text: '''
  Implementation of a Threaded Modbus Server
  ------------------------------------------
  
  '''
  from binascii import b2a_hex
  import SocketServer
  import serial
  import socket
  import traceback
  
  from pymodbus.constants import Defaults
  from pymodbus.factory import ServerDecoder
  from pymodbus.datastore import ModbusServerContext
  from pymodbus.device import ModbusControlBlock
  from pymodbus.device import ModbusDeviceIdentification
  from pymodbus.transaction import *
  from pymodbus.exceptions import NotImplementedException, NoSuchSlaveException
  from pymodbus.pdu import ModbusExceptions as merror
  
  #---------------------------------------------------------------------------#
  # Logging
  #---------------------------------------------------------------------------#
  import logging
  _logger = logging.getLogger(__name__)
  
  
  #---------------------------------------------------------------------------#
  # Protocol Handlers
  #---------------------------------------------------------------------------#
  class ModbusBaseRequestHandler(SocketServer.BaseRequestHandler):
      ''' Implements the modbus server protocol
  
      This uses the socketserver.BaseRequestHandler to implement
      the client handler.
      '''
  
      def setup(self):
          ''' Callback for when a client connects
          '''
          _logger.debug("Client Connected [%s:%s]" % self.client_address)
          self.running = True
          self.framer = self.server.framer(self.server.decoder)
          self.server.threads.append(self)
  
      def finish(self):
          ''' Callback for when a client disconnects
          '''
          _logger.debug("Client Disconnected [%s:%s]" % self.client_address)
          self.server.threads.remove(self)
  
      def execute(self, request):
          ''' The callback to call with the resulting message
  
          :param request: The decoded request message
          '''
          try:
              context = self.server.context[request.unit_id]
              response = request.execute(context)
          except NoSuchSlaveException, ex:
              _logger.debug("requested slave does not exist: %s; %s", ex, traceback.format_exc() )
              if self.server.ignore_missing_slaves:
                  return # the client will simply timeout waiting for a response
              response = request.doException(merror.GatewayNoResponse)
          except Exception, ex:
              _logger.debug("Datastore unable to fulfill request: %s; %s", ex, traceback.format_exc() )
              response = request.doException(merror.SlaveFailure)
          response.transaction_id = request.transaction_id
          response.unit_id = request.unit_id
          self.send(response)
  
      #---------------------------------------------------------------------------#
      # Base class implementations
      #---------------------------------------------------------------------------#
      def handle(self):
          ''' Callback when we receive any data
          '''
          raise NotImplementedException("Method not implemented by derived class")
  
      def send(self, message):
          ''' Send a request (string) to the network
  
          :param message: The unencoded modbus response
          '''
          raise NotImplementedException("Method not implemented by derived class")
  
  
  class ModbusSingleRequestHandler(ModbusBaseRequestHandler):
      ''' Implements the modbus server protocol
  
      This uses the socketserver.BaseRequestHandler to implement
      the client handler for a single client(serial clients)
      '''
  
      def handle(self):
          ''' Callback when we receive any data
          '''
          while self.running:
              try:
                  data = self.request.recv(1024)
                  if data:
                      if _logger.isEnabledFor(logging.DEBUG):
                          _logger.debug(" ".join([hex(ord(x)) for x in data]))
                      self.framer.processIncomingPacket(data, self.execute)
              except Exception, msg:
                  # since we only have a single socket, we cannot exit
                  _logger.error("Socket error occurred %s" % msg)
  
      def send(self, message):
          ''' Send a request (string) to the network
  
          :param message: The unencoded modbus response
          '''
          if message.should_respond:
              #self.server.control.Counter.BusMessage += 1
              pdu = self.framer.buildPacket(message)
              if _logger.isEnabledFor(logging.DEBUG):
                  _logger.debug('send: %s' % b2a_hex(pdu))
              return self.request.send(pdu)
  
  
  class ModbusConnectedRequestHandler(ModbusBaseRequestHandler):
      ''' Implements the modbus server protocol
  
      This uses the socketserver.BaseRequestHandler to implement
      the client handler for a connected protocol (TCP).
      '''
  
      def handle(self):
          '''Callback when we receive any data, until self.running becomes not True.  Blocks indefinitely
          awaiting data.  If shutdown is required, then the global socket.settimeout(<seconds>) may be
          used, to allow timely checking of self.running.  However, since this also affects socket
          connects, if there are outgoing socket connections used in the same program, then these will
          be prevented, if the specfied timeout is too short.  Hence, this is unreliable.
  
          To respond to Modbus...Server.server_close() (which clears each handler's self.running),
          derive from this class to provide an alternative handler that awakens from time to time when
          no input is available and checks self.running.  Use Modbus...Server( handler=... ) keyword
          to supply the alternative request handler class.
  
          '''
          while self.running:
              try:
                  data = self.request.recv(1024)
                  if not data: self.running = False
                  if _logger.isEnabledFor(logging.DEBUG):
                      _logger.debug(" ".join([hex(ord(x)) for x in data]))
                  # if not self.server.control.ListenOnly:
                  self.framer.processIncomingPacket(data, self.execute)
              except socket.timeout as msg:
                  if _logger.isEnabledFor(logging.DEBUG):
                      _logger.debug("Socket timeout occurred %s", msg)
                  pass
              except socket.error as msg:
                  _logger.error("Socket error occurred %s", msg)
                  self.running = False
              except:
                  _logger.error("Socket exception occurred %s", traceback.format_exc() )
                  self.running = False
  
      def send(self, message):
          ''' Send a request (string) to the network
  
          :param message: The unencoded modbus response
          '''
          if message.should_respond:
              #self.server.control.Counter.BusMessage += 1
              pdu = self.framer.buildPacket(message)
              if _logger.isEnabledFor(logging.DEBUG):
                  _logger.debug('send: %s' % b2a_hex(pdu))
              return self.request.send(pdu)
  
  
  class ModbusDisconnectedRequestHandler(ModbusBaseRequestHandler):
      ''' Implements the modbus server protocol
  
      This uses the socketserver.BaseRequestHandler to implement
      the client handler for a disconnected protocol (UDP). The
      only difference is that we have to specify who to send the
      resulting packet data to.
      '''
  
      def handle(self):
          ''' Callback when we receive any data
          '''
          while self.running:
              try:
                  data, self.request = self.request
                  if not data: self.running = False
                  if _logger.isEnabledFor(logging.DEBUG):
                      _logger.debug(" ".join([hex(ord(x)) for x in data]))
                  # if not self.server.control.ListenOnly:
                  self.framer.processIncomingPacket(data, self.execute)
              except socket.timeout: pass
              except socket.error, msg:
                  _logger.error("Socket error occurred %s" % msg)
                  self.running = False
              except: self.running = False
  
      def send(self, message):
          ''' Send a request (string) to the network
  
          :param message: The unencoded modbus response
          '''
          if message.should_respond:
              #self.server.control.Counter.BusMessage += 1
              pdu = self.framer.buildPacket(message)
              if _logger.isEnabledFor(logging.DEBUG):
                  _logger.debug('send: %s' % b2a_hex(pdu))
              return self.request.sendto(pdu, self.client_address)
  
  
  #---------------------------------------------------------------------------#
  # Server Implementations
  #---------------------------------------------------------------------------#
  class ModbusTcpServer(SocketServer.ThreadingTCPServer):
      '''
      A modbus threaded tcp socket server
  
      We inherit and overload the socket server so that we
      can control the client threads as well as have a single
      server context instance.
      '''
  
      def __init__(self, context, framer=None, identity=None, address=None, handler=None, **kwargs):
          ''' Overloaded initializer for the socket server
  
          If the identify structure is not passed in, the ModbusControlBlock
          uses its own empty structure.
  
          :param context: The ModbusServerContext datastore
          :param framer: The framer strategy to use
          :param identity: An optional identify structure
          :param address: An optional (interface, port) to bind to.
          :param handler: A handler for each client session; default is ModbusConnectedRequestHandler
          :param ignore_missing_slaves: True to not send errors on a request to a missing slave
          '''
          self.threads = []
          self.decoder = ServerDecoder()
          self.framer  = framer  or ModbusSocketFramer
          self.context = context or ModbusServerContext()
          self.control = ModbusControlBlock()
          self.address = address or ("", Defaults.Port)
          self.ignore_missing_slaves = kwargs.get('ignore_missing_slaves', Defaults.IgnoreMissingSlaves)
  
          if isinstance(identity, ModbusDeviceIdentification):
              self.control.Identity.update(identity)
  
          SocketServer.ThreadingTCPServer.__init__(self,
              self.address, handler or ModbusConnectedRequestHandler)
  
      def process_request(self, request, client):
          ''' Callback for connecting a new client thread
  
          :param request: The request to handle
          :param client: The address of the client
          '''
          _logger.debug("Started thread to serve client at " + str(client))
          SocketServer.ThreadingTCPServer.process_request(self, request, client)
  
      def server_close(self):
          ''' Callback for stopping the running server
          '''
          _logger.debug("Modbus server stopped")
          self.socket.close()
          for thread in self.threads:
              thread.running = False
  
  
  class ModbusUdpServer(SocketServer.ThreadingUDPServer):
      '''
      A modbus threaded udp socket server
  
      We inherit and overload the socket server so that we
      can control the client threads as well as have a single
      server context instance.
      '''
  
      def __init__(self, context, framer=None, identity=None, address=None, handler=None, **kwargs):
          ''' Overloaded initializer for the socket server
  
          If the identify structure is not passed in, the ModbusControlBlock
          uses its own empty structure.
  
          :param context: The ModbusServerContext datastore
          :param framer: The framer strategy to use
          :param identity: An optional identify structure
          :param address: An optional (interface, port) to bind to.
          :param handler: A handler for each client session; default is ModbusDisonnectedRequestHandler
          :param ignore_missing_slaves: True to not send errors on a request to a missing slave
          '''
          self.threads = []
          self.decoder = ServerDecoder()
          self.framer  = framer  or ModbusSocketFramer
          self.context = context or ModbusServerContext()
          self.control = ModbusControlBlock()
          self.address = address or ("", Defaults.Port)
          self.ignore_missing_slaves = kwargs.get('ignore_missing_slaves', Defaults.IgnoreMissingSlaves)
  
          if isinstance(identity, ModbusDeviceIdentification):
              self.control.Identity.update(identity)
  
          SocketServer.ThreadingUDPServer.__init__(self,
              self.address, handler or ModbusDisconnectedRequestHandler)
  
      def process_request(self, request, client):
          ''' Callback for connecting a new client thread
  
          :param request: The request to handle
          :param client: The address of the client
          '''
          packet, socket = request # TODO I might have to rewrite
          _logger.debug("Started thread to serve client at " + str(client))
          SocketServer.ThreadingUDPServer.process_request(self, request, client)
  
      def server_close(self):
          ''' Callback for stopping the running server
          '''
          _logger.debug("Modbus server stopped")
          self.socket.close()
          for thread in self.threads:
              thread.running = False
  
  
  class ModbusSerialServer(object):
      '''
      A modbus threaded udp socket server
  
      We inherit and overload the socket server so that we
      can control the client threads as well as have a single
      server context instance.
      '''
  
      def __init__(self, context, framer=None, identity=None, **kwargs):
          ''' Overloaded initializer for the socket server
  
          If the identify structure is not passed in, the ModbusControlBlock
          uses its own empty structure.
  
          :param context: The ModbusServerContext datastore
          :param framer: The framer strategy to use
          :param identity: An optional identify structure
          :param port: The serial port to attach to
          :param stopbits: The number of stop bits to use
          :param bytesize: The bytesize of the serial messages
          :param parity: Which kind of parity to use
          :param baudrate: The baud rate to use for the serial device
          :param timeout: The timeout to use for the serial device
          :param ignore_missing_slaves: True to not send errors on a request to a missing slave
          '''
          self.threads = []
          self.decoder = ServerDecoder()
          self.framer  = framer  or ModbusAsciiFramer
          self.context = context or ModbusServerContext()
          self.control = ModbusControlBlock()
  
          if isinstance(identity, ModbusDeviceIdentification):
              self.control.Identity.update(identity)
  
          self.device   = kwargs.get('port', 0)
          self.stopbits = kwargs.get('stopbits', Defaults.Stopbits)
          self.bytesize = kwargs.get('bytesize', Defaults.Bytesize)
          self.parity   = kwargs.get('parity',   Defaults.Parity)
          self.baudrate = kwargs.get('baudrate', Defaults.Baudrate)
          self.timeout  = kwargs.get('timeout',  Defaults.Timeout)
          self.ignore_missing_slaves = kwargs.get('ignore_missing_slaves', Defaults.IgnoreMissingSlaves)
          self.socket   = None
          self._connect()
          self.is_running = True
  
      def _connect(self):
          ''' Connect to the serial server
  
          :returns: True if connection succeeded, False otherwise
          '''
          if self.socket: return True
          try:
              self.socket = serial.Serial(port=self.device, timeout=self.timeout,
                  bytesize=self.bytesize, stopbits=self.stopbits,
                  baudrate=self.baudrate, parity=self.parity)
          except serial.SerialException, msg:
              _logger.error(msg)
          return self.socket != None
  
      def _build_handler(self):
          ''' A helper method to create and monkeypatch
              a serial handler.
  
          :returns: A patched handler
          '''
          request = self.socket
          request.send = request.write
          request.recv = request.read
          handler = ModbusSingleRequestHandler(request,
              (self.device, self.device), self)
          return handler
  
      def serve_forever(self):
          ''' Callback for connecting a new client thread
  
          :param request: The request to handle
          :param client: The address of the client
          '''
          _logger.debug("Started thread to serve client")
          handler = self._build_handler()
          while self.is_running:
              handler.handle()
  
      def server_close(self):
          ''' Callback for stopping the running server
          '''
          _logger.debug("Modbus server stopped")
          self.is_running = False
          self.socket.close()
  
  
  #---------------------------------------------------------------------------#
  # Creation Factories
  #---------------------------------------------------------------------------#
  def StartTcpServer(context=None, identity=None, address=None, **kwargs):
      ''' A factory to start and run a tcp modbus server
  
      :param context: The ModbusServerContext datastore
      :param identity: An optional identify structure
      :param address: An optional (interface, port) to bind to.
      :param ignore_missing_slaves: True to not send errors on a request to a missing slave
      '''
      framer = ModbusSocketFramer
      server = ModbusTcpServer(context, framer, identity, address, **kwargs)
      server.serve_forever()
  
  
  def StartUdpServer(context=None, identity=None, address=None, **kwargs):
      ''' A factory to start and run a udp modbus server
  
      :param context: The ModbusServerContext datastore
      :param identity: An optional identify structure
      :param address: An optional (interface, port) to bind to.
      :param framer: The framer to operate with (default ModbusSocketFramer)
      :param ignore_missing_slaves: True to not send errors on a request to a missing slave
      '''
      framer = kwargs.pop('framer', ModbusSocketFramer)
      server = ModbusUdpServer(context, framer, identity, address, **kwargs)
      server.serve_forever()
  
  
  def StartSerialServer(context=None, identity=None, **kwargs):
      ''' A factory to start and run a udp modbus server
  
      :param context: The ModbusServerContext datastore
      :param identity: An optional identify structure
      :param framer: The framer to operate with (default ModbusAsciiFramer)
      :param port: The serial port to attach to
      :param stopbits: The number of stop bits to use
      :param bytesize: The bytesize of the serial messages
      :param parity: Which kind of parity to use
      :param baudrate: The baud rate to use for the serial device
      :param timeout: The timeout to use for the serial device
      :param ignore_missing_slaves: True to not send errors on a request to a missing slave
      '''
      framer = kwargs.pop('framer', ModbusAsciiFramer)
      server = ModbusSerialServer(context, framer, identity, **kwargs)
      server.serve_forever()
  
  #---------------------------------------------------------------------------#
  # Exported symbols
  #---------------------------------------------------------------------------#
  __all__ = [
      "StartTcpServer", "StartUdpServer", "StartSerialServer"
  ]
  