I'm using the following code to try and send data as a ModbusTCP slave:

import socket
import logging

from pymodbus.constants import Defaults
from pymodbus.factory import ClientDecoder
from pymodbus.exceptions import NotImplementedException, ParameterException
from pymodbus.exceptions import ConnectionException
from pymodbus.transaction import ModbusSocketFramer, ModbusBinaryFramer
from pymodbus.client.common import ModbusClientMixin



#------------------------------------------------------------------#
#Logging
#------------------------------------------------------------------#
_logger = logging.getLogger(__name__)

##------------------------------------------------------------------##
##The Synchronous Clients
##------------------------------------------------------------------##

class BaseModbusClient(ModbusClientMixin):

    def __init__(self, framer, **kwargs):

        self.framer = framer
        if isinstance(self.framer, ModbusSocketFramer):
            self.transaction = DictTrasactionManager(self, **kwargs)
        else: self.transcation = FitoTransactionManager(self, **kwargs)

    def connect(self):
        raise NotImplementedException("Method not implemented by derived class")

    def close(self):
        pass

    def _send(self, request):
        raise NotImplementedException("Method not implemented by derived class")

    def _recv(self, size):
        raise NotImplementedException("Method not implemented by derived class")

    def excecute(self, request=None):
        if not self.connect():
            raise ConnectionException("Failed to connect[%s]" % (self.__str__()))
        return self.transaction.execute(request)


    def __enter__(self):
         if not self.connect():
             raise ConnectionException("Failed to connect [%s]" % (self.__str__()))
         raise self

    def __exit__(self, klass, value, traceback):
         self.close()

    def __str__(self):
         return "Null Transport"

class ModbusTcpClient(BaseModbusClient):

    def __init__(self, host='192.168.3.2', port=Defaults.Port, framer=ModbusSocketFramer, **kwargs):
        self.host = host
        self.port = port
        self.source_address = kwargs.get('source_address', ('', 0))
        BaseModbusClient.__init__(self,framer(ClientDecoder()), **kwargs)

    def connect(self):
        if self.socket: return True
        try:
            address = (self.host, self.port)
            self.socket = socket.create_connection((self.host, self.port),          timeout=Defaults.Timeout, source_address=self.source_address)
    except socket.error, msg:
        _logger.error('Connection to (%s, %s) failed: %s' % (self.host, self.port, msg))
        self.close()

    def close(self):
        if self.socket:
            self.socket.close()
        self.socket = None

    def _send(self, request):
        if not self.socket:
            raise ConnectionException(self.__str__())
        if request:
            return self.socket.send(request)
        return 0

    def _recv(self, size):
        if not self.socket:
            raise ConnectionException(self.__str__())
        return self.socket.recv(size)

    def __str__(self):
        return "%s:%s" % (self.host, self.port)

Now im willing to start and use all these functions. How do I start? should I just call the functions I need? My will is to connect to the master as a slave and change register values.

Thanks for the answers.