client_sync.py

#!/usr/bin/env python3
"""Pymodbus Synchronous Client Example.

An example of a single threaded synchronous client.

usage::

    client_sync.py [-h] [-c {tcp,udp,serial,tls}]
                    [-f {ascii,rtu,socket,tls}]
                    [-l {critical,error,warning,info,debug}] [-p PORT]
                    [--baudrate BAUDRATE] [--host HOST]

    -h, --help
        show this help message and exit
    -c, --comm {tcp,udp,serial,tls}
        set communication, default is tcp
    -f, --framer {ascii,rtu,socket,tls}
        set framer, default depends on --comm
    -l, --log {critical,error,warning,info,debug}
        set log level, default is info
    -p, --port PORT
        set port
    --baudrate BAUDRATE
        set serial device baud rate
    --host HOST
        set host, default is 127.0.0.1

The corresponding server must be started before e.g. as:

    python3 server_sync.py

"""
import logging
import sys


try:
    import helper
except ImportError:
    print("*** ERROR --> THIS EXAMPLE needs the example directory, please see \n\
          https://pymodbus.readthedocs.io/en/latest/source/examples.html\n\
          for more information.")
    sys.exit(-1)

import pymodbus.client as modbusClient
from pymodbus import ModbusException


_logger = logging.getLogger(__file__)
_logger.setLevel("DEBUG")


def setup_sync_client(description=None, cmdline=None):
    """Run client setup."""
    args = helper.get_commandline(
        server=False,
        description=description,
        cmdline=cmdline,
    )
    _logger.info("### Create client object")
    client = None
    if args.comm == "tcp":
        client = modbusClient.ModbusTcpClient(
            args.host,
            port=args.port,
            # Common optional parameters:
            framer=args.framer,
            timeout=args.timeout,
            #    retries=3,
            # TCP setup parameters
            #    source_address=("localhost", 0),
        )
    elif args.comm == "udp":
        client = modbusClient.ModbusUdpClient(
            args.host,
            port=args.port,
            # Common optional parameters:
            framer=args.framer,
            timeout=args.timeout,
            #    retries=3,
            # UDP setup parameters
            #    source_address=None,
        )
    elif args.comm == "serial":
        client = modbusClient.ModbusSerialClient(
            port=args.port,  # serial port
            # Common optional parameters:
            #    framer=ModbusRtuFramer,
            timeout=args.timeout,
            #    retries=3,
            # Serial setup parameters
            baudrate=args.baudrate,
            #    bytesize=8,
            #    parity="N",
            #    stopbits=1,
            #    handle_local_echo=False,
        )
    elif args.comm == "tls":
        client = modbusClient.ModbusTlsClient(
            args.host,
            port=args.port,
            # Common optional parameters:
            framer=args.framer,
            timeout=args.timeout,
            #    retries=3,
            # TLS setup parameters
            sslctx=modbusClient.ModbusTlsClient.generate_ssl(
                certfile=helper.get_certificate("crt"),
                keyfile=helper.get_certificate("key"),
            #    password=None,
            ),
        )
    return client


def run_sync_client(client, modbus_calls=None):
    """Run sync client."""
    _logger.info("### Client starting")
    client.connect()
    if modbus_calls:
        modbus_calls(client)
    client.close()
    _logger.info("### End of Program")


def run_a_few_calls(client):
    """Test connection works."""
    try:
        rr = client.read_coils(32, 1, slave=1)
        assert len(rr.bits) == 8
        rr = client.read_holding_registers(4, 2, slave=1)
        assert rr.registers[0] == 17
        assert rr.registers[1] == 17
    except ModbusException as exc:
        raise exc

def main(cmdline=None):
    """Combine setup and run."""
    testclient = setup_sync_client(
        description="Run synchronous client.", cmdline=cmdline
    )
    run_sync_client(testclient, modbus_calls=run_a_few_calls)


if __name__ == "__main__":
    main()