#322 reuse address

[dhoomakethu]

Allows reusing the address when running pymodbus synchronous server. A new keyword arg is introduced allow_reuse_address (set to false by default to be backward compatible) to control this feature.

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, allow_reuse_address=False,
                 **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 allow_reuse_address: Whether the server will allow the
                        reuse of an address.
        :param ignore_missing_slaves: True to not send errors on a request
                                        to a missing slave
        """