diff --git a/frappy/io.py b/frappy/io.py
index 307fa97..d2cca96 100644
--- a/frappy/io.py
+++ b/frappy/io.py
@@ -63,7 +63,7 @@ class HasIO(Module):
                 io = self.ioClass(ioname, srv.log.getChild(ioname), opts, srv)  # pylint: disable=not-callable
                 io.callingModule = []
                 srv.modules[ioname] = io
-                srv.dispatcher.register_module(io, ioname)
+                srv.secnode.add_module(io, ioname)
                 self.ioDict[self.uri] = ioname
             self.io = ioname
 
diff --git a/frappy/logging.py b/frappy/logging.py
index 085ec8c..be3bcb2 100644
--- a/frappy/logging.py
+++ b/frappy/logging.py
@@ -55,6 +55,8 @@ class RemoteLogHandler(mlzlog.Handler):
     def __init__(self):
         super().__init__()
         self.subscriptions = {}  # dict[modname] of tuple(mobobj, dict [conn] of level)
+        # None will be replaced by a callback when one is first installed
+        self.send_log = None
 
     def emit(self, record):
         """unused"""
@@ -62,18 +64,18 @@ class RemoteLogHandler(mlzlog.Handler):
     def handle(self, record):
         modname = record.name.split('.')[-1]
         try:
-            modobj, subscriptions = self.subscriptions[modname]
+            subscriptions = self.subscriptions[modname]
         except KeyError:
             return
         for conn, lev in subscriptions.items():
             if record.levelno >= lev:
-                modobj.DISPATCHER.send_log_msg(
-                    conn, modobj.name, LEVEL_NAMES[record.levelno],
+                self.send_log(  # pylint: disable=not-callable
+                    conn, modname, LEVEL_NAMES[record.levelno],
                     record.getMessage())
 
-    def set_conn_level(self, modobj, conn, level):
+    def set_conn_level(self, modname, conn, level):
         level = check_level(level)
-        modobj, subscriptions = self.subscriptions.setdefault(modobj.name, (modobj, {}))
+        subscriptions = self.subscriptions.setdefault(modname, {})
         if level == OFF:
             subscriptions.pop(conn, None)
         else:
@@ -127,7 +129,7 @@ class HasComlog:
         if self.comlog and generalConfig.initialized and generalConfig.comlog:
             self._comLog = mlzlog.Logger(f'COMLOG.{self.name}')
             self._comLog.handlers[:] = []
-            directory = join(logger.logdir, logger.rootname, 'comlog', self.DISPATCHER.name)
+            directory = join(logger.logdir, logger.rootname, 'comlog', self.secNode.name)
             self._comLog.addHandler(ComLogfileHandler(
                 directory, self.name, max_days=generalConfig.getint('comlog_days', 7)))
             return
diff --git a/frappy/modulebase.py b/frappy/modulebase.py
new file mode 100644
index 0000000..9d25648
--- /dev/null
+++ b/frappy/modulebase.py
@@ -0,0 +1,858 @@
+# *****************************************************************************
+#
+# This program is free software; you can redistribute it and/or modify it under
+# the terms of the GNU General Public License as published by the Free Software
+# Foundation; either version 2 of the License, or (at your option) any later
+# version.
+#
+# This program is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+# FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+# details.
+#
+# You should have received a copy of the GNU General Public License along with
+# this program; if not, write to the Free Software Foundation, Inc.,
+# 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+#
+# Module authors:
+#   Enrico Faulhaber <enrico.faulhaber@frm2.tum.de>
+#   Markus Zolliker <markus.zolliker@psi.ch>
+#   Alexander Zaft <a.zaft@fz-juelich.de>
+#
+# *****************************************************************************
+"""Defines the base Module class"""
+
+
+import time
+import threading
+from collections import OrderedDict
+
+from frappy.datatypes import ArrayOf, BoolType, EnumType, FloatRange, \
+    IntRange, StringType, TextType, TupleOf, \
+    NoneOr
+from frappy.errors import BadValueError, CommunicationFailedError, ConfigError, \
+    ProgrammingError, SECoPError, secop_error, RangeError
+from frappy.lib import formatException, mkthread, UniqueObject
+from frappy.params import Accessible, Command, Parameter, Limit
+from frappy.properties import HasProperties, Property
+from frappy.logging import RemoteLogHandler
+
+# TODO: resolve cirular import
+# from .interfaces import SECoP_BASE_CLASSES
+# WORKAROUND:
+SECoP_BASE_CLASSES = ['Readable', 'Writable', 'Drivable', 'Communicator']
+
+Done = UniqueObject('Done')
+"""a special return value for a read_<param>/write_<param> method
+
+indicating that the setter is triggered already"""
+
+wrapperClasses = {}
+
+
+class HasAccessibles(HasProperties):
+    """base class of Module
+
+    joining the class's properties, parameters and commands dicts with
+    those of base classes.
+    wrap read_*/write_* methods
+    (so the dispatcher will get notified of changed values)
+    """
+    isWrapped = False
+    checkedMethods = set()
+
+    @classmethod
+    def __init_subclass__(cls):  # pylint: disable=too-many-branches
+        super().__init_subclass__()
+        if cls.isWrapped:
+            return
+        # merge accessibles from all sub-classes, treat overrides
+        # for now, allow to use also the old syntax (parameters/commands dict)
+        accessibles = OrderedDict()  # dict of accessibles
+        merged_properties = {}  # dict of dict of merged properties
+        new_names = []  # list of names of new accessibles
+        override_values = {}  # bare values overriding a parameter and methods overriding a command
+
+        for base in reversed(cls.__mro__):
+            for key, value in base.__dict__.items():
+                if isinstance(value, Accessible):
+                    value.updateProperties(merged_properties.setdefault(key, {}))
+                    if base == cls and key not in accessibles:
+                        new_names.append(key)
+                    accessibles[key] = value
+                    override_values.pop(key, None)
+                elif key in accessibles:
+                    override_values[key] = value
+        for aname, aobj in list(accessibles.items()):
+            if aname in override_values:
+                aobj = aobj.copy()
+                value = override_values[aname]
+                if value is None:
+                    accessibles.pop(aname)
+                    continue
+                aobj.merge(merged_properties[aname])
+                aobj.override(value)
+                # replace the bare value by the created accessible
+                setattr(cls, aname, aobj)
+            else:
+                aobj.merge(merged_properties[aname])
+            accessibles[aname] = aobj
+
+        # rebuild order: (1) inherited items, (2) items from paramOrder, (3) new accessibles
+        # move (2) to the end
+        paramOrder = cls.__dict__.get('paramOrder', ())
+        for aname in paramOrder:
+            if aname in accessibles:
+                accessibles.move_to_end(aname)
+                # ignore unknown names
+        # move (3) to the end
+        for aname in new_names:
+            if aname not in paramOrder:
+                accessibles.move_to_end(aname)
+        # note: for python < 3.6 the order of inherited items is not ensured between
+        # declarations within the same class
+        cls.accessibles = accessibles
+
+        cls.wrappedAttributes = {'isWrapped': True}
+        # create wrappers for access methods
+        wrapped_name = '_' + cls.__name__
+        for pname, pobj in accessibles.items():
+            # wrap of reading/writing funcs
+            if not isinstance(pobj, Parameter):
+                # nothing to do for Commands
+                continue
+
+            rname = 'read_' + pname
+            rfunc = getattr(cls, rname, None)
+            # create wrapper
+            if rfunc:
+
+                def new_rfunc(self, pname=pname, rfunc=rfunc):
+                    with self.accessLock:
+                        try:
+                            value = rfunc(self)
+                            self.log.debug("read_%s returned %r", pname, value)
+                            if value is Done:  # TODO: to be removed when all code using Done is updated
+                                return getattr(self, pname)
+                            pobj = self.accessibles[pname]
+                            value = pobj.datatype(value)
+                        except Exception as e:
+                            self.log.debug("read_%s failed with %r", pname, e)
+                            if isinstance(e, SECoPError):
+                                e.raising_methods.append(f'{self.name}.read_{pname}')
+                            self.announceUpdate(pname, err=e)
+                            raise
+                        self.announceUpdate(pname, value, validate=False)
+                        return value
+
+                new_rfunc.poll = getattr(rfunc, 'poll', True)
+            else:
+
+                def new_rfunc(self, pname=pname):
+                    return getattr(self, pname)
+
+                new_rfunc.poll = False
+
+            new_rfunc.__name__ = rname
+            new_rfunc.__qualname__ = wrapped_name + '.' + rname
+            new_rfunc.__module__ = cls.__module__
+            cls.wrappedAttributes[rname] = new_rfunc
+
+            cname = 'check_' + pname
+            for postfix in ('_limits', '_min', '_max'):
+                limname = pname + postfix
+                if limname in accessibles:
+                    # find the base class, where the parameter <limname> is defined first.
+                    # we have to check all bases, as they may not be treated yet when
+                    # not inheriting from HasAccessibles
+                    base = next(b for b in reversed(cls.__mro__) if limname in b.__dict__)
+                    if cname not in base.__dict__:
+                        # there is no check method yet at this class
+                        # add check function to the class where the limit was defined
+                        setattr(base, cname, lambda self, value, pname=pname: self.checkLimits(value, pname))
+
+            cfuncs = tuple(filter(None, (b.__dict__.get(cname) for b in cls.__mro__)))
+            wname = 'write_' + pname
+            wfunc = getattr(cls, wname, None)
+            if wfunc or not pobj.readonly:
+                # allow write method even when parameter is readonly, but internally writable
+
+                def new_wfunc(self, value, pname=pname, wfunc=wfunc, check_funcs=cfuncs):
+                    with self.accessLock:
+                        self.log.debug('validate %r to datatype of %r', value, pname)
+                        validate = self.parameters[pname].datatype.validate
+                        try:
+                            new_value = validate(value)
+                            for c in check_funcs:
+                                if c(self, value):
+                                    break
+                            if wfunc:
+                                new_value = wfunc(self, new_value)
+                                self.log.debug('write_%s(%r) returned %r', pname, value, new_value)
+                                if new_value is Done:  # TODO: to be removed when all code using Done is updated
+                                    return getattr(self, pname)
+                                new_value = value if new_value is None else validate(new_value)
+                        except Exception as e:
+                            if isinstance(e, SECoPError):
+                                e.raising_methods.append(f'{self.name}.write_{pname}')
+                            self.announceUpdate(pname, err=e)
+                            raise
+                        self.announceUpdate(pname, new_value, validate=False)
+                        return new_value
+
+                new_wfunc.__name__ = wname
+                new_wfunc.__qualname__ = wrapped_name + '.' + wname
+                new_wfunc.__module__ = cls.__module__
+                cls.wrappedAttributes[wname] = new_wfunc
+
+        cls.checkedMethods.update(cls.wrappedAttributes)
+
+        # check for programming errors
+        for attrname in dir(cls):
+            prefix, _, pname = attrname.partition('_')
+            if not pname:
+                continue
+            if prefix == 'do':
+                raise ProgrammingError(f'{cls.__name__!r}: old style command {attrname!r} not supported anymore')
+            if prefix in ('read', 'write') and attrname not in cls.checkedMethods:
+                raise ProgrammingError(f'{cls.__name__}.{attrname} defined, but {pname!r} is no parameter')
+
+        try:
+            # update Status type
+            cls.Status = cls.status.datatype.members[0]._enum
+        except AttributeError:
+            pass
+        res = {}
+        # collect info about properties
+        for pn, pv in cls.propertyDict.items():
+            if pv.settable:
+                res[pn] = pv
+        # collect info about parameters and their properties
+        for param, pobj in cls.accessibles.items():
+            res[param] = {}
+            for pn, pv in pobj.getProperties().items():
+                if pv.settable:
+                    res[param][pn] = pv
+        cls.configurables = res
+
+    def __new__(cls, *args, **kwds):
+        wrapper_class = wrapperClasses.get(cls)
+        if wrapper_class is None:
+            wrapper_class = type('_' + cls.__name__, (cls,), cls.wrappedAttributes)
+            wrapperClasses[cls] = wrapper_class
+        return super().__new__(wrapper_class)
+
+
+class Feature(HasAccessibles):
+    """all things belonging to a small, predefined functionality influencing the working of a module
+
+    a mixin with Feature as a direct base class is recognized as a SECoP feature
+    and reported in the module property 'features'
+    """
+
+
+class PollInfo:
+    def __init__(self, pollinterval, trigger_event):
+        self.interval = pollinterval
+        self.last_main = 0
+        self.last_slow = 0
+        self.pending_errors = set()
+        self.polled_parameters = []
+        self.fast_flag = False
+        self.trigger_event = trigger_event
+
+    def trigger(self, immediate=False):
+        """trigger a recalculation of poll due times
+
+        :param immediate: when True, doPoll should be called as soon as possible
+        """
+        if immediate:
+            self.last_main = 0
+        self.trigger_event.set()
+
+    def update_interval(self, pollinterval):
+        if not self.fast_flag:
+            self.interval = pollinterval
+            self.trigger()
+
+
+class Module(HasAccessibles):
+    """basic module
+
+    all SECoP modules derive from this.
+
+    :param name: the modules name
+    :param logger: a logger instance
+    :param cfgdict: the dict from this modules section in the config file
+    :param srv: the server instance
+
+    Notes:
+
+    - the programmer normally should not need to reimplement :meth:`__init__`
+    - within modules, parameters should only be addressed as ``self.<pname>``,
+      i.e. ``self.value``, ``self.target`` etc...
+
+      - these are accessing the cached version.
+      - they can also be written to, generating an async update
+
+    - if you want to 'update from the hardware', call ``self.read_<pname>()`` instead
+
+      - the return value of this method will be used as the new cached value and
+        be an async update sent automatically.
+
+    - if you want to 'update the hardware' call ``self.write_<pname>(<new value>)``.
+
+      - The return value of this method will also update the cache.
+
+    """
+    # static properties, definitions in derived classes should overwrite earlier ones.
+    # note: properties don't change after startup and are usually filled
+    #       with data from a cfg file...
+    # note: only the properties predefined here are allowed to be set in the cfg file
+    export = Property('flag if this module is to be exported', BoolType(), default=True, export=False)
+    group = Property('optional group the module belongs to', StringType(), default='', extname='group')
+    description = Property('description of the module', TextType(), extname='description', mandatory=True)
+    meaning = Property('optional meaning indicator', TupleOf(StringType(), IntRange(0, 50)),
+                       default=('', 0), extname='meaning')
+    visibility = Property('optional visibility hint', EnumType('visibility', user=1, advanced=2, expert=3),
+                          default='user', extname='visibility')
+    implementation = Property('internal name of the implementation class of the module', StringType(),
+                              extname='implementation')
+    interface_classes = Property('offical highest interface-class of the module', ArrayOf(StringType()),
+                                 extname='interface_classes')
+    features = Property('list of features', ArrayOf(StringType()), extname='features')
+    pollinterval = Property('poll interval for parameters handled by doPoll', FloatRange(0.1, 120), default=5)
+    slowinterval = Property('poll interval for other parameters', FloatRange(0.1, 120), default=15)
+    omit_unchanged_within = Property('default for minimum time between updates of unchanged values',
+                                     NoneOr(FloatRange(0)), export=False, default=None)
+    enablePoll = True
+
+    pollInfo = None
+    triggerPoll = None  # trigger event for polls. used on io modules and modules without io
+
+    def __init__(self, name, logger, cfgdict, srv):
+        # remember the secnode for interacting with other modules and the
+        # server
+        self.secNode = srv.secnode
+        self.log = logger
+        self.name = name
+        self.valueCallbacks = {}
+        self.errorCallbacks = {}
+        self.earlyInitDone = False
+        self.initModuleDone = False
+        self.startModuleDone = False
+        self.remoteLogHandler = None
+        self.accessLock = threading.RLock()  # for read_* / write_* methods
+        self.updateLock = threading.RLock()  # for announceUpdate
+        self.polledModules = []  # modules polled by thread started in self.startModules
+        self.attachedModules = {}
+        self.errors = []
+        self._isinitialized = False
+        self.updateCallback =  srv.dispatcher.announce_update
+
+        # handle module properties
+        # 1) make local copies of properties
+        super().__init__()
+
+        # conversion from exported names to internal attribute names
+        self.accessiblename2attr = {}
+        self.writeDict = {}  # values of parameters to be written
+        # properties, parameters and commands are auto-merged upon subclassing
+        self.parameters = {}
+        self.commands = {}
+
+        # 2) check and apply properties specified in cfgdict as
+        # '<propertyname> = <propertyvalue>'
+        # pylint: disable=consider-using-dict-items
+        for key in self.propertyDict:
+            value = cfgdict.pop(key, None)
+            if value is not None:
+                try:
+                    if isinstance(value, dict):
+                        self.setProperty(key, value['value'])
+                    else:
+                        self.setProperty(key, value)
+                except BadValueError:
+                    self.errors.append(f'{key}: value {value!r} does not match {self.propertyDict[key].datatype!r}!')
+
+        # 3) set automatic properties
+        mycls, = self.__class__.__bases__  # skip the wrapper class
+        myclassname = f'{mycls.__module__}.{mycls.__name__}'
+        self.implementation = myclassname
+
+        # list of only the 'highest' secop module class
+        self.interface_classes = [
+            b.__name__ for b in mycls.__mro__ if b.__name__ in SECoP_BASE_CLASSES][:1]
+
+        # handle Features
+        self.features = [b.__name__ for b in mycls.__mro__ if Feature in b.__bases__]
+
+        # handle accessibles
+        # 1) make local copies of parameter objects
+        #    they need to be individual per instance since we use them also
+        #    to cache the current value + qualifiers...
+        # do not re-use self.accessibles as this is the same for all instances
+        accessibles = self.accessibles
+        self.accessibles = {}
+        for aname, aobj in accessibles.items():
+            # make a copy of the Parameter/Command object
+            aobj = aobj.copy()
+            acfg = cfgdict.pop(aname, None)
+            self._add_accessible(aname, aobj, cfg=acfg)
+
+        # 3) complain about names not found as accessible or property names
+        if cfgdict:
+            self.errors.append(
+                f"{', '.join(cfgdict.keys())} does not exist (use one of"
+                f" {', '.join(list(self.accessibles) + list(self.propertyDict))})")
+
+        # 5) ensure consistency of all accessibles added here
+        for aobj in self.accessibles.values():
+            aobj.finish(self)
+
+        # Modify units AFTER applying the cfgdict
+        mainvalue = self.parameters.get('value')
+        if mainvalue:
+            mainunit = mainvalue.datatype.unit
+            if mainunit:
+                self.applyMainUnit(mainunit)
+
+        # 6) check complete configuration of * properties
+        if not self.errors:
+            try:
+                self.checkProperties()
+            except ConfigError as e:
+                self.errors.append(str(e))
+            for aname, aobj in self.accessibles.items():
+                try:
+                    aobj.checkProperties()
+                except (ConfigError, ProgrammingError) as e:
+                    self.errors.append(f'{aname}: {e}')
+        if self.errors:
+            raise ConfigError(self.errors)
+
+    # helper cfg-editor
+    def __iter__(self):
+        return self.accessibles.__iter__()
+
+    def __getitem__(self, item):
+        return self.accessibles.__getitem__(item)
+
+    def applyMainUnit(self, mainunit):
+        """replace $ in units of parameters by mainunit"""
+        for pobj in self.parameters.values():
+            pobj.datatype.set_main_unit(mainunit)
+
+    def _add_accessible(self, name, accessible, cfg=None):
+        if self.startModuleDone:
+            raise ProgrammingError('Accessibles can only be added before startModule()!')
+        if not self.export:  # do not export parameters of a module not exported
+            accessible.export = False
+        self.accessibles[name] = accessible
+        if accessible.export:
+            self.accessiblename2attr[accessible.export] = name
+        if isinstance(accessible, Parameter):
+            self.parameters[name] = accessible
+        if isinstance(accessible, Command):
+            self.commands[name] = accessible
+        if cfg:
+            try:
+                for propname, propvalue in cfg.items():
+                    accessible.setProperty(propname, propvalue)
+            except KeyError:
+                self.errors.append(f"'{name}' has no property '{propname}'")
+            except BadValueError as e:
+                self.errors.append(f'{name}.{propname}: {str(e)}')
+        if isinstance(accessible, Parameter):
+            self._handle_writes(name, accessible)
+
+    def _handle_writes(self, pname, pobj):
+        """ register value for writing, if given
+        apply default when no value is given (in cfg or as Parameter argument)
+        or complain, when cfg is needed
+        """
+        self.valueCallbacks[pname] = []
+        self.errorCallbacks[pname] = []
+        if isinstance(pobj, Limit):
+            basepname = pname.rpartition('_')[0]
+            baseparam = self.parameters.get(basepname)
+            if not baseparam:
+                self.errors.append(f'limit {pname!r} is given, but not {basepname!r}')
+                return
+            if baseparam.datatype is None:
+                return  # an error will be reported on baseparam
+            pobj.set_datatype(baseparam.datatype)
+        if not pobj.hasDatatype():
+            self.errors.append(f'{pname} needs a datatype')
+            return
+        if pobj.value is None:
+            if pobj.needscfg:
+                self.errors.append(f'{pname!r} has no default value and was not given in config!')
+            if pobj.default is None:
+                # we do not want to call the setter for this parameter for now,
+                # this should happen on the first read
+                pobj.readerror = ConfigError(f'parameter {pname!r} not initialized')
+                # above error will be triggered on activate after startup,
+                # when not all hardware parameters are read because of startup timeout
+                pobj.default = pobj.datatype.default
+            pobj.value = pobj.default
+        else:
+            # value given explicitly, either by cfg or as Parameter argument
+            pobj.given = True  # for PersistentMixin
+            if hasattr(self, 'write_' + pname):
+                self.writeDict[pname] = pobj.value
+            if pobj.default is None:
+                pobj.default = pobj.value
+            # this checks again for datatype and sets the timestamp
+            setattr(self, pname, pobj.value)
+
+    def announceUpdate(self, pname, value=None, err=None, timestamp=None, validate=True):
+        """announce a changed value or readerror
+
+        :param pname: parameter name
+        :param value: new value or None in case of error
+        :param err: None or an exception
+        :param timestamp: a timestamp or None for taking current time
+        :param validate: True: convert to datatype, in case of error store in readerror
+        :return:
+
+        when err=None and validate=False, the value must already be converted to the datatype
+        """
+
+        with self.updateLock:
+            pobj = self.parameters[pname]
+            timestamp = timestamp or time.time()
+            if not err:
+                try:
+                    if validate:
+                        value = pobj.datatype(value)
+                except Exception as e:
+                    err = e
+                else:
+                    changed = pobj.value != value
+                    # store the value even in case of error
+                    pobj.value = value
+            if err:
+                if secop_error(err) == pobj.readerror:
+                    err.report_error = False
+                    return  # no updates for repeated errors
+                err = secop_error(err)
+            elif not changed and timestamp < (pobj.timestamp or 0) + pobj.omit_unchanged_within:
+                # no change within short time -> omit
+                return
+            pobj.timestamp = timestamp or time.time()
+            if err:
+                callbacks = self.errorCallbacks
+                pobj.readerror = arg = err
+            else:
+                callbacks = self.valueCallbacks
+                arg = value
+                pobj.readerror = None
+            if pobj.export:
+                self.updateCallback(self.name, pname, pobj)
+            cblist = callbacks[pname]
+            for cb in cblist:
+                try:
+                    cb(arg)
+                except Exception:
+                    # print(formatExtendedTraceback())
+                    pass
+
+    def registerCallbacks(self, modobj, autoupdate=()):
+        """register callbacks to another module <modobj>
+
+        - whenever a self.<param> changes:
+          <modobj>.update_<param> is called with the new value as argument.
+          If this method raises an exception, <modobj>.<param> gets into an error state.
+          If the method does not exist and <param> is in autoupdate,
+          <modobj>.<param> is updated to self.<param>
+        - whenever <self>.<param> gets into an error state:
+          <modobj>.error_update_<param> is called with the exception as argument.
+          If this method raises an error, <modobj>.<param> gets into an error state.
+          If this method does not exist, and <param> is in autoupdate,
+          <modobj>.<param> gets into the same error state as self.<param>
+        """
+        for pname in self.parameters:
+            errfunc = getattr(modobj, 'error_update_' + pname, None)
+            if errfunc:
+                def errcb(err, p=pname, efunc=errfunc):
+                    try:
+                        efunc(err)
+                    except Exception as e:
+                        modobj.announceUpdate(p, err=e)
+                self.errorCallbacks[pname].append(errcb)
+            else:
+                def errcb(err, p=pname):
+                    modobj.announceUpdate(p, err=err)
+                if pname in autoupdate:
+                    self.errorCallbacks[pname].append(errcb)
+
+            updfunc = getattr(modobj, 'update_' + pname, None)
+            if updfunc:
+                def cb(value, ufunc=updfunc, efunc=errcb):
+                    try:
+                        ufunc(value)
+                    except Exception as e:
+                        efunc(e)
+                self.valueCallbacks[pname].append(cb)
+            elif pname in autoupdate:
+                def cb(value, p=pname):
+                    modobj.announceUpdate(p, value)
+                self.valueCallbacks[pname].append(cb)
+
+    def isBusy(self, status=None):
+        """helper function for treating substates of BUSY correctly"""
+        # defined even for non drivable (used for dynamic polling)
+        return False
+
+    def earlyInit(self):
+        """initialise module with stuff to be done before all modules are created"""
+        self.earlyInitDone = True
+
+    def initModule(self):
+        """initialise module with stuff to be done after all modules are created"""
+        self.initModuleDone = True
+        if self.enablePoll or self.writeDict:
+            # enablePoll == False: we still need the poll thread for writing values from writeDict
+            if hasattr(self, 'io'):
+                self.io.polledModules.append(self)
+            else:
+                self.triggerPoll = threading.Event()
+                self.polledModules.append(self)
+
+    def startModule(self, start_events):
+        """runs after init of all modules
+
+        when a thread is started, a trigger function may signal that it
+        has finished its initial work
+        start_events.get_trigger(<timeout>) creates such a trigger and
+        registers it in the server for waiting
+        <timeout> defaults to 30 seconds
+        """
+        # we do not need self.errors any longer. should we delete it?
+        # del self.errors
+        if self.polledModules:
+            mkthread(self.__pollThread, self.polledModules, start_events.get_trigger())
+        self.startModuleDone = True
+
+    def initialReads(self):
+        """initial reads to be done
+
+        override to read initial values from HW, when it is not desired
+        to poll them afterwards
+
+        called from the poll thread, after writeInitParams but before
+        all parameters are polled once
+        """
+
+    def shutdownModule(self):
+        """called when the sever shuts down
+
+        any cleanup-work should be performed here, like closing threads and
+        saving data.
+        """
+
+    def doPoll(self):
+        """polls important parameters like value and status
+
+        all other parameters are polled automatically
+        """
+
+    def setFastPoll(self, flag, fast_interval=0.25):
+        """change poll interval
+
+        :param flag: enable/disable fast poll mode
+        :param fast_interval: fast poll interval
+        """
+        if self.pollInfo:
+            self.pollInfo.fast_flag = flag
+            self.pollInfo.interval = fast_interval if flag else self.pollinterval
+            self.pollInfo.trigger()
+
+    def callPollFunc(self, rfunc, raise_com_failed=False):
+        """call read method with proper error handling"""
+        try:
+            rfunc()
+            if rfunc.__name__ in self.pollInfo.pending_errors:
+                self.log.info('%s: o.k.', rfunc.__name__)
+                self.pollInfo.pending_errors.discard(rfunc.__name__)
+        except Exception as e:
+            if getattr(e, 'report_error', True):
+                name = rfunc.__name__
+                self.pollInfo.pending_errors.add(name)  # trigger o.k. message after error is resolved
+                if isinstance(e, SECoPError):
+                    e.raising_methods.append(name)
+                    if e.silent:
+                        self.log.debug('%s', e.format(False))
+                    else:
+                        self.log.error('%s', e.format(False))
+                    if raise_com_failed and isinstance(e, CommunicationFailedError):
+                        raise
+                else:
+                    # not a SECoPError: this is proabably a programming error
+                    # we want to log the traceback
+                    self.log.error('%s', formatException())
+
+    def __pollThread(self, modules, started_callback):
+        """poll thread body
+
+        :param modules: list of modules to be handled by this thread
+        :param started_callback: to be called after all polls are done once
+
+        before polling, parameters which need hardware initialisation are written
+        """
+        polled_modules = [m for m in modules if m.enablePoll]
+        if hasattr(self, 'registerReconnectCallback'):
+            # self is a communicator supporting reconnections
+            def trigger_all(trg=self.triggerPoll, polled_modules=polled_modules):
+                for m in polled_modules:
+                    m.pollInfo.last_main = 0
+                    m.pollInfo.last_slow = 0
+                trg.set()
+            self.registerReconnectCallback('trigger_polls', trigger_all)
+
+        # collect all read functions
+        for mobj in polled_modules:
+            pinfo = mobj.pollInfo = PollInfo(mobj.pollinterval, self.triggerPoll)
+            # trigger a poll interval change when self.pollinterval changes.
+            if 'pollinterval' in mobj.valueCallbacks:
+                mobj.valueCallbacks['pollinterval'].append(pinfo.update_interval)
+
+            for pname, pobj in mobj.parameters.items():
+                rfunc = getattr(mobj, 'read_' + pname)
+                if rfunc.poll:
+                    pinfo.polled_parameters.append((mobj, rfunc, pobj))
+        while True:
+            try:
+                for mobj in modules:
+                    # TODO when needed: here we might add a call to a method :meth:`beforeWriteInit`
+                    mobj.writeInitParams()
+                    mobj.initialReads()
+                # call all read functions a first time
+                for m in polled_modules:
+                    for mobj, rfunc, _ in m.pollInfo.polled_parameters:
+                        mobj.callPollFunc(rfunc, raise_com_failed=True)
+                # TODO when needed: here we might add calls to a method :meth:`afterInitPolls`
+                break
+            except CommunicationFailedError as e:
+                # when communication failed, probably all parameters and may be more modules are affected.
+                # as this would take a lot of time (summed up timeouts), we do not continue
+                # trying and let the server accept connections, further polls might success later
+                if started_callback:
+                    self.log.error('communication failure on startup: %s', e)
+                    started_callback()
+                    started_callback = None
+            self.triggerPoll.wait(0.1)  # wait for reconnection or max 10 sec.
+            break
+        if started_callback:
+            started_callback()
+        if not polled_modules:  # no polls needed - exit thread
+            return
+        to_poll = ()
+        while True:
+            now = time.time()
+            wait_time = 999
+            for mobj in modules:
+                pinfo = mobj.pollInfo
+                wait_time = min(pinfo.last_main + pinfo.interval - now, wait_time,
+                                pinfo.last_slow + mobj.slowinterval - now)
+            if wait_time > 0 and not to_poll:
+                # nothing to do
+                self.triggerPoll.wait(wait_time)
+                self.triggerPoll.clear()
+                continue
+            # call doPoll of all modules where due
+            for mobj in modules:
+                pinfo = mobj.pollInfo
+                if now > pinfo.last_main + pinfo.interval:
+                    try:
+                        pinfo.last_main = (now // pinfo.interval) * pinfo.interval
+                    except ZeroDivisionError:
+                        pinfo.last_main = now
+                    mobj.callPollFunc(mobj.doPoll)
+                now = time.time()
+            # find ONE due slow poll and call it
+            loop = True
+            while loop:  # loops max. 2 times, when to_poll is at end
+                for mobj, rfunc, pobj in to_poll:
+                    if now > pobj.timestamp + mobj.slowinterval * 0.5:
+                        mobj.callPollFunc(rfunc)
+                        loop = False  # one poll done
+                        break
+                else:
+                    to_poll = []
+                    # collect due slow polls
+                    for mobj in modules:
+                        pinfo = mobj.pollInfo
+                        if now > pinfo.last_slow + mobj.slowinterval:
+                            to_poll.extend(pinfo.polled_parameters)
+                            pinfo.last_slow = (now // mobj.slowinterval) * mobj.slowinterval
+                    if to_poll:
+                        to_poll = iter(to_poll)
+                    else:
+                        loop = False  # no slow polls ready
+
+    def writeInitParams(self):
+        """write values for parameters with configured values
+
+        - does proper error handling
+
+        called at the beginning of the poller thread and for writing persistent values
+        """
+        for pname in list(self.writeDict):
+            value = self.writeDict.pop(pname, Done)
+            # in the mean time, a poller or handler might already have done it
+            if value is not Done:
+                wfunc = getattr(self, 'write_' + pname, None)
+                if wfunc is None:
+                    setattr(self, pname, value)
+                else:
+                    try:
+                        self.log.debug('initialize parameter %s', pname)
+                        wfunc(value)
+                    except SECoPError as e:
+                        if e.silent:
+                            self.log.debug('%s: %s', pname, str(e))
+                        else:
+                            self.log.error('%s: %s', pname, str(e))
+                    except Exception:
+                        self.log.error(formatException())
+
+    def setRemoteLogging(self, conn, level, send_log):
+        if self.remoteLogHandler is None:
+            for handler in self.log.handlers:
+                if isinstance(handler, RemoteLogHandler):
+                    handler.send_log = send_log
+                    self.remoteLogHandler = handler
+                    break
+            else:
+                raise ValueError('remote handler not found')
+        self.remoteLogHandler.set_conn_level(self.name, conn, level)
+
+    def checkLimits(self, value, pname='target'):
+        """check for limits
+
+        :param value: the value to be checked for <pname>_min <= value <= <pname>_max
+        :param pname: parameter name, default is 'target'
+
+        raises RangeError in case the value is not valid
+
+        This method is called automatically and needs therefore rarely to be
+        called by the programmer. It might be used in a check_<param> method,
+        when no automatic super call is desired.
+        """
+        try:
+            min_, max_ = getattr(self, pname + '_limits')
+            if not min_ <= value <= max_:
+                raise RangeError(f'{pname} outside {pname}_limits')
+            return
+        except AttributeError:
+            pass
+        min_ = getattr(self, pname + '_min', float('-inf'))
+        max_ = getattr(self, pname + '_max', float('inf'))
+        if min_ > max_:
+            raise RangeError(f'invalid limits: {pname}_min > {pname}_max')
+        if value < min_:
+            raise RangeError(f'{pname} below {pname}_min')
+        if value > max_:
+            raise RangeError(f'{pname} above {pname}_max')
diff --git a/frappy/modules.py b/frappy/modules.py
index fc57d1d..850b06f 100644
--- a/frappy/modules.py
+++ b/frappy/modules.py
@@ -940,8 +940,12 @@ class Attached(Property):
     def __get__(self, obj, owner):
         if obj is None:
             return self
-        if self.name not in obj.attachedModules:
-            modobj = obj.DISPATCHER.get_module(super().__get__(obj, owner))
+        modobj = obj.attachedModules.get(self.name)
+        if not modobj:
+            modulename = super().__get__(obj, owner)
+            if not modulename:
+                return None  # happens when mandatory=False and modulename is not given
+            modobj = obj.secNode.get_module(modulename)
             if not isinstance(modobj, self.basecls):
                 raise ConfigError(f'attached module {self.name}={modobj.name!r} '\
                     f'must inherit from {self.basecls.__qualname__!r}')
diff --git a/frappy/persistent.py b/frappy/persistent.py
index 03e2499..3477801 100644
--- a/frappy/persistent.py
+++ b/frappy/persistent.py
@@ -78,7 +78,7 @@ class PersistentMixin(Module):
         super().__init__(name, logger, cfgdict, srv)
         persistentdir = os.path.join(generalConfig.logdir, 'persistent')
         os.makedirs(persistentdir, exist_ok=True)
-        self.persistentFile = os.path.join(persistentdir, f'{self.DISPATCHER.equipment_id}.{self.name}.json')
+        self.persistentFile = os.path.join(persistentdir, f'{self.secNode.equipment_id}.{self.name}.json')
         self.initData = {}  # "factory" settings
         loaded = self.loadPersistentData()
         for pname in self.parameters:
diff --git a/frappy/protocol/dispatcher.py b/frappy/protocol/dispatcher.py
index 1de1113..85f7449 100644
--- a/frappy/protocol/dispatcher.py
+++ b/frappy/protocol/dispatcher.py
@@ -18,6 +18,7 @@
 # Module authors:
 #   Enrico Faulhaber <enrico.faulhaber@frm2.tum.de>
 #   Markus Zolliker <markus.zolliker@psi.ch>
+#   Alexander Zaft <a.zaft@fz-juelich.de>
 #
 # *****************************************************************************
 """Dispatcher for SECoP Messages
@@ -29,28 +30,18 @@ Interface to the service offering part:
    on the connectionobj or on activated connections
  - 'add_connection(connectionobj)' registers new connection
  - 'remove_connection(connectionobj)' removes now longer functional connection
-
-Interface to the modules:
- - add_module(modulename, moduleobj, export=True) registers a new module under the
-   given name, may also register it for exporting (making accessible)
- - get_module(modulename) returns the requested module or None
- - remove_module(modulename_or_obj): removes the module (during shutdown)
-
 """
 
 import threading
-import traceback
-from collections import OrderedDict
 from time import time as currenttime
 
 from frappy.errors import NoSuchCommandError, NoSuchModuleError, \
-    NoSuchParameterError, ProtocolError, ReadOnlyError, ConfigError
+    NoSuchParameterError, ProtocolError, ReadOnlyError
 from frappy.params import Parameter
 from frappy.protocol.messages import COMMANDREPLY, DESCRIPTIONREPLY, \
     DISABLEEVENTSREPLY, ENABLEEVENTSREPLY, ERRORPREFIX, EVENTREPLY, \
-    HEARTBEATREPLY, IDENTREPLY, IDENTREQUEST, READREPLY, WRITEREPLY, \
-    LOGGING_REPLY, LOG_EVENT
-from frappy.lib import get_class
+    HEARTBEATREPLY, IDENTREPLY, IDENTREQUEST, LOG_EVENT, LOGGING_REPLY, \
+    READREPLY, WRITEREPLY
 
 
 def make_update(modulename, pobj):
@@ -71,10 +62,7 @@ class Dispatcher:
             self.nodeprops[k] = options.pop(k)
 
         self.log = logger
-        # map ALL modulename -> moduleobj
-        self._modules = {}
-        # list of EXPORTED modules
-        self._export = []
+        self.secnode = srv.secnode
         # list all connections
         self._connections = []
         # active (i.e. broadcast-receiving) connections
@@ -88,11 +76,6 @@ class Dispatcher:
         self.shutdown = srv.shutdown
         # handle to server
         self.srv = srv
-        # set of modules that failed creation
-        self.failed_modules = set()
-        # list of errors that occured during initialization
-        self.errors = []
-        self.traceback_counter = 0
 
     def broadcast_event(self, msg, reallyall=False):
         """broadcasts a msg to all active connections
@@ -148,163 +131,8 @@ class Dispatcher:
             self._connections.remove(conn)
         self.reset_connection(conn)
 
-    def register_module(self, moduleobj, modulename, export=True):
-        self.log.debug('registering module %r as %s (export=%r)',
-                       moduleobj, modulename, export)
-        self._modules[modulename] = moduleobj
-        if export:
-            self._export.append(modulename)
-
-    def get_module(self, modulename):
-        """ Returns a fully initialized module. Or None, if something went
-        wrong during instatiating/initializing the module."""
-        modobj = self.get_module_instance(modulename)
-        if modobj is None:
-            return None
-        if modobj._isinitialized:
-            return modobj
-
-        # also call earlyInit on the modules
-        self.log.debug('initializing module %r', modulename)
-        try:
-            modobj.earlyInit()
-            if not modobj.earlyInitDone:
-                self.errors.append(f'{modobj.earlyInit.__qualname__} was not called, probably missing super call')
-            modobj.initModule()
-            if not modobj.initModuleDone:
-                self.errors.append(f'{modobj.initModule.__qualname__} was not called, probably missing super call')
-        except Exception as e:
-            if self.traceback_counter == 0:
-                self.log.exception(traceback.format_exc())
-            self.traceback_counter += 1
-            self.errors.append(f'error initializing {modulename}: {e!r}')
-        modobj._isinitialized = True
-        self.log.debug('initialized module %r', modulename)
-        return modobj
-
-    def get_module_instance(self, modulename):
-        """ Returns the module in its current initialization state or creates a
-        new uninitialized modle to return.
-
-        When creating a new module, srv.module_config is accessed to get the
-        modules configuration.
-        """
-        if modulename in self._modules:
-            return self._modules[modulename]
-        if modulename in list(self._modules.values()):
-            # it's actually already the module object
-            return modulename
-        # create module from srv.module_cfg, store and return
-        self.log.debug('attempting to create module %r', modulename)
-
-        opts = self.srv.module_cfg.get(modulename, None)
-        if opts is None:
-            raise NoSuchModuleError(f'Module {modulename!r} does not exist on this SEC-Node!')
-        pymodule = None
-        try:  # pylint: disable=no-else-return
-            classname = opts.pop('cls')
-            if isinstance(classname, str):
-                pymodule = classname.rpartition('.')[0]
-                if pymodule in self.failed_modules:
-                    # creation has failed already once, do not try again
-                    return None
-                cls = get_class(classname)
-            else:
-                pymodule = classname.__module__
-                if pymodule in self.failed_modules:
-                    # creation has failed already once, do not try again
-                    return None
-                cls = classname
-        except Exception as e:
-            if str(e) == 'no such class':
-                self.errors.append(f'{classname} not found')
-            else:
-                self.failed_modules.add(pymodule)
-                if self.traceback_counter == 0:
-                    self.log.exception(traceback.format_exc())
-                self.traceback_counter += 1
-                self.errors.append(f'error importing {classname}')
-            return None
-        else:
-            try:
-                modobj = cls(modulename, self.log.getChild(modulename), opts, self.srv)
-            except ConfigError as e:
-                self.errors.append(f'error creating module {modulename}:')
-                for errtxt in e.args[0] if isinstance(e.args[0], list) else [e.args[0]]:
-                    self.errors.append('  ' + errtxt)
-                modobj = None
-            except Exception as e:
-                if self.traceback_counter == 0:
-                    self.log.exception(traceback.format_exc())
-                self.traceback_counter += 1
-                self.errors.append(f'error creating {modulename}')
-                modobj = None
-        if modobj:
-            self.register_module(modobj, modulename, modobj.export)
-            self.srv.modules[modulename] = modobj # IS HERE THE CORRECT PLACE?
-        return modobj
-
-    def remove_module(self, modulename_or_obj):
-        moduleobj = self.get_module(modulename_or_obj)
-        modulename = moduleobj.name
-        if modulename in self._export:
-            self._export.remove(modulename)
-        self._modules.pop(modulename)
-        self._subscriptions.pop(modulename, None)
-        for k in [kk for kk in self._subscriptions if kk.startswith(f'{modulename}:')]:
-            self._subscriptions.pop(k, None)
-
-    def list_module_names(self):
-        # return a copy of our list
-        return self._export[:]
-
-    def export_accessibles(self, modulename):
-        self.log.debug('export_accessibles(%r)', modulename)
-        if modulename in self._export:
-            # omit export=False params!
-            res = OrderedDict()
-            for aobj in self.get_module(modulename).accessibles.values():
-                if aobj.export:
-                    res[aobj.export] = aobj.for_export()
-            self.log.debug('list accessibles for module %s -> %r',
-                           modulename, res)
-            return res
-        self.log.debug('-> module is not to be exported!')
-        return OrderedDict()
-
-    def get_descriptive_data(self, specifier):
-        """returns a python object which upon serialisation results in the descriptive data"""
-        specifier = specifier or ''
-        modules = {}
-        result = {'modules': modules}
-        for modulename in self._export:
-            module = self.get_module(modulename)
-            if not module.export:
-                continue
-            # some of these need rework !
-            mod_desc = {'accessibles': self.export_accessibles(modulename)}
-            mod_desc.update(module.exportProperties())
-            mod_desc.pop('export', False)
-            modules[modulename] = mod_desc
-        modname, _, pname = specifier.partition(':')
-        if modname in modules:  # extension to SECoP standard: description of a single module
-            result = modules[modname]
-            if pname in result['accessibles']:  # extension to SECoP standard: description of a single accessible
-                # command is also accepted
-                result = result['accessibles'][pname]
-            elif pname:
-                raise NoSuchParameterError(f'Module {modname!r} has no parameter {pname!r}')
-        elif not modname or modname == '.':
-            result['equipment_id'] = self.equipment_id
-            result['firmware'] = 'FRAPPY - The Python Framework for SECoP'
-            result['version'] = '2021.02'
-            result.update(self.nodeprops)
-        else:
-            raise NoSuchModuleError(f'Module {modname!r} does not exist')
-        return result
-
     def _execute_command(self, modulename, exportedname, argument=None):
-        moduleobj = self.get_module(modulename)
+        moduleobj = self.secnode.get_module(modulename)
         if moduleobj is None:
             raise NoSuchModuleError(f'Module {modulename!r} does not exist')
 
@@ -323,7 +151,7 @@ class Dispatcher:
         return result, {'t': currenttime()}
 
     def _setParameterValue(self, modulename, exportedname, value):
-        moduleobj = self.get_module(modulename)
+        moduleobj = self.secnode.get_module(modulename)
         if moduleobj is None:
             raise NoSuchModuleError(f'Module {modulename!r} does not exist')
 
@@ -344,7 +172,7 @@ class Dispatcher:
         return pobj.export_value(), {'t': pobj.timestamp} if pobj.timestamp else {}
 
     def _getParameterValue(self, modulename, exportedname):
-        moduleobj = self.get_module(modulename)
+        moduleobj = self.secnode.get_module(modulename)
         if moduleobj is None:
             raise NoSuchModuleError(f'Module {modulename!r} does not exist')
 
@@ -401,7 +229,7 @@ class Dispatcher:
         return (IDENTREPLY, None, None)
 
     def handle_describe(self, conn, specifier, data):
-        return (DESCRIPTIONREPLY, specifier or '.', self.get_descriptive_data(specifier))
+        return (DESCRIPTIONREPLY, specifier or '.', self.secnode.get_descriptive_data(specifier))
 
     def handle_read(self, conn, specifier, data):
         if data:
@@ -440,9 +268,9 @@ class Dispatcher:
             modulename, exportedname = specifier, None
             if ':' in specifier:
                 modulename, exportedname = specifier.split(':', 1)
-            if modulename not in self._export:
+            if modulename not in self.secnode.export:
                 raise NoSuchModuleError(f'Module {modulename!r} does not exist')
-            moduleobj = self.get_module(modulename)
+            moduleobj = self.secnode.get_module(modulename)
             if exportedname is not None:
                 pname = moduleobj.accessiblename2attr.get(exportedname, True)
                 if pname and pname not in moduleobj.accessibles:
@@ -456,12 +284,12 @@ class Dispatcher:
         else:
             # activate all modules
             self._active_connections.add(conn)
-            modules = [(m, None) for m in self._export]
+            modules = [(m, None) for m in self.secnode.export]
 
         # send updates for all subscribed values.
         # note: The initial poll already happend before the server is active
         for modulename, pname in modules:
-            moduleobj = self._modules.get(modulename, None)
+            moduleobj = self.secnode.modules.get(modulename, None)
             if pname:
                 conn.send_reply(make_update(modulename, moduleobj.parameters[pname]))
                 continue
@@ -485,16 +313,16 @@ class Dispatcher:
         conn.send_reply((LOG_EVENT, f'{modname}:{level}', msg))
 
     def set_all_log_levels(self, conn, level):
-        for modobj in self._modules.values():
-            modobj.setRemoteLogging(conn, level)
+        for modobj in self.secnode.modules.values():
+            modobj.setRemoteLogging(conn, level, self.send_log_msg)
 
     def handle_logging(self, conn, specifier, level):
         if specifier == '#':
             self.log.handlers[1].setLevel(int(level))
             return LOGGING_REPLY, specifier, level
         if specifier and specifier != '.':
-            modobj = self._modules[specifier]
-            modobj.setRemoteLogging(conn, level)
+            modobj = self.secnode.modules[specifier]
+            modobj.setRemoteLogging(conn, level, self.send_log_msg)
         else:
             self.set_all_log_levels(conn, level)
         return LOGGING_REPLY, specifier, level
diff --git a/frappy/secnode.py b/frappy/secnode.py
new file mode 100644
index 0000000..6b7b91a
--- /dev/null
+++ b/frappy/secnode.py
@@ -0,0 +1,281 @@
+# *****************************************************************************
+#
+# This program is free software; you can redistribute it and/or modify it under
+# the terms of the GNU General Public License as published by the Free Software
+# Foundation; either version 2 of the License, or (at your option) any later
+# version.
+#
+# This program is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+# FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+# details.
+#
+# You should have received a copy of the GNU General Public License along with
+# this program; if not, write to the Free Software Foundation, Inc.,
+# 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+#
+# Module authors:
+#   Alexander Zaft <a.zaft@fz-juelich.de>
+#
+# *****************************************************************************
+
+import traceback
+from collections import OrderedDict
+
+from frappy.dynamic import Pinata
+from frappy.errors import ConfigError, NoSuchModuleError, NoSuchParameterError
+from frappy.lib import get_class
+
+
+class SecNode:
+    """Managing the modules.
+
+    Interface to the modules:
+     - add_module(module, modulename)
+     - get_module(modulename) returns the requested module or None if there is
+       no suitable configuration on the server
+    """
+    def __init__(self, name, logger, options, srv):
+        self.equipment_id = options.pop('equipment_id', name)
+        self.nodeprops = {}
+        for k in list(options):
+            self.nodeprops[k] = options.pop(k)
+        # map ALL modulename -> moduleobj
+        self.modules = {}
+        # list of EXPORTED modules
+        self.export = []
+        self.log = logger
+        self.srv = srv
+        # set of modules that failed creation
+        self.failed_modules = set()
+        # list of errors that occured during initialization
+        self.errors = []
+        self.traceback_counter = 0
+        self.name = name
+
+    def get_module(self, modulename):
+        """ Returns a fully initialized module. Or None, if something went
+        wrong during instatiating/initializing the module."""
+        modobj = self.get_module_instance(modulename)
+        if modobj is None:
+            return None
+        if modobj._isinitialized:
+            return modobj
+
+        # also call earlyInit on the modules
+        self.log.debug('initializing module %r', modulename)
+        try:
+            modobj.earlyInit()
+            if not modobj.earlyInitDone:
+                self.errors.append(f'{modobj.earlyInit.__qualname__} was not '
+                                   f'called, probably missing super call')
+            modobj.initModule()
+            if not modobj.initModuleDone:
+                self.errors.append(f'{modobj.initModule.__qualname__} was not '
+                                   f'called, probably missing super call')
+        except Exception as e:
+            if self.traceback_counter == 0:
+                self.log.exception(traceback.format_exc())
+            self.traceback_counter += 1
+            self.errors.append(f'error initializing {modulename}: {e!r}')
+        modobj._isinitialized = True
+        self.log.debug('initialized module %r', modulename)
+        return modobj
+
+    def get_module_instance(self, modulename):
+        """ Returns the module in its current initialization state or creates a
+        new uninitialized modle to return.
+
+        When creating a new module, srv.module_config is accessed to get the
+        modules configuration.
+        """
+        if modulename in self.modules:
+            return self.modules[modulename]
+        if modulename in list(self.modules.values()):
+            # it's actually already the module object
+            return modulename
+        # create module from srv.module_cfg, store and return
+        self.log.debug('attempting to create module %r', modulename)
+
+        opts = self.srv.module_cfg.get(modulename, None)
+        if opts is None:
+            raise NoSuchModuleError(f'Module {modulename!r} does not exist on '
+                                    f'this SEC-Node!')
+        pymodule = None
+        try:  # pylint: disable=no-else-return
+            classname = opts.pop('cls')
+            if isinstance(classname, str):
+                pymodule = classname.rpartition('.')[0]
+                if pymodule in self.failed_modules:
+                    # creation has failed already once, do not try again
+                    return None
+                cls = get_class(classname)
+            else:
+                pymodule = classname.__module__
+                if pymodule in self.failed_modules:
+                    # creation has failed already once, do not try again
+                    return None
+                cls = classname
+        except Exception as e:
+            if str(e) == 'no such class':
+                self.errors.append(f'{classname} not found')
+            else:
+                self.failed_modules.add(pymodule)
+                if self.traceback_counter == 0:
+                    self.log.exception(traceback.format_exc())
+                self.traceback_counter += 1
+                self.errors.append(f'error importing {classname}')
+            return None
+        else:
+            try:
+                modobj = cls(modulename, self.log.parent.getChild(modulename),
+                             opts, self.srv)
+            except ConfigError as e:
+                self.errors.append(f'error creating module {modulename}:')
+                for errtxt in e.args[0] if isinstance(e.args[0], list) else [e.args[0]]:
+                    self.errors.append('  ' + errtxt)
+                modobj = None
+            except Exception as e:
+                if self.traceback_counter == 0:
+                    self.log.exception(traceback.format_exc())
+                self.traceback_counter += 1
+                self.errors.append(f'error creating {modulename}')
+                modobj = None
+        if modobj:
+            self.add_module(modobj, modulename)
+        return modobj
+
+    def create_modules(self):
+        self.modules = OrderedDict()
+
+        # create and initialize modules
+        todos = list(self.srv.module_cfg.items())
+        while todos:
+            modname, options = todos.pop(0)
+            if modname in self.modules:
+                # already created via Attached
+                continue
+            # For Pinata modules: we need to access this in Self.get_module
+            self.srv.module_cfg[modname] = dict(options)
+            modobj = self.get_module_instance(modname)  # lazy
+            if modobj is None:
+                self.log.debug('Module %s returned None', modname)
+                continue
+            self.modules[modname] = modobj
+            if isinstance(modobj, Pinata):
+                # scan for dynamic devices
+                pinata = self.get_module(modname)
+                pinata_modules = list(pinata.scanModules())
+                for name, _cfg in pinata_modules:
+                    if name in self.srv.module_cfg:
+                        self.log.error('Module %s, from pinata %s, already '
+                                       'exists in config file!', name, modname)
+                self.log.info('Pinata %s found %d modules',
+                              modname, len(pinata_modules))
+                todos.extend(pinata_modules)
+
+    def export_accessibles(self, modulename):
+        self.log.debug('export_accessibles(%r)', modulename)
+        if modulename in self.export:
+            # omit export=False params!
+            res = OrderedDict()
+            for aobj in self.get_module(modulename).accessibles.values():
+                if aobj.export:
+                    res[aobj.export] = aobj.for_export()
+            self.log.debug('list accessibles for module %s -> %r',
+                           modulename, res)
+            return res
+        self.log.debug('-> module is not to be exported!')
+        return OrderedDict()
+
+    def get_descriptive_data(self, specifier):
+        """returns a python object which upon serialisation results in the
+        descriptive data"""
+        specifier = specifier or ''
+        modules = {}
+        result = {'modules': modules}
+        for modulename in self.export:
+            module = self.get_module(modulename)
+            if not module.export:
+                continue
+            # some of these need rework !
+            mod_desc = {'accessibles': self.export_accessibles(modulename)}
+            mod_desc.update(module.exportProperties())
+            mod_desc.pop('export', False)
+            modules[modulename] = mod_desc
+        modname, _, pname = specifier.partition(':')
+        if modname in modules:  # extension to SECoP standard: description of a single module
+            result = modules[modname]
+            if pname in result['accessibles']:  # extension to SECoP standard: description of a single accessible
+                # command is also accepted
+                result = result['accessibles'][pname]
+            elif pname:
+                raise NoSuchParameterError(f'Module {modname!r} '
+                                           f'has no parameter {pname!r}')
+        elif not modname or modname == '.':
+            result['equipment_id'] = self.equipment_id
+            result['firmware'] = 'FRAPPY - The Python Framework for SECoP'
+            result['version'] = '2021.02'
+            result.update(self.nodeprops)
+        else:
+            raise NoSuchModuleError(f'Module {modname!r} does not exist')
+        return result
+
+    def add_module(self, module, modulename):
+        """Adds a named module object to this SecNode."""
+        self.modules[modulename] = module
+        if module.export:
+            self.export.append(modulename)
+
+    # def remove_module(self, modulename_or_obj):
+    #     moduleobj = self.get_module(modulename_or_obj)
+    #     modulename = moduleobj.name
+    #     if modulename in self.export:
+    #         self.export.remove(modulename)
+    #     self.modules.pop(modulename)
+    #     self._subscriptions.pop(modulename, None)
+    #     for k in [kk for kk in self._subscriptions if kk.startswith(f'{modulename}:')]:
+    #         self._subscriptions.pop(k, None)
+
+    def shutdown_modules(self):
+        """Call 'shutdownModule' for all modules."""
+        for name in self._getSortedModules():
+            self.modules[name].shutdownModule()
+
+    def _getSortedModules(self):
+        """Sort modules topologically by inverse dependency.
+
+        Example: if there is an IO device A and module B depends on it, then
+        the result will be [B, A].
+        Right now, if the dependency graph is not a DAG, we give up and return
+        the unvisited nodes to be dismantled at the end.
+        Taken from Introduction to Algorithms [CLRS].
+        """
+        def go(name):
+            if name in done:  # visiting a node
+                return True
+            if name in visited:
+                visited.add(name)
+                return False  # cycle in dependencies -> fail
+            visited.add(name)
+            if name in unmarked:
+                unmarked.remove(name)
+            for module in self.modules[name].attachedModules.values():
+                res = go(module.name)
+                if not res:
+                    return False
+            visited.remove(name)
+            done.add(name)
+            l.append(name)
+            return True
+
+        unmarked = set(self.modules.keys())  # unvisited nodes
+        visited = set()  # visited in DFS, but not completed
+        done = set()
+        l = []  # list of sorted modules
+
+        while unmarked:
+            if not go(unmarked.pop()):
+                self.log.error('cyclical dependency between modules!')
+                return l[::-1] + list(visited) + list(unmarked)
+        return l[::-1]
diff --git a/frappy/server.py b/frappy/server.py
index 5152728..36aea2a 100644
--- a/frappy/server.py
+++ b/frappy/server.py
@@ -25,14 +25,13 @@
 import os
 import signal
 import sys
-from collections import OrderedDict
 
 from frappy.config import load_config
 from frappy.errors import ConfigError
-from frappy.dynamic import Pinata
 from frappy.lib import formatException, generalConfig, get_class, mkthread
 from frappy.lib.multievent import MultiEvent
 from frappy.params import PREDEFINED_ACCESSIBLES
+from frappy.secnode import SecNode
 
 try:
     from daemon import DaemonContext
@@ -171,14 +170,13 @@ class Server:
                 # server_close() called by 'with'
 
             self.log.info(f'stopped listenning, cleaning up'
-                          f' {len(self.modules)} modules')
+                          f' {len(self.secnode.modules)} modules')
             # if systemd:
             #     if self._restart:
             #         systemd.daemon.notify('RELOADING=1')
             #     else:
             #         systemd.daemon.notify('STOPPING=1')
-            for name in self._getSortedModules():
-                self.modules[name].shutdownModule()
+            self.secnode.shutdown_modules()
             if self._restart:
                 self.restart_hook()
                 self.log.info('restarting')
@@ -205,50 +203,27 @@ class Server:
         errors = []
         opts = dict(self.node_cfg)
         cls = get_class(opts.pop('cls'))
-        self.dispatcher = cls(opts.pop('name', self._cfgfiles),
-                              self.log.getChild('dispatcher'), opts, self)
+        name = opts.pop('name', self._cfgfiles)
+        # TODO: opts not in both
+        self.secnode = SecNode(name, self.log.getChild('secnode'), opts, self)
+        self.dispatcher = cls(name, self.log.getChild('dispatcher'), opts, self)
 
         if opts:
-            self.dispatcher.errors.append(self.unknown_options(cls, opts))
-        self.modules = OrderedDict()
-
-        # create and initialize modules
-        todos = list(self.module_cfg.items())
-        while todos:
-            modname, options = todos.pop(0)
-            if modname in self.modules:
-                # already created by Dispatcher (via Attached)
-                continue
-            # For Pinata modules: we need to access this in Dispatcher.get_module
-            self.module_cfg[modname] = dict(options)
-            modobj = self.dispatcher.get_module_instance(modname) # lazy
-            if modobj is None:
-                self.log.debug('Module %s returned None', modname)
-                continue
-            self.modules[modname] = modobj
-            if isinstance(modobj, Pinata):
-                # scan for dynamic devices
-                pinata = self.dispatcher.get_module(modname)
-                pinata_modules = list(pinata.scanModules())
-                for name, _cfg in pinata_modules:
-                    if name in self.module_cfg:
-                        self.log.error('Module %s, from pinata %s, already'
-                                       ' exists in config file!', name, modname)
-                self.log.info('Pinata %s found %d modules', modname, len(pinata_modules))
-                todos.extend(pinata_modules)
+            self.secnode.errors.append(self.unknown_options(cls, opts))
 
+        self.secnode.create_modules()
         # initialize all modules by getting them with Dispatcher.get_module,
         # which is done in the get_descriptive data
         # TODO: caching, to not make this extra work
-        self.dispatcher.get_descriptive_data('')
+        self.secnode.get_descriptive_data('')
         # =========== All modules are initialized ===========
 
         # all errors from initialization process
-        errors = self.dispatcher.errors
+        errors = self.secnode.errors
 
         if not self._testonly:
             start_events = MultiEvent(default_timeout=30)
-            for modname, modobj in self.modules.items():
+            for modname, modobj in self.secnode.modules.items():
                 # startModule must return either a timeout value or None (default 30 sec)
                 start_events.name = f'module {modname}'
                 modobj.startModule(start_events)
@@ -275,7 +250,8 @@ class Server:
         self.log.info('all modules started')
         history_path = os.environ.get('FRAPPY_HISTORY')
         if history_path:
-            from frappy_psi.historywriter import FrappyHistoryWriter  # pylint: disable=import-outside-toplevel
+            from frappy_psi.historywriter import \
+                FrappyHistoryWriter  # pylint: disable=import-outside-toplevel
             writer = FrappyHistoryWriter(history_path, PREDEFINED_ACCESSIBLES.keys(), self.dispatcher)
             # treat writer as a connection
             self.dispatcher.add_connection(writer)
@@ -288,41 +264,3 @@ class Server:
         #   history_path = os.environ.get('ALTERNATIVE_HISTORY')
         #   if history_path:
         #       from frappy_<xx>.historywriter import ... etc.
-
-    def _getSortedModules(self):
-        """Sort modules topologically by inverse dependency.
-
-        Example: if there is an IO device A and module B depends on it, then
-        the result will be [B, A].
-        Right now, if the dependency graph is not a DAG, we give up and return
-        the unvisited nodes to be dismantled at the end.
-        Taken from Introduction to Algorithms [CLRS].
-        """
-        def go(name):
-            if name in done:  # visiting a node
-                return True
-            if name in visited:
-                visited.add(name)
-                return False  # cycle in dependencies -> fail
-            visited.add(name)
-            if name in unmarked:
-                unmarked.remove(name)
-            for module in self.modules[name].attachedModules.values():
-                res = go(module.name)
-                if not res:
-                    return False
-            visited.remove(name)
-            done.add(name)
-            l.append(name)
-            return True
-
-        unmarked = set(self.modules.keys())  # unvisited nodes
-        visited = set()  # visited in DFS, but not completed
-        done = set()
-        l = []  # list of sorted modules
-
-        while unmarked:
-            if not go(unmarked.pop()):
-                self.log.error('cyclical dependency between modules!')
-                return l[::-1] + list(visited) + list(unmarked)
-        return l[::-1]
diff --git a/frappy_psi/sea.py b/frappy_psi/sea.py
index 4554c22..6d4cf4c 100644
--- a/frappy_psi/sea.py
+++ b/frappy_psi/sea.py
@@ -252,7 +252,7 @@ class SeaClient(ProxyClient, Module):
                 if result == '1':
                     self.asynio.writeline(('get_all_param ' + ' '.join(self.objects)).encode())
                 else:
-                    self.DISPATCHER.shutdown()
+                    self.secNode.srv.shutdown()
             try:
                 reply = self.asynio.readline()
                 if reply is None:
@@ -316,7 +316,7 @@ class SeaClient(ProxyClient, Module):
                         if path == '/device/changetime':
                             recheck = time.time() + 1
                         elif path.startswith('/device/frappy_%s' % self.service) and value == '':
-                            self.DISPATCHER.shutdown()
+                            self.secNode.srv.shutdown()
                 else:
                     for module, param in mplist:
                         oldv, oldt, oldr = self.cache.get((module, param), [None, None, None])
@@ -659,7 +659,7 @@ class SeaModule(Module):
                 readerror = secop_error(e)
         pobj.readerror = readerror
         if pobj.export:
-            self.DISPATCHER.broadcast_event(make_update(self.name, pobj))
+            self.secNode.srv.dispatcher.broadcast_event(make_update(self.name, pobj))
 
     def initModule(self):
         self.io.register_obj(self, self.sea_object)
diff --git a/test/test_attach.py b/test/test_attach.py
index 6b6c251..de41e35 100644
--- a/test/test_attach.py
+++ b/test/test_attach.py
@@ -57,11 +57,23 @@ class LoggerStub:
 logger = LoggerStub()
 
 
+class SecNodeStub:
+    def __init__(self):
+        self.modules = {}
+
+    def add_module(self, module, modname):
+        self.modules[modname] = module
+
+    def get_module(self, modname):
+        return self.modules[modname]
+
+
 class ServerStub:
     restart = None
     shutdown = None
 
     def __init__(self):
+        self.secnode = SecNodeStub()
         self.dispatcher = Dispatcher('dispatcher', logger, {}, self)
 
 
@@ -73,6 +85,6 @@ def test_attach():
     a = Module('a', logger, {'description': ''}, srv)
     m = Mod('m', logger, {'description': '', 'att': 'a'}, srv)
     assert m.propertyValues['att'] == 'a'
-    srv.dispatcher.register_module(a, 'a')
-    srv.dispatcher.register_module(m, 'm')
+    srv.secnode.add_module(a, 'a')
+    srv.secnode.add_module(m, 'm')
     assert m.att == a
diff --git a/test/test_handler.py b/test/test_handler.py
index 2215673..2e738fd 100644
--- a/test/test_handler.py
+++ b/test/test_handler.py
@@ -58,6 +58,7 @@ logger = LoggerStub()
 class ServerStub:
     def __init__(self, updates):
         self.dispatcher = DispatcherStub(updates)
+        self.secnode = None
 
 
 class ModuleTest(Module):
diff --git a/test/test_logging.py b/test/test_logging.py
index bd1af39..d6a9428 100644
--- a/test/test_logging.py
+++ b/test/test_logging.py
@@ -29,11 +29,24 @@ import frappy.logging
 from frappy.logging import logger, generalConfig, HasComlog
 
 
+class SecNodeStub:
+    def __init__(self):
+        self.modules = {}
+        self.name = ""
+
+    def add_module(self, module, modname):
+        self.modules[modname] = module
+
+    def get_module(self, modname):
+        return self.modules[modname]
+
+
 class ServerStub:
     restart = None
     shutdown = None
 
     def __init__(self):
+        self.secnode = SecNodeStub()
         self.dispatcher = Dispatcher('', logger.log.getChild('dispatcher'), {}, self)
 
 
@@ -98,7 +111,7 @@ def init_(monkeypatch):
                 def __init__(self, name, srv, **kwds):
                     kwds['description'] = ''
                     super().__init__(name or 'mod', logger.log.getChild(name), kwds, srv)
-                    srv.dispatcher.register_module(self, name, name)
+                    srv.secnode.add_module(self, name)
                     self.result[:] = []
 
                 def earlyInit(self):
diff --git a/test/test_modules.py b/test/test_modules.py
index 7da7853..e1d8313 100644
--- a/test/test_modules.py
+++ b/test/test_modules.py
@@ -65,6 +65,7 @@ logger = LoggerStub()
 class ServerStub:
     def __init__(self, updates):
         self.dispatcher = DispatcherStub(updates)
+        self.secnode = None
 
 
 class DummyMultiEvent(threading.Event):
@@ -712,6 +713,7 @@ def test_super_call():
     class ServerStub1:
         def __init__(self, updates):
             self.dispatcher = DispatcherStub1(updates)
+            self.secnode = None
 
     updates = []
     srv = ServerStub1(updates)
diff --git a/test/test_persistent.py b/test/test_persistent.py
index 2d58d4b..5823b45 100644
--- a/test/test_persistent.py
+++ b/test/test_persistent.py
@@ -30,6 +30,10 @@ from frappy.lib import generalConfig
 from frappy.persistent import PersistentParam, PersistentMixin
 
 
+class SecNodeStub:
+    pass
+
+
 class DispatcherStub:
     def announce_update(self, modulename, pname, pobj):
         pass
@@ -48,7 +52,8 @@ logger = LoggerStub()
 class ServerStub:
     def __init__(self, equipment_id):
         self.dispatcher = DispatcherStub()
-        self.dispatcher.equipment_id = equipment_id
+        self.secnode = SecNodeStub()
+        self.secnode.equipment_id = equipment_id
 
 
 class Mod(PersistentMixin, Module):
diff --git a/test/test_poller.py b/test/test_poller.py
index b47d38e..13ef74d 100644
--- a/test/test_poller.py
+++ b/test/test_poller.py
@@ -69,6 +69,7 @@ class ServerStub:
     def __init__(self):
         generalConfig.testinit()
         self.dispatcher = DispatcherStub()
+        self.secnode = None
 
 
 class Base(Module):
diff --git a/test/test_statemachine.py b/test/test_statemachine.py
index 2a49021..978d2cf 100644
--- a/test/test_statemachine.py
+++ b/test/test_statemachine.py
@@ -206,6 +206,7 @@ class DispatcherStub:
 class ServerStub:
     def __init__(self, updates):
         self.dispatcher = DispatcherStub(updates)
+        self.secnode = None
 
 
 class Mod(HasStates, Drivable):