), 0, 0)]
  
      def pick_dns_answer(self, domain, port=None):
          """
          Pick a server and port from DNS answers.
          Gets DNS answers if none available.
          Removes used answer from available answers.
  
          Arguments:
              domain -- The domain in question.
              port   -- If the results don't include a port, use this one.
          """
          if not self.dns_answers:
              self.dns_answers = self.get_dns_records(domain, port)
          addresses = {}
          intmax = 0
          topprio = 65535
          for answer in self.dns_answers:
              topprio = min(topprio, answer[1])
          for answer in self.dns_answers:
              if answer[1] == topprio:
                  intmax += answer[2]
                  addresses[intmax] = answer[0]
  
          #python3 returns a generator for dictionary keys
          items = [x for x in addresses.keys()]
          items.sort()
  
          picked = random.randint(0, intmax)
          for item in items:
              if picked <= item:
                  address = addresses[item]
                  break
          for idx, answer in enumerate(self.dns_answers):
              if self.dns_answers[0] == address:
                  break
          self.dns_answers.pop(idx)
          log.debug("Trying to connect to %s:%s" , address)
          return address
  
      def add_event_handler(self, name, pointer,
                            threaded=False, disposable=False):
          """
          Add a custom event handler that will be executed whenever
          its event is manually triggered.
  
          Arguments:
              name       -- The name of the event that will trigger
                            this handler.
              pointer    -- The function to execute.
              threaded   -- If set to True, the handler will execute
                            in its own thread. Defaults to False.
              disposable -- If set to True, the handler will be
                            discarded after one use. Defaults to False.
          """
          if not name in self.__event_handlers:
              self.__event_handlers[name] = []
          self.__event_handlers[name].append((pointer, threaded, disposable))
  
      def del_event_handler(self, name, pointer):
          """
          Remove a function as a handler for an event.
  
          Arguments:
              name    -- The name of the event.
              pointer -- The function to remove as a handler.
          """
          if not name in self.__event_handlers:
              return
  
          # Need to keep handlers that do not use
          # the given function pointer
          def filter_pointers(handler):
              return handler[0] != pointer
  
          self.__event_handlers[name] = list(filter(
              filter_pointers,
              self.__event_handlers[name]))
  
      def event_handled(self, name):
          """
          Indicates if an event has any associated handlers.
  
          Returns the number of registered handlers.
  
          Arguments:
              name -- The name of the event to check.
          """
          return len(self.__event_handlers.get(name, []))
  
      def event(self, name, data={}, direct=False):
          """
          Manually trigger a custom event.
  
          Arguments:
              name     -- The name of the event to trigger.
              data     -- Data that will be passed to each event handler.
                          Defaults to an empty dictionary.
              direct   -- Runs the event directly if True, skipping the
                          event queue. All event handlers will run in the
                          same thread.
          """
          handlers = self.__event_handlers.get(name, [])
          for handler in handlers:
              #TODO:  Data should not be copied, but should be read only,
              #       but this might break current code so it's left for future.
  
              out_data = copy.copy(data) if len(handlers) > 1 else data
              old_exception = getattr(data, 'exception', None)
              if direct:
                  try:
                      handler[0](out_data)
                  except Exception as e:
                      error_msg = 'Error processing event handler: %s'
                      log.exception(error_msg , str(handler[0]))
                      if old_exception:
                          old_exception(e)
                      else:
                          self.exception(e)
              else:
                  self.event_queue.put(('event', handler, out_data))
              if handler[2]:
                  # If the handler is disposable, we will go ahead and
                  # remove it now instead of waiting for it to be
                  # processed in the queue.
                  with self.__event_handlers_lock:
                      try:
                          h_index = self.__event_handlers[name].index(handler)
                          self.__event_handlers[name].pop(h_index)
                      except:
                          pass
  
      def schedule(self, name, seconds, callback, args=None,
                   kwargs=None, repeat=False):
          """
          Schedule a callback function to execute after a given delay.
  
          Arguments:
              name     -- A unique name for the scheduled callback.
              seconds  -- The time in seconds to wait before executing.
              callback -- A pointer to the function to execute.
              args     -- A tuple of arguments to pass to the function.
              kwargs   -- A dictionary of keyword arguments to pass to
                          the function.
              repeat   -- Flag indicating if the scheduled event should
                          be reset and repeat after executing.
          """
          self.scheduler.add(name, seconds, callback, args, kwargs,
                             repeat, qpointer=self.event_queue)
  
      def incoming_filter(self, xml):
          """
          Filter incoming XML objects before they are processed.
  
          Possible uses include remapping namespaces, or correcting elements
          from sources with incorrect behavior.
  
          Meant to be overridden.
          """
          return xml
  
      def send(self, data, mask=None, timeout=None, now=False):
          """
          A wrapper for send_raw for sending stanza objects.
  
          May optionally block until an expected response is received.
  
          Arguments:
              data    -- The stanza object to send on the stream.
              mask    -- Deprecated. An XML snippet matching the structure
                         of the expected response. Execution will block
                         in this thread until the response is received
                         or a timeout occurs.
              timeout -- Time in seconds to wait for a response before
                         continuing. Defaults to RESPONSE_TIMEOUT.
              now     -- Indicates if the send queue should be skipped,
                         sending the stanza immediately. Useful mainly
                         for stream initialization stanzas.
                         Defaults to False.
          """
          if timeout is None:
              timeout = self.response_timeout
          if hasattr(mask, 'xml'):
              mask = mask.xml
          data = str(data)
          if mask is not None:
              log.warning("Use of send mask waiters is deprecated.")
              wait_for = Waiter("SendWait_%s" % self.new_id(),
                                MatchXMLMask(mask))
              self.register_handler(wait_for)
          self.send_raw(data, now)
          if mask is not None:
              return wait_for.wait(timeout)
  
      def send_xml(self, data, mask=None, timeout=None, now=False):
          """
          Send an XML object on the stream, and optionally wait
          for a response.
  
          Arguments:
              data    -- The XML object to send on the stream.
              mask    -- Deprecated. An XML snippet matching the structure
                         of the expected response. Execution will block
                         in this thread until the response is received
                         or a timeout occurs.
              timeout -- Time in seconds to wait for a response before
                         continuing. Defaults to RESPONSE_TIMEOUT.
              now     -- Indicates if the send queue should be skipped,
                         sending the stanza immediately. Useful mainly
                         for stream initialization stanzas.
                         Defaults to False.
          """
          if timeout is None:
              timeout = self.response_timeout
          return self.send(tostring(data), mask, timeout, now)
  
      def send_raw(self, data, now=False, reconnect=None):
          """
          Send raw data across the stream.
  
          Arguments:
              data      -- Any string value.
              reconnect -- Indicates if the stream should be
                           restarted if there is an error sending
                           the stanza. Used mainly for testing.
                           Defaults to self.auto_reconnect.
          """
          if now:
              log.debug("SEND (IMMED): %s" , data)
              try:
                  data = data.encode('utf-8')
                  total = len(data)
                  sent = 0
                  count = 0
                  while sent < total and not self.stop.is_set():
                      sent += self.socket.send(data[sent:])
                      count += 1
                  if count > 1:
                      log.debug('SENT: %d chunks' , count)
              except Socket.error as serr:
                  self.event('socket_error', serr)
                  log.warning("Failed to send %s" , data)
                  if reconnect is None:
                      reconnect = self.auto_reconnect
                  self.disconnect(reconnect)
          else:
              self.send_queue.put(data)
          return True
  
      def process(self, **kwargs):
          """
          Initialize the XML streams and begin processing events.
  
          The number of threads used for processing stream events is determined
          by HANDLER_THREADS.
  
          Arguments:
              block -- If block=False then event dispatcher will run
                       in a separate thread, allowing for the stream to be
                       used in the background for another application.
                       Otherwise, process(block=True) blocks the current thread.
                       Defaults to False.
  
              **threaded is deprecated and included for API compatibility**
              threaded -- If threaded=True then event dispatcher will run
                          in a separate thread, allowing for the stream to be
                          used in the background for another application.
                          Defaults to True.
  
              Event handlers and the send queue will be threaded
              regardless of these parameters.
          """
          if 'threaded' in kwargs and 'block' in kwargs:
              raise ValueError("process() called with both " + \
                               "block and threaded arguments")
          elif 'block' in kwargs:
              threaded = not(kwargs.get('block', False))
          else:
              threaded = kwargs.get('threaded', True)
  
          self.scheduler.process(threaded=True)
  
          def start_thread(name, target):
              self.__thread[name] = threading.Thread(name=name, target=target)
              self.__thread[name].daemon = True
              self.__thread[name].start()
  
          for t in range(0, HANDLER_THREADS):
              log.debug("Starting HANDLER THREAD")
              start_thread('stream_event_handler_%s' % t, self._event_runner)
  
          start_thread('send_thread', self._send_thread)
  
          if threaded:
              # Run the XML stream in the background for another application.
              start_thread('process', self._process)
          else:
              self._process()
  
      def _process(self):
          """
          Start processing the XML streams.
  
          Processing will continue after any recoverable errors
          if reconnections are allowed.
          """
  
          # The body of this loop will only execute once per connection.
          # Additional passes will be made only if an error occurs and
          # reconnecting is permitted.
          while True:
              try:
                  # The call to self.__read_xml will block and prevent
                  # the body of the loop from running until a disconnect
                  # occurs. After any reconnection, the stream header will
                  # be resent and processing will resume.
                  while not self.stop.is_set():
                      # Only process the stream while connected to the server
                      if not self.state.ensure('connected', wait=0.1,
                                               block_on_transition=True):
                          continue
                      # Ensure the stream header is sent for any
                      # new connections.
                      if not self.session_started_event.is_set():
                          self.send_raw(self.stream_header, now=True)
                      if not self.__read_xml():
                          # If the server terminated the stream, end processing
                          break
              except SyntaxError as e:
                  log.error("Error reading from XML stream.")
                  self.exception(e)
              except KeyboardInterrupt:
                  log.debug("Keyboard Escape Detected in _process")
                  self.stop.set()
              except SystemExit:
                  log.debug("SystemExit in _process")
                  self.stop.set()
                  self.scheduler.quit()
              except Socket.error as serr:
                  self.event('socket_error', serr)
                  log.exception('Socket Error')
              except:
                  if not self.stop.is_set():
                      log.exception('Connection error.')
  
              if not self.stop.is_set() and self.auto_reconnect:
                  self.reconnect()
              else:
                  self.disconnect()
                  break
  
      def __read_xml(self):
          """
          Parse the incoming XML stream, raising stream events for
          each received stanza.
          """
          depth = 0
          root = None
          for event, xml in ET.iterparse(self.filesocket, (b'end', b'start')):
              if event == b'start':
                  if depth == 0:
                      # We have received the start of the root element.
                      root = xml
                      # Perform any stream initialization actions, such
                      # as handshakes.
                      self.stream_end_event.clear()
                      self.start_stream_handler(root)
                  depth += 1
              if event == b'end':
                  depth -= 1
                  if depth == 0:
                      # The stream's root element has closed,
                      # terminating the stream.
                      log.debug("End of stream recieved")
                      self.stream_end_event.set()
                      return False
                  elif depth == 1:
                      # We only raise events for stanzas that are direct
                      # children of the root element.
                      try:
                          self.__spawn_event(xml)
                      except RestartStream:
                          return True
                      if root is not None:
                          # Keep the root element empty of children to
                          # save on memory use.
                          root.clear()
          log.debug("Ending read XML loop")
  
      def _build_stanza(self, xml, default_ns=None):
          """
          Create a stanza object from a given XML object.
  
          If a specialized stanza type is not found for the XML, then
          a generic StanzaBase stanza will be returned.
  
          Arguments:
              xml        -- The XML object to convert into a stanza object.
              default_ns -- Optional default namespace to use instead of the
                            stream's current default namespace.
          """
          if default_ns is None:
              default_ns = self.default_ns
          stanza_type = StanzaBase
          for stanza_class in self.__root_stanza:
              if xml.tag == "{%s}%s" % (default_ns, stanza_class.name) or \
                 xml.tag == stanza_class.tag_name():
                  stanza_type = stanza_class
                  break
          stanza = stanza_type(self, xml)
          return stanza
  
      def __spawn_event(self, xml):
          """
          Analyze incoming XML stanzas and convert them into stanza
          objects if applicable and queue stream events to be processed
          by matching handlers.
  
          Arguments:
              xml -- The XML stanza to analyze.
          """
          # tostring is very expensive.
          if log.isEnabledFor(logging.DEBUG):
              log.debug("RECV: %s" , tostring(xml,
                                              xmlns=self.default_ns,
                                              stream=self))
          # Apply any preprocessing filters.
          xml = self.incoming_filter(xml)
  
          # Convert the raw XML object into a stanza object. If no registered
          # stanza type applies, a generic StanzaBase stanza will be used.
          stanza = self._build_stanza(xml)
  
          # Match the stanza against registered handlers. Handlers marked
          # to run "in stream" will be executed immediately; the rest will
          # be queued.
          unhandled = True
          matched_handlers = filter(lambda h: h.match(stanza), self.__handlers)
          for handler in matched_handlers:
              stanza_copy = copy.copy(stanza) if len(matched_handlers) > 1 else stanza
              handler.prerun(stanza_copy)
              self.event_queue.put(('stanza', handler, stanza_copy))
              try:
                  if handler.check_delete():
                      self.__handlers.remove(handler)
              except:
                  pass  # not thread safe
              unhandled = False
  
          # Some stanzas require responses, such as Iq queries. A default
          # handler will be executed immediately for this case.
          if unhandled:
              stanza.unhandled()
  
      def _threaded_event_wrapper(self, func, args):
          """
          Capture exceptions for event handlers that run
          in individual threads.
  
          Arguments:
              func -- The event handler to execute.
              args -- Arguments to the event handler.
          """
          # this is always already copied before this is invoked
          orig = args[0]
          try:
              func(*args)
          except Exception as e:
              error_msg = 'Error processing event handler: %s'
              log.exception(error_msg , str(func))
              if hasattr(orig, 'exception'):
                  orig.exception(e)
              else:
                  self.exception(e)
  
      def _event_runner(self):
          """
          Process the event queue and execute handlers.
  
          The number of event runner threads is controlled by HANDLER_THREADS.
  
          Stream event handlers will all execute in this thread. Custom event
          handlers may be spawned in individual threads.
          """
          log.debug("Loading event runner")
          try:
              while not self.stop.isSet():
                  try:
                      wait = self.wait_timeout
                      event = self.event_queue.get(True, timeout=wait)
                  except queue.Empty:
                      event = None
                  if event is None:
                      continue
  
                  etype, handler = event[0:2]
                  args = event[2:]
                  orig = copy.copy(args[0])
  
                  if etype == 'stanza':
                      try:
                          handler.run(args[0])
                      except Exception as e:
                          error_msg = 'Error processing stream handler: %s'
                          log.exception(error_msg , handler.name)
                          orig.exception(e)
                  elif etype == 'schedule':
                      name = args[1]
                      try:
                          log.debug('Scheduled event: %s: %s' , name, args[0])
                          handler(*args[0])
                      except Exception as e:
                          log.exception('Error processing scheduled task')
                          self.exception(e)
                  elif etype == 'event':
                      func, threaded, disposable = handler
                      try:
                          if threaded:
                              x = threading.Thread(
                                      name="Event_%s" % str(func),
                                      target=self._threaded_event_wrapper,
                                      args=(func, args))
                              x.start()
                          else:
                              func(*args)
                      except Exception as e:
                          error_msg = 'Error processing event handler: %s'
                          log.exception(error_msg , str(func))
                          if hasattr(orig, 'exception'):
                              orig.exception(e)
                          else:
                              self.exception(e)
                  elif etype == 'quit':
                      log.debug("Quitting event runner thread")
                      return False
          except KeyboardInterrupt:
              log.debug("Keyboard Escape Detected in _event_runner")
              self.event('killed', direct=True)
              self.disconnect()
              return
          except SystemExit:
              self.disconnect()
              self.event_queue.put(('quit', None, None))
              return
  
      def _send_thread(self):
          """
          Extract stanzas from the send queue and send them on the stream.
          """
          try:
              while not self.stop.is_set():
                  self.session_started_event.wait()
                  if self.__failed_send_stanza is not None:
                      data = self.__failed_send_stanza
                      self.__failed_send_stanza = None
                  else:
                      try:
                          data = self.send_queue.get(True, 1)
                      except queue.Empty:
                          continue
                  log.debug("SEND: %s" , data)
                  try:
                      enc_data = data.encode('utf-8')
                      total = len(enc_data)
                      sent = 0
                      count = 0
                      while sent < total and not self.stop.is_set():
                          sent += self.socket.send(enc_data[sent:])
                          count += 1
                      if count > 1:
                          log.debug('SENT: %d chunks' , count)
                      self.send_queue.task_done()
                  except Socket.error as serr:
                      self.event('socket_error', serr)
                      log.warning("Failed to send %s" , data)
                      self.__failed_send_stanza = data
                      self.disconnect(self.auto_reconnect)
          except Exception as ex:
              log.exception('Unexpected error in send thread: %s' , ex)
              self.exception(ex)
              if not self.stop.is_set():
                  self.disconnect(self.auto_reconnect)
  
      def exception(self, exception):
          """
          Process an unknown exception.
  
          Meant to be overridden.
  
          Arguments:
              exception -- An unhandled exception object.
          """
          pass
  
  
  # To comply with PEP8, method names now use underscores.
  # Deprecated method names are re-mapped for backwards compatibility.
  XMLStream.startTLS = XMLStream.start_tls
  XMLStream.registerStanza = XMLStream.register_stanza
  XMLStream.removeStanza = XMLStream.remove_stanza
  XMLStream.registerHandler = XMLStream.register_handler
  XMLStream.removeHandler = XMLStream.remove_handler
  XMLStream.setSocket = XMLStream.set_socket
  XMLStream.sendRaw = XMLStream.send_raw
  XMLStream.getId = XMLStream.get_id
  XMLStream.getNewId = XMLStream.new_id
  XMLStream.sendXML = XMLStream.send_xml
  