socket_protocol/__init__.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
"""
socket_protocol (Socket Protocol)
=================================

**Author:**

* Dirk Alders <sudo-dirk@mount-mockery.de>

**Description:**

    This Module supports point to point communication for client-server issues.

**Submodules:**

* :class:`socket_protocol.data_storage`
* :class:`socket_protocol.pure_json_protocol`
* :class:`socket_protocol.struct_json_protocol`

**Unittest:**

        See also the :download:`unittest <socket_protocol/_testresults_/unittest.pdf>` documentation.

**Module Documentation:**

"""
__DEPENDENCIES__ = ['stringtools']

import stringtools

import binascii
import hashlib
import json
import logging
import os
import struct
import sys
import time


try:
    from config import APP_NAME as ROOT_LOGGER_NAME
except ImportError:
    ROOT_LOGGER_NAME = 'root'
logger = logging.getLogger(ROOT_LOGGER_NAME).getChild(__name__)


__DESCRIPTION__ = """The Module {\\tt %s} is designed for point to point communication for client-server issues.
For more Information read the sphinx documentation.""" % __name__.replace('_', '\_')
"""The Module Description"""
__INTERPRETER__ = (2, 3)
"""The Tested Interpreter-Versions"""

SID_AUTH_REQUEST = 0
"""SID for authentification request"""
SID_AUTH_RESPONSE = 1
"""SID for authentification response"""
DID_AUTH_SEED = 0
"""DID for authentification (seed)"""
DID_AUTH_KEY = 1
"""DID for authentification (key)"""
SID_CHANNEL_NAME_REQUEST = 8
"""SID for channel name exchange request """
SID_CHANNEL_NAME_RESPONSE = 9
"""SID for channel name exchange response"""
DID_CHANNEL_NAME = 0
"""DID for channel name """
SID_READ_REQUEST = 10
"""SID for a read data request"""
SID_READ_RESPONSE = 11
"""SID for read data response"""
SID_WRITE_REQUEST = 20
"""SID for a write data request"""
SID_WRITE_RESPONSE = 21
"""SID for a write data response"""
SID_EXECUTE_REQUEST = 30
"""SID for a execute request"""
SID_EXECUTE_RESPONSE = 31
"""SID for a execute response"""

STATUS_OKAY = 0
"""Status for 'okay'"""
STATUS_BUFFERING_UNHANDLED_REQUEST = 1
"""Status for 'unhandled request'"""
STATUS_CALLBACK_ERROR = 2
"""Status for 'callback errors'"""
STATUS_AUTH_REQUIRED = 3
"""Status for 'authentification is required'"""
STATUS_SERVICE_OR_DATA_UNKNOWN = 4
"""Status for 'service or data unknown'"""
STATUS_CHECKSUM_ERROR = 5
"""Status for 'checksum error'"""
STATUS_OPERATION_NOT_PERMITTED = 6
"""Status for 'operation not permitted'"""
STATUS_LOG_LVL = {
    STATUS_OKAY: logging.INFO,
    STATUS_BUFFERING_UNHANDLED_REQUEST: logging.WARNING,
    STATUS_CALLBACK_ERROR: logging.ERROR,
    STATUS_AUTH_REQUIRED: logging.WARNING,
    STATUS_SERVICE_OR_DATA_UNKNOWN: logging.ERROR,
    STATUS_CHECKSUM_ERROR: logging.ERROR,
    STATUS_OPERATION_NOT_PERMITTED: logging.WARNING,
}
"""Status depending log level for messages"""

AUTH_STATE_UNTRUSTED_CONNECTION = 0
"""Authentification Status for an 'Untrusted Connection'"""
AUTH_STATE_SEED_REQUESTED = 1
"""Authentification Status for 'Seed was requested'"""
AUTH_STATE_SEED_TRANSFERRED = 2
"""Authentification Status for 'Seed has been sent'"""
AUTH_STATE_KEY_TRANSFERRED = 3
"""Authentification Status for 'Key has been sent'"""
AUTH_STATE_TRUSTED_CONNECTION = 4
"""Authentification Status for a 'Trusted Connection'"""
AUTH_STATE__NAMES = {AUTH_STATE_UNTRUSTED_CONNECTION: 'Untrusted Connection',
                     AUTH_STATE_SEED_REQUESTED: 'Seed was requested',
                     AUTH_STATE_SEED_TRANSFERRED: 'Seed has been sent',
                     AUTH_STATE_KEY_TRANSFERRED: 'Key has been sent',
                     AUTH_STATE_TRUSTED_CONNECTION: 'Trusted Connection'}
"""Authentification Status names for previous defined authentification states"""


class RequestSidExistsError(Exception):
    pass


class ResponseSidExistsError(Exception):
    pass


class _callback_storage(dict):
    DEFAULT_CHANNEL_NAME = 'all_others'

    def __init__(self, channel_name, log_prefix):
        self.init_channel_name(channel_name)
        self.__log_prefix__ = log_prefix
        dict.__init__(self)

    def init_channel_name(self, channel_name):
        if channel_name is None:
            self.logger = logging.getLogger(ROOT_LOGGER_NAME).getChild(__name__ + '.' + self.DEFAULT_CHANNEL_NAME)
        else:
            self.logger = logging.getLogger(ROOT_LOGGER_NAME).getChild(__name__ + '.' + channel_name)

    def get(self, service_id, data_id):
        if dict.get(self, service_id, {}).get(data_id, None) is not None:
            return self[service_id][data_id]
        elif dict.get(self, service_id, {}).get(None, None) is not None:
            return self[service_id][None]
        elif dict.get(self, None, {}).get(data_id, None) is not None:
            return self[None][data_id]
        elif dict.get(self, None, {}).get(None, None) is not None:
            return self[None][None]
        else:
            return (None, None, None)

    def add(self, service_id, data_id, callback, *args, **kwargs):
        cb_data = self.get(service_id, data_id)
        if dict.get(self, service_id, {}).get(data_id, None) is not None:
            if callback is None:
                self.logger.warning("%s Deleting existing callback %s for service_id (%s) and data_id (%s)!", self.__log_prefix__(), repr(cb_data[0].__name__), repr(service_id), repr(data_id))
                del(self[service_id][data_id])
                return
            else:
                self.logger.warning("%s Overwriting existing callback %s for service_id (%s) and data_id (%s) to %s!", self.__log_prefix__(), repr(cb_data[0].__name__), repr(service_id), repr(data_id), repr(callback.__name__))
        else:
            self.logger.debug("%s Adding callback %s for SID=%s and DID=%s", self.__log_prefix__(), repr(callback.__name__), repr(service_id), repr(data_id))
        if service_id not in self:
            self[service_id] = {}
        self[service_id][data_id] = (callback, args, kwargs)


class data_storage(dict):
    """
    This is a storage object for socket_protocol messages.

    :param status: The message status.
    :type status: int
    :param service_id: The Service-ID.
    :type service_id: int
    :param data_id: The Data-ID.
    :type data_id: int
    :param data: The transfered data.
    :type data: any
    """

    KEY_STATUS = 'status'
    KEY_SERVICE_ID = 'service_id'
    KEY_DATA_ID = 'data_id'
    KEY_DATA = 'data'
    ALL_KEYS = [KEY_DATA, KEY_DATA_ID, KEY_SERVICE_ID, KEY_STATUS]

    def __init__(self, *args, **kwargs):
        dict.__init__(self, *args, **kwargs)
        for key in self.ALL_KEYS:
            if key not in self:
                self[key] = None

    def get_status(self, default=None):
        """
        This Method returns the message status.

        :param default: The default value, if no data is available.
        """
        return self.get(self.KEY_STATUS, default)

    def get_service_id(self, default=None):
        """
        This Method returns the message Service-ID.

        :param default: The default value, if no data is available.
        """
        return self.get(self.KEY_SERVICE_ID, default)

    def get_data_id(self, default=None):
        """
        This Method returns the message Data-ID.

        :param default: The default value, if no data is available.
        """
        return self.get(self.KEY_DATA_ID, default)

    def get_data(self, default=None):
        """
        This Method returns the message data.

        :param default: The default value, if no data is available.
        """
        return self.get(self.KEY_DATA, default)


class pure_json_protocol(object):
    """
    This `class` supports to transfer a message and it's data.

    :param comm_instance: A communication instance.
    :type comm_instance: instance
    :param secret: An optinal secret (e.g. created by ``binascii.hexlify(os.urandom(24))``).
    :type secret: str
    :param auto_auth: An optional parameter to enable (True) automatic authentification, otherwise you need to do it manually, if needed.
    :type auto_auth: bool
    :param channel_name: An optional parameter to set a channel name for logging of the communication.
    :type channel_name: str

    .. hint::

        * The Service-ID is designed to identify the type of the communication (e.g. :const:`READ_REQUEST`, :const:`WRITE_REQUEST`, :const:`READ_RESPONSE`, :const:`WRITE_RESPONSE`, ...)
        * The Data-ID is designed to identify the requests / responses using the same Service_ID.

    .. note:: The :class:`comm_instance` needs to have at least the following interface:

        * A Method :func:`comm_instance.init_channel_name` to set the channel name.
        * A Constant :const:`comm_instance.IS_CLIENT` to identify that the :class:`comm_instance` is a client (True) or a server (False).
        * A Method :func:`comm_instance.is_connected` to identify if the instance is connected (True) or not (False).
        * A Method :func:`comm_instance.reconnect` to initiate a reconnect.
        * A Method :func:`comm_instance.register_callback` to register a data available callback.
        * A Method :func:`comm_instance.register_connect_callback` to register a connect callback.
        * A Method :func:`comm_instance.register_disconnect_callback` to register a disconnect callback.
        * A Method :func:`comm_instance.send` to send data via the :class:`comm_instance`.

    .. note::  The parameter :const:`auto_auth` is only relevant, if a secret is given and the :class:`comm_instance` is a client. The authentification is initiated directly after the connection is established.

    .. note::  The :const:`channel_name`-exchange will be initiated by the client directly after the the connection is established.

        * If a channel_name is given at both communication sides and they are different, the client name is taken over and the server will log a warning message.
    """
    DEFAULT_CHANNEL_NAME = 'all_others'

    def __init__(self, comm_instance, secret=None, auto_auth=False, channel_name=None):
        self.__comm_inst__ = comm_instance
        self.__secret__ = secret
        self.__auto_auth__ = auto_auth
        #
        self.__auth_whitelist__ = {}
        self.__sid_response_dict__ = {}
        self.__sid_name_dict__ = {}
        self.__did_name_dict__ = {}
        #
        self.__status_name_dict = {}
        self.add_status(STATUS_OKAY, 'okay')
        self.add_status(STATUS_BUFFERING_UNHANDLED_REQUEST, 'no callback for service, data buffered')
        self.add_status(STATUS_CALLBACK_ERROR, 'callback error')
        self.add_status(STATUS_AUTH_REQUIRED, 'authentification required')
        self.add_status(STATUS_SERVICE_OR_DATA_UNKNOWN, 'service or data unknown')
        self.add_status(STATUS_CHECKSUM_ERROR, 'checksum error')
        self.add_status(STATUS_OPERATION_NOT_PERMITTED, 'operation not permitted')
        #
        self.__callbacks__ = _callback_storage(channel_name, self.__log_prefix__)
        self.__init_channel_name__(channel_name)
        #
        self.__clean_receive_buffer__()

        self.add_service(SID_AUTH_REQUEST, SID_AUTH_RESPONSE, 'authentification request', 'authentification response')
        self.add_data((SID_AUTH_REQUEST, SID_AUTH_RESPONSE), DID_AUTH_SEED, 'seed')
        self.add_data(SID_AUTH_REQUEST, DID_AUTH_KEY, 'key')
        self.add_data(SID_AUTH_RESPONSE, DID_AUTH_KEY, 'key')
        self.add_msg_to_auth_whitelist_(SID_AUTH_REQUEST, DID_AUTH_SEED)
        self.add_msg_to_auth_whitelist_(SID_AUTH_RESPONSE, DID_AUTH_SEED)
        self.add_msg_to_auth_whitelist_(SID_AUTH_REQUEST, DID_AUTH_KEY)
        self.add_msg_to_auth_whitelist_(SID_AUTH_RESPONSE, DID_AUTH_KEY)
        self.__callbacks__.add(SID_AUTH_REQUEST, DID_AUTH_SEED, self.__authentificate_create_seed__)
        self.__callbacks__.add(SID_AUTH_RESPONSE, DID_AUTH_SEED, self.__authentificate_create_key__)
        self.__callbacks__.add(SID_AUTH_REQUEST, DID_AUTH_KEY, self.__authentificate_check_key__)
        self.__callbacks__.add(SID_AUTH_RESPONSE, DID_AUTH_KEY, self.__authentificate_process_feedback__)
        self.__authentification_state_reset__()

        self.add_service(SID_CHANNEL_NAME_REQUEST, SID_CHANNEL_NAME_RESPONSE, 'channel name request', 'channel name response')
        self.add_data((SID_CHANNEL_NAME_REQUEST, SID_CHANNEL_NAME_RESPONSE), DID_CHANNEL_NAME, 'name')
        self.add_msg_to_auth_whitelist_(SID_CHANNEL_NAME_REQUEST, DID_CHANNEL_NAME)
        self.add_msg_to_auth_whitelist_(SID_CHANNEL_NAME_RESPONSE, DID_CHANNEL_NAME)
        self.__callbacks__.add(SID_CHANNEL_NAME_REQUEST, DID_CHANNEL_NAME, self.__channel_name_request__)
        self.__callbacks__.add(SID_CHANNEL_NAME_RESPONSE, DID_CHANNEL_NAME, self.__channel_name_response__)

        self.add_service(SID_READ_REQUEST, SID_READ_RESPONSE, 'read data request', 'read data response')
        self.add_service(SID_WRITE_REQUEST, SID_WRITE_RESPONSE, 'write data request', 'write data response')
        self.add_service(SID_EXECUTE_REQUEST, SID_EXECUTE_RESPONSE, 'execute request', 'execute response')

        self.__seed__ = None
        self.__comm_inst__.register_callback(self.__data_available_callback__)
        self.__comm_inst__.register_connect_callback(self.__connection_established__)
        self.__comm_inst__.register_disconnect_callback(self.__authentification_state_reset__)
        logger.info('%s Initialisation finished.', self.__log_prefix__())

    def __analyse_frame__(self, frame):
        if sys.version_info >= (3, 0):
            return data_storage(json.loads(frame[:-4].decode('utf-8')))
        else:
            return data_storage(json.loads(frame[:-4]))

    def __authentificate_check_key__(self, msg):
        key = msg.get_data()
        if key == self.__authentificate_salt_and_hash__(self.__seed__):
            self.__authentification_state__ = AUTH_STATE_TRUSTED_CONNECTION
            return STATUS_OKAY, True
        else:
            self.__authentification_state__ = AUTH_STATE_UNTRUSTED_CONNECTION
            return STATUS_OKAY, False

    def __authentificate_create_key__(self, msg):
        self.__authentification_state__ = AUTH_STATE_KEY_TRANSFERRED
        seed = msg.get_data()
        key = self.__authentificate_salt_and_hash__(seed)
        self.send(SID_AUTH_REQUEST, DID_AUTH_KEY, key)

    def __authentificate_create_seed__(self, msg):
        self.__authentification_state__ = AUTH_STATE_SEED_TRANSFERRED
        if sys.version_info >= (3, 0):
            self.__seed__ = binascii.hexlify(os.urandom(32)).decode('utf-8')
        else:
            self.__seed__ = binascii.hexlify(os.urandom(32))
        return STATUS_OKAY, self.__seed__

    def __authentificate_process_feedback__(self, msg):
        feedback = msg.get_data()
        if feedback:
            self.__authentification_state__ = AUTH_STATE_TRUSTED_CONNECTION
            self.logger.info("%s Got positive authentification feedback", self.__log_prefix__())
        else:
            self.__authentification_state__ = AUTH_STATE_UNTRUSTED_CONNECTION
            self.logger.warning("%s Got negative authentification feedback", self.__log_prefix__())
        return STATUS_OKAY, None

    def __authentificate_salt_and_hash__(self, seed):
        if sys.version_info >= (3, 0):
            return hashlib.sha512(bytes(seed, 'utf-8') + self.__secret__).hexdigest()
        else:
            return hashlib.sha512(seed.encode('utf-8') + self.__secret__.encode('utf-8')).hexdigest()

    def __authentification_state_reset__(self):
        self.logger.info("%s Resetting authentification state to AUTH_STATE_UNTRUSTED_CONNECTION", self.__log_prefix__())
        self.__authentification_state__ = AUTH_STATE_UNTRUSTED_CONNECTION

    def __authentification_required__(self, service_id, data_id):
        return data_id not in self.__auth_whitelist__.get(service_id, [])

    def __buffer_received_data__(self, msg):
        if not msg.get_service_id() in self.__msg_buffer__:
            self.__msg_buffer__[msg.get_service_id()] = {}
        if not msg.get_data_id() in self.__msg_buffer__[msg.get_service_id()]:
            self.__msg_buffer__[msg.get_service_id()][msg.get_data_id()] = []
        self.__msg_buffer__[msg.get_service_id()][msg.get_data_id()].append(msg)
        self.logger.debug("%s Message data is stored in buffer and is now ready to be retrieved by receive method", self.__log_prefix__())

    def __build_frame__(self, msg):
        data_frame = json.dumps(self.__mk_msg__(msg.get_status(), msg.get_service_id(), msg.get_data_id(), msg.get_data()))
        if sys.version_info >= (3, 0):
            data_frame = bytes(data_frame, 'utf-8')
        checksum = self.__calc_chksum__(data_frame)
        return data_frame + checksum

    def __calc_chksum__(self, raw_data):
        return struct.pack('>I', binascii.crc32(raw_data) & 0xffffffff)

    @property
    def __channel_name__(self):
        cn = self.logger.name.split('.')[-1]
        if cn != self.DEFAULT_CHANNEL_NAME:
            return cn

    def __channel_name_response__(self, msg):
        data = msg.get_data()
        if self.__channel_name__ is None and data is not None:
            self.__init_channel_name__(data)
            self.logger.info('%s channel name is now %s', self.__log_prefix__(), repr(self.__channel_name__))
        return STATUS_OKAY, None

    def __channel_name_request__(self, msg):
        data = msg.get_data()
        if data is None:
            return STATUS_OKAY, self.__channel_name__
        else:
            prev_channel_name = self.__channel_name__
            self.__init_channel_name__(data)
            if prev_channel_name is not None and prev_channel_name != data:
                self.logger.warning('%s overwriting user defined channel name from %s to %s', self.__log_prefix__(), repr(prev_channel_name), repr(data))
            elif prev_channel_name is None:
                self.logger.info('%s channel name is now %s', self.__log_prefix__(), repr(self.__channel_name__))
            return STATUS_OKAY, None

    def __check_frame_checksum__(self, frame):
        return self.__calc_chksum__(frame[:-4]) == frame[-4:]

    def __clean_receive_buffer__(self):
        self.logger.debug("%s Cleaning up receive-buffer", self.__log_prefix__())
        self.__msg_buffer__ = {}

    def __connection_established__(self):
        self.__clean_receive_buffer__()
        if self.__comm_inst__.IS_CLIENT:
            self.send(SID_CHANNEL_NAME_REQUEST, 0, self.__channel_name__)
        if self.__auto_auth__ and self.__comm_inst__.IS_CLIENT and self.__secret__ is not None:
            self.authentificate()

    def __log_msg__(self, msg, rx_tx_prefix):
        self.logger.log(
            self.__status_log_lvl__(msg.get_status()),
            '%s %s %s, %s, data: "%s"',
            self.__log_prefix__(),
            rx_tx_prefix,
            self.__get_message_name__(msg.get_service_id(), msg.get_data_id()),
            self.__get_status_name__(msg.get_status()),
            repr(msg.get_data())
        )

    def __data_available_callback__(self, comm_inst):
        frame = comm_inst.receive()
        msg = self.__analyse_frame__(frame)
        if not self.__check_frame_checksum__(frame):
            # Wrong Checksum
            self.logger.log(self.__status_log_lvl__(STATUS_CHECKSUM_ERROR), "%s Received message has an invalid checksum. Message will be ignored.", self.__log_prefix__())
            return  # No response needed
        elif not self.check_authentification_state() and self.__authentification_required__(msg.get_service_id(), msg.get_data_id()):
            # Authentification required
            self.__log_msg__(msg, 'RX <-')
            if msg.get_service_id() in self.__sid_response_dict__.keys():
                self.logger.log(self.__status_log_lvl__(STATUS_AUTH_REQUIRED), "%s Authentification is required. Just sending negative response.", self.__log_prefix__())
                status = STATUS_AUTH_REQUIRED
                data = None
            else:
                self.logger.log(self.__status_log_lvl__(STATUS_AUTH_REQUIRED), "%s Authentification is required. Incomming message will be ignored.", self.__log_prefix__())
                return  # No response needed
        else:
            # Valid message
            self.__log_msg__(msg, 'RX <-')
            callback, args, kwargs = self.__callbacks__.get(msg.get_service_id(), msg.get_data_id())
            if msg.get_service_id() in self.__sid_response_dict__.keys():
                #
                # REQUEST RECEIVED
                #
                if callback is None:
                    self.logger.warning("%s Incomming message with no registered callback. Sending negative response.", self.__log_prefix__())
                    status = STATUS_BUFFERING_UNHANDLED_REQUEST
                    data = None
                else:
                    try:
                        self.logger.debug("%s Executing callback %s to process received data", self.__log_prefix__(), callback.__name__)
                        status, data = callback(msg, *args, **kwargs)
                    except Exception:
                        logger.error('{lp} Exception raised. Check callback {callback_name} and it\'s return values for service_id  {service_id} and data_id {data_id}'.format(lp=self.__log_prefix__(), callback_name=callback.__name__, service_id=repr(msg.get_service_id()), data_id=repr(msg.get_data_id())))
                        status = STATUS_CALLBACK_ERROR
                        data = None
            else:
                #
                # RESPONSE RECEIVED
                #
                if callback is None:
                    self.__buffer_received_data__(msg)
                else:
                    self.logger.debug("%s Executing callback %s to process received data", self.__log_prefix__(), callback.__name__)
                    callback(msg, *args, **kwargs)
                return  # No response needed
        self.send(self.__sid_response_dict__[msg.get_service_id()], msg.get_data_id(), data, status=status)

    def __get_message_name__(self, service_id, data_id):
        return 'service: %s, data_id: %s' % (
            self.__sid_name_dict__.get(service_id, repr(service_id)),
            self.__did_name_dict__.get(service_id, {}).get(data_id, repr(data_id)),
        )

    def __get_status_name__(self, status):
        return 'status: %s' % (self.__status_name_dict.get(status, 'unknown status: %s' % repr(status)))

    def __init_channel_name__(self, channel_name):
        self.__comm_inst__.init_channel_name(channel_name)
        self.__callbacks__.init_channel_name(channel_name)
        if channel_name is None:
            self.logger = logging.getLogger(ROOT_LOGGER_NAME).getChild(__name__ + '.' + self.DEFAULT_CHANNEL_NAME)
        else:
            self.logger = logging.getLogger(ROOT_LOGGER_NAME).getChild(__name__ + '.' + channel_name)

    def __log_prefix__(self):
        return 'prot-client:' if self.__comm_inst__.IS_CLIENT else 'prot-server:'

    def __mk_msg__(self, status, service_id, data_id, data):
        return data_storage({data_storage.KEY_DATA_ID: data_id, data_storage.KEY_SERVICE_ID: service_id, data_storage.KEY_STATUS: status, data_storage.KEY_DATA: data})

    def __status_log_lvl__(self, status):
        return STATUS_LOG_LVL.get(status, logging.CRITICAL)

    def add_data(self, service_id, data_id, name):
        """
        Method to add a name for a specific message.

        :param service_id: The Service-ID of the message. See class definitions starting with ``SID_``.
        :type service_id: int or list of ints
        :param data_id: The Data-ID of the message.
        :type data_id: int
        :param name: The Name for the transfered message.
        :type name: str
        """
        try:
            iter(service_id)
        except Exception:
            service_id = (service_id, )

        for sid in service_id:
            if sid not in self.__did_name_dict__:
                self.__did_name_dict__[sid] = {}
            self.__did_name_dict__[sid][data_id] = name

    def add_msg_to_auth_whitelist_(self, service_id, data_id):
        """
        Method to add a specific message to the list, where no authentification is required.

        :param service_id: The Service-ID of the message. See class definitions starting with ``SID_``.
        :type service_id: int
        :param data_id: The Data-ID of the message.
        :type data_id: int
        """
        if service_id not in self.__auth_whitelist__:
            self.__auth_whitelist__[service_id] = []
        self.__auth_whitelist__[service_id].append(data_id)
        logger.debug('%s Adding Message (%s) to the authentification whitelist', self.__log_prefix__(), self.__get_message_name__(service_id, data_id))

    def add_service(self, req_sid, resp_sid, req_name=None, resp_name=None):
        """
        Method to add a Service defined by Request- and Response Serivce-ID.

        :param req_sid: The Request Service-ID.
        :type req_sid: int
        :param resp_sid: The Response Service-ID.
        :type resp_sid: int
        """
        if req_sid in self.__sid_response_dict__:
            logger.error('%s Service with Request-SID=%d and Response-SID=%d not added, because request SID is already registered', self.__log_prefix__(), req_sid, resp_sid)
            raise RequestSidExistsError("Request for this Service is already registered")
        elif resp_sid in self.__sid_response_dict__.values():
            logger.error('%s Service with Request-SID=%d and Response-SID=%d not added, because response SID is already registered', self.__log_prefix__(), req_sid, resp_sid)
            raise ResponseSidExistsError("Response for this Service is already registered")
        else:
            self.__sid_response_dict__[req_sid] = resp_sid
            if req_name is not None:
                self.__sid_name_dict__[req_sid] = req_name
            if resp_name is not None:
                self.__sid_name_dict__[resp_sid] = resp_name
            logger.debug('%s Adding Service with Request=%s and Response=%s', self.__log_prefix__(), req_name or repr(req_sid), resp_name or repr(resp_sid))

    def add_status(self, status, name):
        """
        Method to add a name for a status.

        :param status: The Status. See class definitions starting with ``STATUS_``.
        :type status: int
        :param name: The Name for the Status.
        :type name: str
        """
        self.__status_name_dict[status] = name

    def authentificate(self, timeout=2):
        """
        This method authetificates the client at the server.

        :param timeout: The timeout for the authentification (requesting seed, sending key and getting authentification_feedback).
        :type timeout: float
        :returns: True, if authentification was successfull; False, if not.
        :rtype: bool

        .. note:: An authentification will only processed, if a secret had been given on initialisation.

        .. note:: Client and Server needs to use the same secret.
        """
        if self.__secret__ is not None:
            self.__authentification_state__ = AUTH_STATE_SEED_REQUESTED
            self.send(SID_AUTH_REQUEST, DID_AUTH_SEED, None)
            cnt = 0
            while cnt < timeout * 10:
                time.sleep(0.1)
                if self.__authentification_state__ == AUTH_STATE_TRUSTED_CONNECTION:
                    return True
                elif self.__authentification_state__ == AUTH_STATE_UNTRUSTED_CONNECTION:
                    break
                cnt += 1
        return False

    def check_authentification_state(self):
        """
        This Method return the Authitification State as boolean value.

        :return: True, if authentification state is okay, otherwise False
        :rtype: bool
        """
        return self.__secret__ is None or self.__authentification_state__ == AUTH_STATE_TRUSTED_CONNECTION

    def connection_established(self):
        """
        This Method returns the Connection state including authentification as a boolean value.

        :return: True, if the connection is established (incl. authentification, if a secret has been given)
        :rtype: bool
        """
        return self.is_connected() and (self.__secret__ is None or self.check_authentification_state())

    def is_connected(self):
        """
        This Methods returns Connection state of the Communication Instance :func:`comm_instance.is_connected`.

        :return: True if the :class:`comm_instance` is connected, otherwise False..
        :rtype: bool
        """
        return self.__comm_inst__.is_connected()

    def receive(self, service_id, data_id, timeout=1):
        """
        This Method returns a message object for a defined message or None, if this message is not available after the given timout.

        :param service_id: The Service-ID for the message. See class definitions starting with ``SID_``.
        :type service_id: int
        :param data_id: The Data-ID for the message.
        :type data_id: int
        :param timeout: The timeout for receiving.
        :type timeout: float
        :returns: The received data storage object or None, if no data was received.
        :rtype: data_storage
        """
        data = None
        cnt = 0
        while data is None and cnt < timeout * 10:
            try:
                data = self.__msg_buffer__.get(service_id, {}).get(data_id, []).pop(0)
            except IndexError:
                data = None
            cnt += 1
            time.sleep(0.1)
        if data is None and cnt >= timeout * 10:
            self.logger.warning('%s TIMEOUT (%ss): Requested data (service_id: %s; data_id: %s) not in buffer.', self.__log_prefix__(), repr(timeout), repr(service_id), repr(data_id))
        return data

    def reconnect(self):
        """
        This methods initiates a reconnect by calling :func:`comm_instance.reconnect`.
        """
        return self.__comm_inst__.reconnect()

    def register_callback(self, service_id, data_id, callback, *args, **kwargs):
        """
        This method registers a callback for the given parameters. Giving ``None`` means, that all Service-IDs or all Data-IDs are used.
        If a message hitting these parameters has been received, the callback will be executed.

        :param service_id: The Service-ID for the message. See class definitions starting with ``SID_``.
        :type service_id: int
        :param data_id: The Data-ID for the message.
        :type data_id: int

        .. note:: The :func:`callback` is priorised in the following order:

            * Callbacks with defined Service-ID and Data-ID.
            * Callbacks with a defined Service-ID and all Data-IDs.
            * Callbacks with a defined Data-ID and all Service-IDs.
            * Unspecific Callbacks.

        .. note:: The :func:`callback` is executed with these arguments:

            **Parameters given at the callback call:**

            * The first Arguments is the received message as :class:`data_storage` object.
            * Further arguments given at registration.
            * Further keyword arguments given at registration.

            **Return value of the callback:**

            If the Callback is a Request Callback for a registered Service, the return value has to be a tuple or list with

            * :const:`response_status`: The response status (see class definitions starting with :const:`STA_*`.
            * :const:`response_data`: A JSON iterable object to be used as data for the response.

        .. note:: Only registered services will respond via the callbacks return values with the same data_id.
        """
        self.__callbacks__.add(service_id, data_id, callback, *args, **kwargs)

    def send(self, service_id, data_id, data, status=STATUS_OKAY, timeout=2):
        """
        This methods sends out a message with the given content.

        :param service_id: The Service-ID for the message. See class definitions starting with ``SERVICE_``.
        :type service_id: int
        :param data_id: The Data-ID for the message.
        :type data_id: int
        :param data: The data to be transfered. The data needs to be json compatible.
        :type data: str
        :param status: The Status for the message. All requests should have ``STATUS_OKAY``.
        :type status: int
        :param timeout: The timeout for sending data (e.g. time to establish new connection).
        :type timeout: float
        :return: True if data had been sent, otherwise False.
        :rtype: bool
        """
        if (self.check_authentification_state() or not self.__authentification_required__(service_id, data_id)) or (service_id in self.__sid_response_dict__.values() and status == STATUS_AUTH_REQUIRED and data is None):
            msg = data_storage(service_id=service_id, data_id=data_id, data=data, status=status)
            self.__log_msg__(msg, 'TX ->')
            return self.__comm_inst__.send(self.__build_frame__(msg), timeout=timeout)
        else:
            # Authentification required
            self.logger.warning("%s Authentification is required. TX-Message %s, %s, data: %s will be ignored.", self.__log_prefix__(), self.__get_message_name__(service_id, data_id), self.__get_status_name__(status), repr(data))
            return False


class struct_json_protocol(pure_json_protocol):
    """
    This Class has the same functionality like :class:`pure_json_protocol`. The message length is less than for :class:`pure_json_protocol`, but the functionality and compatibility is reduced.
    See also parent :py:class:`pure_json_protocol`.

    .. note::
        This class is depreceated and here for compatibility reasons (to support old clients or servers). Usage of :class:`pure_json_protocol` is recommended.
    """
    def __init__(self, *args, **kwargs):
        pure_json_protocol.__init__(self, *args, **kwargs)

    def __analyse_frame__(self, frame):
        status, service_id, data_id = struct.unpack('>III', frame[0:12])
        if sys.version_info >= (3, 0):
            data = json.loads(frame[12:-1].decode('utf-8'))
        else:
            data = json.loads(frame[12:-1])
        return self.__mk_msg__(status, service_id, data_id, data)

    def __build_frame__(self, msg):
        frame = struct.pack('>III', msg.get_status(), msg.get_service_id(), msg.get_data_id())
        if sys.version_info >= (3, 0):
            frame += bytes(json.dumps(msg.get_data()), 'utf-8')
            frame += self.__calc_chksum__(frame)
        else:
            frame += json.dumps(msg.get_data())
            frame += self.__calc_chksum__(frame)
        return frame

    def __calc_chksum__(self, raw_data):
        chksum = 0
        for b in raw_data:
            if sys.version_info >= (3, 0):
                chksum ^= b
            else:
                chksum ^= ord(b)
        if sys.version_info >= (3, 0):
            return bytes([chksum])
        else:
            return chr(chksum)

    def __check_frame_checksum__(self, frame):
        return self.__calc_chksum__(frame[:-1]) == frame[-1:]