写一个软件通讯，modbus tcp协议

下面是一个使用Python编写的Modbus TCP通讯软件示例：

import socket

# Modbus TCP帧结构
class ModbusTCPFrame:
    def __init__(self, unit_id, function_code, data):
        self.transaction_id = 0x0000
        self.protocol_id = 0x0000
        self.length = len(data) + 1
        self.unit_id = unit_id
        self.function_code = function_code
        self.data = data
    
    # 将Modbus TCP帧转换为字节流
    def to_bytes(self):
        return self.transaction_id.to_bytes(2, byteorder='big') + \
               self.protocol_id.to_bytes(2, byteorder='big') + \
               self.length.to_bytes(2, byteorder='big') + \
               self.unit_id.to_bytes(1, byteorder='big') + \
               self.function_code.to_bytes(1, byteorder='big') + \
               self.data

    # 从字节流解析Modbus TCP帧
    @staticmethod
    def from_bytes(data):
        transaction_id = int.from_bytes(data[0:2], byteorder='big')
        protocol_id = int.from_bytes(data[2:4], byteorder='big')
        length = int.from_bytes(data[4:6], byteorder='big')
        unit_id = int.from_bytes(data[6:7], byteorder='big')
        function_code = int.from_bytes(data[7:8], byteorder='big')
        frame_data = data[8:]
        return ModbusTCPFrame(unit_id, function_code, frame_data)

# Modbus TCP客户端
class ModbusTCPClient:
    def __init__(self, host, port, unit_id):
        self.host = host
        self.port = port
        self.unit_id = unit_id
        self.socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.socket.connect((host, port))

    # 发送Modbus TCP请求并接收响应
    def send_request(self, function_code, data):
        frame = ModbusTCPFrame(self.unit_id, function_code, data)
        self.socket.send(frame.to_bytes())
        response = self.socket.recv(1024)
        frame = ModbusTCPFrame.from_bytes(response)
        return frame.data

    # 读取线圈状态
    def read_coils(self, address, count):
        data = address.to_bytes(2, byteorder='big') + \
               count.to_bytes(2, byteorder='big')
        response_data = self.send_request(0x01, data)
        return response_data

    # 写入单个线圈状态
    def write_coil(self, address, value):
        data = address.to_bytes(2, byteorder='big') + \
               (0xFF00 if value else 0x0000).to_bytes(2, byteorder='big')
        response_data = self.send_request(0x05, data)
        return response_data

    # 读取保持寄存器
    def read_holding_registers(self, address, count):
        data = address.to_bytes(2, byteorder='big') + \
               count.to_bytes(2, byteorder='big')
        response_data = self.send_request(0x03, data)
        return response_data

    # 写入单个保持寄存器
    def write_holding_register(self, address, value):
        data = address.to_bytes(2, byteorder='big') + \
               value.to_bytes(2, byteorder='big')
        response_data = self.send_request(0x06, data)
        return response_data

    # 关闭连接
    def close(self):
        self.socket.close()

使用该Modbus TCP客户端可以进行读写线圈状态和保持寄存器的操作。例如，读取线圈状态可以使用以下代码：

client = ModbusTCPClient('192.168.1.10', 502, 1)
coils = client.read_coils(0x0000, 8)
client.close()
print(coils)

其中，`192.168.1.10`是Modbus TCP从设备的IP地址，`502`是Modbus TCP从设备的端口号，`1`是Modbus TCP从设备的设备地址，`0x0000`是线圈地址，`8`是读取的线圈数量。