Asynchronous Client Example

#!/usr/bin/env python
"""
Pymodbus Asynchronous Client Examples
--------------------------------------------------------------------------

The following is an example of how to use the asynchronous modbus
client implementation from pymodbus.
"""
# --------------------------------------------------------------------------- # 
# import needed libraries
# --------------------------------------------------------------------------- # 
from twisted.internet import reactor, protocol
from pymodbus.constants import Defaults

# --------------------------------------------------------------------------- # 
# choose the requested modbus protocol
# --------------------------------------------------------------------------- # 
from pymodbus.client.async import ModbusClientProtocol
#from pymodbus.client.async import ModbusUdpClientProtocol

# --------------------------------------------------------------------------- # 
# configure the client logging
# --------------------------------------------------------------------------- # 
import logging
logging.basicConfig()
log = logging.getLogger()
log.setLevel(logging.DEBUG)

# --------------------------------------------------------------------------- # 
# helper method to test deferred callbacks
# --------------------------------------------------------------------------- #


def dassert(deferred, callback):
    def _assertor(value):
        assert value

    deferred.addCallback(lambda r: _assertor(callback(r)))
    deferred.addErrback(lambda _: _assertor(False))

# --------------------------------------------------------------------------- # 
# specify slave to query
# --------------------------------------------------------------------------- # 
# The slave to query is specified in an optional parameter for each
# individual request. This can be done by specifying the `unit` parameter
# which defaults to `0x00`
# --------------------------------------------------------------------------- #


def exampleRequests(client):
    rr = client.read_coils(1, 1, unit=0x02)

# --------------------------------------------------------------------------- # 
# example requests
# --------------------------------------------------------------------------- # 
# simply call the methods that you would like to use. An example session
# is displayed below along with some assert checks. Note that unlike the
# synchronous version of the client, the asynchronous version returns
# deferreds which can be thought of as a handle to the callback to send
# the result of the operation.  We are handling the result using the
# deferred assert helper(dassert).
# --------------------------------------------------------------------------- #

UNIT = 0x01

def beginAsynchronousTest(client):
    rq = client.write_coil(1, True, unit=UNIT)
    rr = client.read_coils(1, 1, unit=UNIT)
    dassert(rq, lambda r: r.function_code < 0x80)     # test for no error
    dassert(rr, lambda r: r.bits[0] == True)          # test the expected value
    
    rq = client.write_coils(1, [True]*8, unit=UNIT)
    rr = client.read_coils(1, 8, unit=UNIT)
    dassert(rq, lambda r: r.function_code < 0x80)     # test for no error
    dassert(rr, lambda r: r.bits == [True]*8)        # test the expected value
    
    rq = client.write_coils(1, [False]*8, unit=UNIT)
    rr = client.read_discrete_inputs(1, 8, unit=UNIT)
    dassert(rq, lambda r: r.function_code < 0x80)     # test for no error
    dassert(rr, lambda r: r.bits == [True]*8)        # test the expected value
    
    rq = client.write_register(1, 10, unit=UNIT)
    rr = client.read_holding_registers(1, 1, unit=UNIT)
    dassert(rq, lambda r: r.function_code < 0x80)     # test for no error
    dassert(rr, lambda r: r.registers[0] == 10)       # test the expected value
    
    rq = client.write_registers(1, [10]*8, unit=UNIT)
    rr = client.read_input_registers(1, 8, unit=UNIT)
    dassert(rq, lambda r: r.function_code < 0x80)     # test for no error
    dassert(rr, lambda r: r.registers == [17]*8)      # test the expected value
    
    arguments = {
        'read_address':    1,
        'read_count':      8,
        'write_address':   1,
        'write_registers': [20]*8,
    }
    rq = client.readwrite_registers(**arguments, unit=UNIT)
    rr = client.read_input_registers(1, 8, unit=UNIT)
    dassert(rq, lambda r: r.registers == [20]*8)      # test the expected value
    dassert(rr, lambda r: r.registers == [17]*8)      # test the expected value

    # ----------------------------------------------------------------------- #
    # close the client at some time later
    # ----------------------------------------------------------------------- #
    reactor.callLater(1, client.transport.loseConnection)
    reactor.callLater(2, reactor.stop)

# --------------------------------------------------------------------------- # 
# extra requests
# --------------------------------------------------------------------------- # 
# If you are performing a request that is not available in the client
# mixin, you have to perform the request like this instead::
#
# from pymodbus.diag_message import ClearCountersRequest
# from pymodbus.diag_message import ClearCountersResponse
#
# request  = ClearCountersRequest()
# response = client.execute(request)
# if isinstance(response, ClearCountersResponse):
#     ... do something with the response
#
# --------------------------------------------------------------------------- # 

# --------------------------------------------------------------------------- # 
# choose the client you want
# --------------------------------------------------------------------------- # 
# make sure to start an implementation to hit against. For this
# you can use an existing device, the reference implementation in the tools
# directory, or start a pymodbus server.
# --------------------------------------------------------------------------- #


if __name__ == "__main__":
    defer = protocol.ClientCreator(
        reactor, ModbusClientProtocol).connectTCP("localhost", 5020)
    defer.addCallback(beginAsynchronousTest)
    reactor.run()