commit 3ebeaf7b0b82485ed9867ac8e9bd0c2d1cc7e122
Author: Patrick McDonagh <pmcdonagh@henry-pump.com>
Date:   Mon Oct 31 17:02:21 2016 -0500

    Sample Modbus TCP server code

diff --git a/poc-to-modbus.py b/poc-to-modbus.py
new file mode 100644
index 0000000..46a35d7
--- /dev/null
+++ b/poc-to-modbus.py
@@ -0,0 +1,85 @@
+#!/usr/bin/env python3
+'''
+Pymodbus Server With Updating Thread
+--------------------------------------------------------------------------
+
+This is an example of having a background thread updating the
+context while the server is operating. This can also be done with
+a python thread::
+
+    from threading import Thread
+
+    thread = Thread(target=updating_writer, args=(context,))
+    thread.start()
+'''
+# ---------------------------------------------------------------------------#
+# import the modbus libraries we need
+# ---------------------------------------------------------------------------#
+from pymodbus.server.async import StartTcpServer
+from pymodbus.device import ModbusDeviceIdentification
+from pymodbus.datastore import ModbusSequentialDataBlock
+from pymodbus.datastore import ModbusSlaveContext, ModbusServerContext
+# from pymodbus.transaction import ModbusRtuFramer, ModbusAsciiFramer
+
+# ---------------------------------------------------------------------------#
+# import the twisted libraries we need
+# ---------------------------------------------------------------------------#
+from twisted.internet.task import LoopingCall
+
+# ---------------------------------------------------------------------------#
+# configure the service logging
+# ---------------------------------------------------------------------------#
+import logging
+logging.basicConfig()
+log = logging.getLogger()
+log.setLevel(logging.DEBUG)
+
+
+# ---------------------------------------------------------------------------#
+# define your callback process
+# ---------------------------------------------------------------------------#
+def updating_writer(a):
+    ''' A worker process that runs every so often and
+    updates live values of the context. It should be noted
+    that there is a race condition for the update.
+
+    :param arguments: The input arguments to the call
+    '''
+    log.debug("updating the context")
+    context = a[0]
+    register = 3
+    slave_id = 0x00
+    address = 0x10
+    values = context[slave_id].getValues(register, address, count=5)
+    values = [v + 1 for v in values]
+    log.debug("new values: " + str(values))
+    context[slave_id].setValues(register, address, values)
+
+# ---------------------------------------------------------------------------#
+# initialize your data store
+# ---------------------------------------------------------------------------#
+store = ModbusSlaveContext(
+    di=ModbusSequentialDataBlock(0, [17]*100),
+    co=ModbusSequentialDataBlock(0, [17]*100),
+    hr=ModbusSequentialDataBlock(0, [17]*100),
+    ir=ModbusSequentialDataBlock(0, [17]*100))
+context = ModbusServerContext(slaves=store, single=True)
+
+# ---------------------------------------------------------------------------#
+# initialize the server information
+# ---------------------------------------------------------------------------#
+identity = ModbusDeviceIdentification()
+identity.VendorName = 'pymodbus'
+identity.ProductCode = 'PM'
+identity.VendorUrl = 'http://github.com/bashwork/pymodbus/'
+identity.ProductName = 'pymodbus Server'
+identity.ModelName = 'pymodbus Server'
+identity.MajorMinorRevision = '1.0'
+
+# ---------------------------------------------------------------------------#
+# run the server you want
+# ---------------------------------------------------------------------------#
+time = 5  # 5 seconds delay
+loop = LoopingCall(f=updating_writer, a=(context,))
+loop.start(time, now=False)  # initially delay by time
+StartTcpServer(context, identity=identity, address=("localhost", 5020))