Modbus TCP Server on RaspberryPi

[esch...@gmail.com]

Hello,

i tried some simple examples for both Modbus TCP client and server on my RaspberryPi with arch-linux.

The client function works quite well but the server does not work.

I used following code (from the source -> examples folder -> tcpslave_example.py):

#!/usr/bin/env python
# -*- coding: utf_8 -*-
"""
 Modbus TestKit: Implementation of Modbus protocol in python

 (C)2009 - Luc Jean - luc....@gmail.com
 (C)2009 - Apidev - http://www.apidev.fr

 This is distributed under GNU LGPL license, see license.txt
"""

import sys

#add logging capability
import logging
import threading

import modbus_tk
import modbus_tk.defines as cst
import modbus_tk.modbus as modbus
import modbus_tk.modbus_tcp as modbus_tcp

logger = modbus_tk.utils.create_logger(name="console", record_format="%(message)s")
   
if __name__ == "__main__":
       
    try:
        #Create the server
        server = modbus_tcp.TcpServer()
        logger.info("running...")
        logger.info("enter 'quit' for closing the server")

        server.start()
       
        slave_1 = server.add_slave(1)
        slave_1.add_block('0', cst.HOLDING_REGISTERS, 100, 100)
        while True:
            cmd = sys.stdin.readline()
            args = cmd.split(' ')
            if cmd.find('quit')==0:
                sys.stdout.write('bye-bye\r\n')
                break
            elif args[0]=='add_slave':
                slave_id = int(args[1])
                server.add_slave(slave_id)
                sys.stdout.write('done: slave %d added\r\n' % (slave_id))
            elif args[0]=='add_block':
                slave_id = int(args[1])
                name = args[2]
                block_type = int(args[3])
                starting_address = int(args[4])
                length = int(args[5])
                slave = server.get_slave(slave_id)
                slave.add_block(name, block_type, starting_address, length)
                sys.stdout.write('done: block %s added\r\n' % (name))
            elif args[0]=='set_values':
                slave_id = int(args[1])
                name = args[2]
                address = int(args[3])
                values = []
                for v in args[4:]:
                    values.append(int(v))
                slave = server.get_slave(slave_id)
                slave.set_values(name, address, values)
                values = slave.get_values(name, address, len(values))
                sys.stdout.write('done: values written: %s\r\n' % (str(values)))
            elif args[0]=='get_values':
                slave_id = int(args[1])
                name = args[2]
                address = int(args[3])
                length = int(args[4])
                slave = server.get_slave(slave_id)
                values = slave.get_values(name, address, length)
                sys.stdout.write('done: values read: %s\r\n' % (str(values)))
            else:
                sys.stdout.write("unknown command %s\r\n" % (args[0]))
    finally:
        server.stop()

I start the server with the command "python2 tcpslave_example.py" and then i try to connect with the Modbus testtool "Ananas" but it says "Connection creation failed".

I have also tried connecting to a PLC with Modbus TCP server functionality and it works, but it does not work on the RaspberryPi.

Any suggestions? Thanks in advance!!!

[Luc JEAN]

Hello,

You may have to bind the IP address when creating the server

modbus_tcp.TcpServer(address="10.0.0.15")

I hope it helps

Best

luc

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[esch...@gmail.com]

Thanks, great hint!

BR