写一个modbus协议栈代码

Modbus协议栈是一种常用的串行通信协议，常用于工业自动化控制系统中。下面是一个简单的Modbus协议栈代码示例，仅供参考：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdbool.h>

// Modbus函数码
#define READ_COILS              0x01
#define READ_DISCRETE_INPUTS    0x02
#define READ_HOLDING_REGISTERS  0x03
#define READ_INPUT_REGISTERS    0x04
#define WRITE_SINGLE_COIL       0x05
#define WRITE_SINGLE_REGISTER  0x06
#define WRITE_MULTIPLE_COILS    0x0F
#define WRITE_MULTIPLE_REGISTERS 0x10

// Modbus响应帧长度
#define READ_COILS_RESPONSE_LENGTH              5
#define READ_DISCRETE_INPUTS_RESPONSE_LENGTH    5
#define READ_HOLDING_REGISTERS_RESPONSE_LENGTH  5
#define READ_INPUT_REGISTERS_RESPONSE_LENGTH    5
#define WRITE_SINGLE_COIL_RESPONSE_LENGTH       5
#define WRITE_SINGLE_REGISTER_RESPONSE_LENGTH  5
#define WRITE_MULTIPLE_COILS_RESPONSE_LENGTH    5
#define WRITE_MULTIPLE_REGISTERS_RESPONSE_LENGTH 5

// Modbus协议栈结构体
typedef struct {
    int sockfd;         // Socket文件描述符
    char *ip_address;   // 服务器IP地址
    int port;           // 服务器端口号
    bool is_connected;  // 是否连接
    int timeout;        // 超时时间
} modbus_t;

// 连接到Modbus服务器
bool modbus_connect(modbus_t *mb) {
    // TODO: 实现连接逻辑
    return true;
}

// 读取线圈状态
bool modbus_read_coils(modbus_t *mb, int slave_address, int start_address, int quantity, uint8_t *data) {
    // TODO: 实现读取逻辑
    return true;
}

// 读取离散输入状态
bool modbus_read_discrete_inputs(modbus_t *mb, int slave_address, int start_address, int quantity, uint8_t *data) {
    // TODO: 实现读取逻辑
    return true;
}

// 读取保持寄存器
bool modbus_read_holding_registers(modbus_t *mb, int slave_address, int start_address, int quantity, uint16_t *data) {
    // TODO: 实现读取逻辑
    return true;
}

// 读取输入寄存器
bool modbus_read_input_registers(modbus_t *mb, int slave_address, int start_address, int quantity, uint16_t *data) {
    // TODO: 实现读取逻辑
    return true;
}

// 写单个线圈
bool modbus_write_single_coil(modbus_t *mb, int slave_address, int coil_address, bool value) {
    // TODO: 实现写入逻辑
    return true;
}

// 写单个寄存器
bool modbus_write_single_register(modbus_t *mb, int slave_address, int register_address, uint16_t value) {
    // TODO: 实现写入逻辑
    return true;
}

// 写多个线圈
bool modbus_write_multiple_coils(modbus_t *mb, int slave_address, int start_address,