Modbus TCP

Example

All function codes for Modbus TCP/IP are supported. You can use the client like this:

#!/usr/bin/env python
# scripts/examples/simple_tcp_client.py
import socket

from umodbus import conf
from umodbus.client import tcp

# Enable values to be signed (default is False).
conf.SIGNED_VALUES = True

sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.connect(('localhost', 502))

# Returns a message or Application Data Unit (ADU) specific for doing
# Modbus TCP/IP.
message = tcp.write_multiple_coils(slave_id=1, starting_address=1, values=[1, 0, 1, 1])

# Response depends on Modbus function code. This particular returns the
# amount of coils written, in this case it is.
response = tcp.send_message(message, sock)

sock.close()

API

umodbus.client.tcp.send_message(adu, sock)[source]

Send ADU over socket to to server and return parsed response.

Parameters:
  • adu – Request ADU.
  • sock – Socket instance.
Returns:

Parsed response from server.
umodbus.client.tcp.parse_response_adu(resp_adu, req_adu=None)[source]

Parse response ADU and return response data. Some functions require request ADU to fully understand request ADU.

Parameters:
  • resp_adu – Resonse ADU.
  • req_adu – Request ADU, default None.
Returns:

Response data.
umodbus.client.tcp.read_coils(slave_id, starting_address, quantity)[source]

Return ADU for Modbus function code 01: Read Coils.

Parameters:slave_id – Number of slave.
Returns:Byte array with ADU.
umodbus.client.tcp.read_discrete_inputs(slave_id, starting_address, quantity)[source]

Return ADU for Modbus function code 02: Read Discrete Inputs.

Parameters:slave_id – Number of slave.
Returns:Byte array with ADU.
umodbus.client.tcp.read_holding_registers(slave_id, starting_address, quantity)[source]

Return ADU for Modbus function code 03: Read Holding Registers.

Parameters:slave_id – Number of slave.
Returns:Byte array with ADU.
umodbus.client.tcp.read_input_registers(slave_id, starting_address, quantity)[source]

Return ADU for Modbus function code 04: Read Input Registers.

Parameters:slave_id – Number of slave.
Returns:Byte array with ADU.
umodbus.client.tcp.write_single_coil(slave_id, address, value)[source]

Return ADU for Modbus function code 05: Write Single Coil.

Parameters:slave_id – Number of slave.
Returns:Byte array with ADU.
umodbus.client.tcp.write_single_register(slave_id, address, value)[source]

Return ADU for Modbus function code 06: Write Single Register.

Parameters:slave_id – Number of slave.
Returns:Byte array with ADU.
umodbus.client.tcp.write_multiple_coils(slave_id, starting_address, values)[source]

Return ADU for Modbus function code 15: Write Multiple Coils.

Parameters:slave_id – Number of slave.
Returns:Byte array with ADU.
umodbus.client.tcp.write_multiple_registers(slave_id, starting_address, values)[source]

Return ADU for Modbus function code 16: Write Multiple Registers.

Parameters:slave_id – Number of slave.
Returns:Byte array with ADU.