写个modbustcp类

好的，以下是一个使用Python实现Modbus TCP通信的示例类：

import socket

class ModbusTCP:
    def __init__(self, ip_address, port):
        self.ip_address = ip_address
        self.port = port
        self.socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.socket.connect((self.ip_address, self.port))

    def read_coils(self, start_address, quantity):
        # Modbus function code for reading coils is 0x01
        function_code = 0x01
        # Build Modbus request message
        message = bytearray([0x00, 0x01, 0x00, 0x00, 0x00, 0x06, 0x01,
                              (start_address >> 8) & 0xFF, start_address & 0xFF,
                              (quantity >> 8) & 0xFF, quantity & 0xFF])
        # Send Modbus request message and receive response
        response = self._send_message(message, function_code)
        # Extract coil states from response and return as list of booleans
        coil_states = [bool(response[9 + i//8] & (1 << (i % 8))) for i in range(quantity)]
        return coil_states

    def write_coil(self, address, value):
        # Modbus function code for writing a single coil is 0x05
        function_code = 0x05
        # Convert value to 0xFF00 or 0x0000
        value = 0xFF00 if value else 0x0000
        # Build Modbus request message
        message = bytearray([0x00, 0x01, 0x00, 0x00, 0x00, 0x06, 0x05,
                              (address >> 8) & 0xFF, address & 0xFF,
                              (value >> 8) & 0xFF, value & 0xFF])
        # Send Modbus request message and receive response
        self._send_message(message, function_code)

    def _send_message(self, message, function_code):
        # Modbus transaction identifier is just set to 0x00
        transaction_id = 0x00
        # Modbus protocol identifier is 0x0000 for Modbus TCP
        protocol_id = 0x0000
        # Length of message is length of message field plus 6 bytes for header
        length = len(message) + 6
        # Build Modbus TCP header
        header = bytearray([transaction_id >> 8, transaction_id & 0xFF,
                             protocol_id >> 8, protocol_id & 0xFF,
                             length >> 8, length & 0xFF,
                             0x00, 0x00,
                             0x00, 0x00,
                             function_code])
        # Concatenate header and message to form complete Modbus TCP packet
        packet = header + message
        # Send packet to server and receive response
        self.socket.send(packet)
        response = self.socket.recv(1024)
        # Verify Modbus TCP header
        if len(response) < 9:
            raise Exception('Invalid Modbus TCP response')
        response_transaction_id = (response[0] << 8) | response[1]
        response_protocol_id = (response[2] << 8) | response[3]
        response_length = (response[4] << 8) | response[5]
        response_unit_id = response[6]
        response_function_code = response[7]