: 'http://www.modbusdriver.com/modpoll.html:

Usage: modpoll [options] serialport|host
    Arguments:
    serialport    Serial port when using Modbus ASCII or Modbus RTU protocol
                  COM1, COM2 ...                on Windows
                  /dev/ttyS0, /dev/ttyS1 ...    on Linux
                  /dev/ser1, /dev/ser2 ...      on QNX
    host          Host name or dotted ip address when using MODBUS/TCP protocol
    General options:
    -m ascii      Modbus ASCII protocol
    -m rtu        Modbus RTU protocol (default)
    -m tcp        MODBUS/TCP protocol
    -m enc        Encapsulated Modbus RTU over TCP
    -a #          Slave address (1-255, 1 is default)
    -r #          Start reference (1-65536, 100 is default)
    -c #          Number of values to poll (1-100, 1 is default)
    -t 0          Discrete output (coil) data type
    -t 1          Discrete input data type
    -t 3          16-bit input register data type
    -t 3:hex      16-bit input register data type with hex display
    -t 3:int      32-bit integer data type in input register table
    -t 3:mod      32-bit module 10000 data type in input register table
    -t 3:float    32-bit float data type in input register table
    -t 4          16-bit output (holding) register data type (default)
    -t 4:hex      16-bit output (holding) register data type with hex display
    -t 4:int      32-bit integer data type in output (holding) register table
    -t 4:mod      32-bit module 10000 type in output (holding) register table
    -t 4:float    32-bit float data type in output (holding) register table
    -i            Slave operates on big-endian 32-bit integers
    -f            Slave operates on big-endian 32-bit floats
    -1            Poll only once, otherwise poll every second
    -e            Use Daniel/Enron single register 32-bit mode
    -0            First reference is 0 (PDU addressing) instead 1
    Options for MODBUS/TCP:
    -p #          TCP port number (502 is default)
    Options for Modbus ASCII and Modbus RTU:
    -b #          Baudrate (e.g. 9600, 19200, ...) (9600 is default)
    -d #          Databits (7 or 8 for ASCII protocol, 8 for RTU)
    -s #          Stopbits (1 or 2, 1 is default)
    -p none       No parity
    -p even       Even parity (default)
    -p odd        Odd parity
    -4 #          RS-485 mode, RTS on while transmitting and another # ms after
    -o #          Time-out in seconds (0.01 - 10.0, 1.0 s is default)
'

# Lectura de Holding Registers
# addess = 4001 (-a 1) count = 10 (-c = 10) port = 5502 (-p 5502)

    modpoll -m tcp -a 1 -c 10 -p 5502 192.168.56.1

# Escritura de Holding Registers
# addess = 4001 (-a 1) count = 3 (-c = 10) port = 5502 (-p 5502) ... value1 value2 value3

    modpoll -m tcp -a 1 -c 3 -p 5502 192.168.56.1 11 32 56

# To retrieve once 5 floating point values starting from reference 100 with Modbus/TCP from slave device with IP 10.0.0.100:
    
    modpoll -m tcp -t4:float -r 100 -c 5 -1 10.0.0.100