Modbus Server and Client

Implementations in Python 3 can be found in server.py and client.py.

Dependencies

numpy

Installation

Using a virtual environment (recommended), install with:

python -m venv venv && source venv/bin/activate
(venv) pip3 install modbus

If you wish to run with the default modbus/tcp port 502/tcp, consider creating and activating the virtualenv using sudo.

Usage Examples

Server

The IANA defined default TCP port for modbus/tcp is 502/tcp. To run on this low-numbered port requires root privileges.

sudo python3 -m modbus.server ...to run server in commandline

For Register Read, the server sends value starting from 1 and incrementing upto 6000. For example, the client wants to read with FuncCode=3, Address=0, and Length=4. Then the server's reply for values will be 1,2,3,4 for the first read and values will increment for every subsequent read.
For Coil Reads, the server sends back values 85,86... for the required length.

Client:

from modbus.client import *
c = client(host='HOSTNAME')     # Change HOSTNAME to Server IP address, defaults to localhost
c.read()                        # To read 10 Input Registers from Address 0
c.read(FC=3, ADR=10, LEN=8)     # To read 8 Holding Registers from Address 10
c.write(11,22,333,4444)         # To write Holding Registers from Address 0
c.write(11,22,333,4444, ADR=10) # To write Holding Registers from Address 10
c.write(11,22, FC=15, ADR=10)   # To write Coils from Address 10
fc()                            # To get the supported Function Codes

Supported Function Codes:

| Code | Description | |----- | ------------------------------ | | 1 | Read Coils or Digital Outputs | | 2 | Read Digital Inputs | | 3 | Read Holding Registers | | 4 | Read Input Registers | | 5 | Write Single Coil | | 6 | Write Single Register | | 15 | Write Coils or Digital Outputs | | 16 | Write Holding Registers |

Modbus

Install / Use

README