目录
一、原理及工具
Modbus Slaves软件的使用：传送门
Modbus 协议原理：传送门
Modbus poll 和 Modbus slave调试工具下载：传送门
二、实验流程及相关源码
(1)设置ip和端口号
打开Modbus slave进行相关设置(注意这里IP和端口号可以自己进行相应设置)，具体如下：
(2)设置从站id
初始显示地址(Address)和显示行数(Quantity)及表格行数(Rows)
(3)查看报文
在Display-》Communication中可以看到发送(Tx)和接收(Rx)的报文
(4)源码及测试
Modbus从站读写寄存器相关API函数如下,注意下面的代码只能读正数不能读负数，若想读负数请自行脑补或到文末下载代码：
/* modbus.h
*/
#ifndef MODBUSPP_MODBUS_H
#define MODBUSPP_MODBUS_H
#include <cstring>
#include <stdint.h>
#include <string>
#ifdef ENABLE_MODBUSPP_LOGGING
#include <cstdio>
#define LOG(fmt, ...) printf("[ modbuspp ]" fmt, ##__VA_ARGS__)
#else
#define LOG(...) (void)0
#endif
#ifdef _WIN32
// WINDOWS socket
#define _WINSOCK_DEPRECATED_NO_WARNINGS
#include <winsock2.h>
#pragma comment(lib, "Ws2_32.lib")
using X_SOCKET = SOCKET;
using ssize_t = int;
#define X_ISVALIDSOCKET(s) ((s) != INVALID_SOCKET)
#define X_CLOSE_SOCKET(s) closesocket(s)
#define X_ISCONNECTSUCCEED(s) ((s) != SOCKET_ERROR)
#else
// Berkeley socket
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
using X_SOCKET = int;
#define X_ISVALIDSOCKET(s) ((s) >= 0)
#define X_CLOSE_SOCKET(s) close(s)
#define X_ISCONNECTSUCCEED(s) ((s) >= 0)
#endif
using SOCKADDR = struct sockaddr;
using SOCKADDR_IN = struct sockaddr_in;
#define MAX_MSG_LENGTH 260
///Function Code
#define READ_COILS 0x01
#define READ_INPUT_BITS 0x02
#define READ_REGS 0x03
#define READ_INPUT_REGS 0x04
#define WRITE_COIL 0x05
#define WRITE_REG 0x06
#define WRITE_COILS 0x0F
#define WRITE_REGS 0x10
///Exception Codes
#define EX_ILLEGAL_FUNCTION 0x01 // Function Code not Supported
#define EX_ILLEGAL_ADDRESS 0x02 // Output Address not exists
#define EX_ILLEGAL_VALUE 0x03 // Output Value not in Range
#define EX_SERVER_FAILURE 0x04 // Slave Deive Fails to process request
#define EX_ACKNOWLEDGE 0x05 // Service Need Long Time to Execute
#define EX_SERVER_BUSY 0x06 // Server Was Unable to Accept MB Request PDU
#define EX_NEGATIVE_ACK 0x07
#define EX_MEM_PARITY_PROB 0x08
#define EX_GATEWAY_PROBLEMP 0x0A // Gateway Path not Available
#define EX_GATEWYA_PROBLEMF 0x0B // Target Device Failed to Response
#define EX_BAD_DATA 0XFF // Bad Data lenght or Address
#define BAD_CON -1
/// Modbus Operator Class
/**
* Modbus Operator Class
* Providing networking support and mobus operation support.
*/
class modbus
{
public:
bool err{};
int err_no{};
std::string error_msg;
modbus(std::string host, uint16_t port);
~modbus();
bool modbus_connect();
void modbus_close() const;
void modbus_set_slave_id(int id);
int modbus_read_coils(uint16_t address, uint16_t amount, bool *buffer);
int modbus_read_input_bits(uint16_t address, uint16_t amount, bool *buffer);
int modbus_read_holding_registers(uint16_t address, uint16_t amount, uint16_t *buffer);
int modbus_read_input_registers(uint16_t address, uint16_t amount, uint16_t *buffer);
int modbus_write_coil(uint16_t address, const bool &to_write);
int modbus_write_register(uint16_t address, const uint16_t &value);
int modbus_write_coils(uint16_t address, uint16_t amount, const bool *value);
int modbus_write_registers(uint16_t address, uint16_t amount, const uint16_t *value);
private:
bool _connected{};
uint16_t PORT{};
uint32_t _msg_id{};
int _slaveid{};
std::string HOST;
X_SOCKET _socket{};
SOCKADDR_IN _server{};
#ifdef _WIN32
WSADATA wsadata;
#endif
inline void modbus_build_request(uint8_t *to_send, uint16_t address, int func) const;
int modbus_read(uint16_t address, uint16_t amount, int func);
int modbus_write(uint16_t address, uint16_t amount, int func, const uint16_t *value);
inline ssize_t modbus_send(uint8_t *to_send, size_t length);
inline ssize_t modbus_receive(uint8_t *buffer) const;
void modbuserror_handle(const uint8_t *msg, int func);
inline void set_bad_con();
inline void set_bad_input();
};
/**
* Main Constructor of Modbus Connector Object
* @param host IP Address of Host
* @param port Port for the TCP Connection
* @return A Modbus Connector Object
*/
modbus::modbus(std::string host, uint16_t port = 502)
{
HOST = host;
PORT = port;
_slaveid = 1;
_msg_id = 1;
_connected = false;
err = false;
err_no = 0;
error_msg = "";
}
/**
* Destructor of Modbus Connector Object
*/
modbus::~modbus(void) = default;
/**
* Modbus Slave ID Setter
* @param id ID of the Modbus Server Slave
*/
void modbus::modbus_set_slave_id(int id)
{
_slaveid = id;
}
/**
* Build up a Modbus/TCP Connection
* @return If A Connection Is Successfully Built
*/
bool modbus::modbus_connect()
{
if (HOST.empty() || PORT == 0)
{
LOG("Missing Host and Port");
return false;
}
else
{
LOG("Found Proper Host %s and Port %d", HOST.c_str(), PORT);
}
#ifdef _WIN32
if (WSAStartup(0x0202, &wsadata))
{
return false;
}
#endif
_socket = socket(AF_INET, SOCK_STREAM, 0);
if (!X_ISVALIDSOCKET(_socket))
{
LOG("Error Opening Socket");
#ifdef _WIN32
WSACleanup();
#endif
return false;
}
else
{
LOG("Socket Opened Successfully");
}
#ifdef WIN32
const DWORD timeout = 20;
#else
struct timeval timeout
{
};
timeout.tv_sec = 20; // after 20 seconds connect() will timeout
timeout.tv_usec = 0;
#endif
setsockopt(_socket, SOL_SOCKET, SO_SNDTIMEO, (const char *)&timeout, sizeof(timeout));
setsockopt(_socket, SOL_SOCKET, SO_RCVTIMEO, (const char *)&timeout, sizeof(timeout));
_server.sin_family = AF_INET;
_server.sin_addr.s_addr = inet_addr(HOST.c_str());
_server.sin_port = htons(PORT);
if (!X_ISCONNECTSUCCEED(connect(_socket, (SOCKADDR *)&_server, sizeof(_server))))
{
LOG("Connection Error");
#ifdef _WIN32
WSACleanup();
#endif
return false;
}
LOG("Connected");
_connected = true;
return true;
}
/**
* Close the Modbus/TCP Connection
*/
void modbus::modbus_close() const
{
X_CLOSE_SOCKET(_socket);
#ifdef _WIN32
WSACleanup();
#endif
LOG("Socket Closed");
}
/**
* Modbus Request Builder
* @param to_send Message Buffer to Be Sent
* @param address Reference Address
* @param func Modbus Functional Code
*/
void modbus::modbus_build_request(uint8_t *to_send, uint16_t address, int func) const
{
to_send[0] = (uint8_t)(_msg_id >> 8u);
to_send[1] = (uint8_t)(_msg_id & 0x00FFu);
to_send[2] = 0;
to_send[3] = 0;
to_send[4] = 0;
to_send[6] = (uint8_t)_slaveid;
to_send[7] = (uint8_t)func;
to_send[8] = (uint8_t)(address >> 8u);
to_send[9] = (uint8_t)(address & 0x00FFu);
}
/**
* Write Request Builder and Sender
* @param address Reference Address
* @param amount Amount of data to be Written
* @param func Modbus Functional Code
* @param value Data to Be Written
*/
int modbus::modbus_write(uint16_t address, uint16_t amount, int func, const uint16_t *value)
{
int status = 0;
uint8_t *to_send;
if (func == WRITE_COIL || func == WRITE_REG)
{
to_send = new uint8_t[12];
modbus_build_request(to_send, address, func);
to_send[5] = 6;
to_send[10] = (uint8_t)(value[0] >> 8u);
to_send[11] = (uint8_t)(value[0] & 0x00FFu);
status = modbus_send(to_send, 12);
}
else if (func == WRITE_REGS)
{
to_send = new uint8_t[13 + 2 * amount];
modbus_build_request(to_send, address, func);
to_send[5] = (uint8_t)(7 + 2 * amount);
to_send[10] = (uint8_t)(amount >> 8u);
to_send[11] = (uint8_t)(amount & 0x00FFu);
to_send[12] = (uint8_t)(2 * amount);
for (int i = 0; i < amount; i++)
{
to_send[13 + 2 * i] = (uint8_t)(value[i] >> 8u);
to_send[14 + 2 * i] = (uint8_t)(value[i] & 0x00FFu);
}
status = modbus_send(to_send, 13 + 2 * amount);
}
else if (func == WRITE_COILS)
{
to_send = new uint8_t[14 + (amount - 1) / 8];
modbus_build_request(to_send, address, func);
to_send[5] = (uint8_t)(7 + (amount + 7) / 8);
to_send[10] = (uint8_t)(amount >> 8u);
to_send[11] = (uint8_t)(amount & 0x00FFu);
to_send[12] = (uint8_t)((amount + 7) / 8);
for (int i = 0; i < (amount + 7) / 8; i++)
to_send[13 + i] = 0; // init needed before summing!
for (int i = 0; i < amount; i++)
{
to_send[13 + i / 8] += (uint8_t)(value[i] << (i % 8u));
}
status = modbus_send(to_send, 14 + (amount - 1) / 8);
}
delete[] to_send;
return status;
}
/**
* Read Request Builder and Sender
* @param address Reference Address
* @param amount Amount of Data to Read
* @param func Modbus Functional Code
*/
int modbus::modbus_read(uint16_t address, uint16_t amount, int func)
{
uint8_t to_send[12];
modbus_build_request(to_send, address, func);
to_send[5] = 6;
to_send[10] = (uint8_t)(amount >> 8u);
to_send[11] = (uint8_t)(amount & 0x00FFu);
return modbus_send(to_send, 12);
}
/**
* Read Holding Registers
* MODBUS FUNCTION 0x03
* @param address Reference Address
* @param amount Amount of Registers to Read
* @param buffer Buffer to Store Data Read from Registers
*/
int modbus::modbus_read_holding_registers(uint16_t address, uint16_t amount, uint16_t *buffer)
{
if (_connected)
{
modbus_read(address, amount, READ_REGS);
uint8_t to_rec[MAX_MSG_LENGTH];
ssize_t k = modbus_receive(to_rec);
if (k == -1)
{
set_bad_con();
return BAD_CON;
}
modbuserror_handle(to_rec, READ_REGS);
if (err)
return err_no;
for (auto i = 0; i < amount; i++)
{
buffer[i] = ((uint16_t)to_rec[9u + 2u * i]) << 8u;
buffer[i] += (uint16_t)to_rec[10u + 2u * i];
}
return 0;
}
else
{
set_bad_con();
return BAD_CON;
}
}
/**
* Read Input Registers
* MODBUS FUNCTION 0x04
* @param address Reference Address
* @param amount Amount of Registers to Read
* @param buffer Buffer to Store Data Read from Registers
*/
int modbus::modbus_read_input_registers(uint16_t address, uint16_t amount, uint16_t *buffer)
{
if (_connected)
{
modbus_read(address, amount, READ_INPUT_REGS);
uint8_t to_rec[MAX_MSG_LENGTH];
ssize_t k = modbus_receive(to_rec);
if (k == -1)
{
set_bad_con();
return BAD_CON;
}
modbuserror_handle(to_rec, READ_INPUT_REGS);
if (err)
return err_no;
for (auto i = 0; i < amount; i++)
{
buffer[i] = ((uint16_t)to_rec[9u + 2u * i]) << 8u;
buffer[i] += (uint16_t)to_rec[10u + 2u * i];
}
return 0;
}
else
{
set_bad_con();
return BAD_CON;
}
}
/**
* Read Coils
* MODBUS FUNCTION 0x01
* @param address Reference Address
* @param amount Amount of Coils to Read
* @param buffer Buffer to Store Data Read from Coils
*/
int modbus::modbus_read_coils(uint16_t address, uint16_t amount, bool *buffer)
{
if (_connected)
{
if (amount > 2040)
{
set_bad_input();
return EX_BAD_DATA;
}
modbus_read(address, amount, READ_COILS);
uint8_t to_rec[MAX_MSG_LENGTH];
ssize_t k = modbus_receive(to_rec);
if (k == -1)
{
set_bad_con();
return BAD_CON;
}
modbuserror_handle(to_rec, READ_COILS);
if (err)
return err_no;
for (auto i = 0; i < amount; i++)
{
buffer[i] = (bool)((to_rec[9u + i / 8u] >> (i % 8u)) & 1u);
}
return 0;
}
else
{
set_bad_con();
return BAD_CON;
}
}
/**
* Read Input Bits(Discrete Data)
* MODBUS FUNCITON 0x02
* @param address Reference Address
* @param amount Amount of Bits to Read
* @param buffer Buffer to store Data Read from Input Bits
*/
int modbus::modbus_read_input_bits(uint16_t address, uint16_t amount, bool *buffer)
{
if (_connected)
{
if (amount > 2040)
{
set_bad_input();
return EX_BAD_DATA;
}
modbus_read(address, amount, READ_INPUT_BITS);
uint8_t to_rec[MAX_MSG_LENGTH];
ssize_t k = modbus_receive(to_rec);
if (k == -1)
{
set_bad_con();
return BAD_CON;
}
if (err)
return err_no;
for (auto i = 0; i < amount; i++)
{
buffer[i] = (bool)((to_rec[9u + i / 8u] >> (i % 8u)) & 1u);
}
modbuserror_handle(to_rec, READ_INPUT_BITS);
return 0;
}
else
{
return BAD_CON;
}
}
/**
* Write Single Coils
* MODBUS FUNCTION 0x05
* @param address Reference Address
* @param to_write Value to be Written to Coil
*/
int modbus::modbus_write_coil(uint16_t address, const bool &to_write)
{
if (_connected)
{
int value = to_write * 0xFF00;
modbus_write(address, 1, WRITE_COIL, (uint16_t *)&value);
uint8_t to_rec[MAX_MSG_LENGTH];
ssize_t k = modbus_receive(to_rec);
if (k == -1)
{
set_bad_con();
return BAD_CON;
}
modbuserror_handle(to_rec, WRITE_COIL);
if (err)
return err_no;
return 0;
}
else
{
set_bad_con();
return BAD_CON;
}
}
/**
* Write Single Register
* FUCTION 0x06
* @param address Reference Address
* @param value Value to Be Written to Register
*/
int modbus::modbus_write_register(uint16_t address, const uint16_t &value)
{
if (_connected)
{
modbus_write(address, 1, WRITE_REG, &value);
uint8_t to_rec[MAX_MSG_LENGTH];
ssize_t k = modbus_receive(to_rec);
if (k == -1)
{
set_bad_con();
return BAD_CON;
}
modbuserror_handle(to_rec, WRITE_COIL);
if (err)
return err_no;
return 0;
}
else
{
set_bad_con();
return BAD_CON;
}
}
/**
* Write Multiple Coils
* MODBUS FUNCTION 0x0F
* @param address Reference Address
* @param amount Amount of Coils to Write
* @param value Values to Be Written to Coils
*/
int modbus::modbus_write_coils(uint16_t address, uint16_t amount, const bool *value)
{
if (_connected)
{
uint16_t *temp = new uint16_t[amount];
for (int i = 0; i < amount; i++)
{
temp[i] = (uint16_t)value[i];
}
modbus_write(address, amount, WRITE_COILS, temp);
delete[] temp;
uint8_t to_rec[MAX_MSG_LENGTH];
ssize_t k = modbus_receive(to_rec);
if (k == -1)
{
set_bad_con();
return BAD_CON;
}
modbuserror_handle(to_rec, WRITE_COILS);
if (err)
return err_no;
return 0;
}
else
{
set_bad_con();
return BAD_CON;
}
}
/**
* Write Multiple Registers
* MODBUS FUNCION 0x10
* @param address Reference Address
* @param amount Amount of Value to Write
* @param value Values to Be Written to the Registers
*/
int modbus::modbus_write_registers(uint16_t address, uint16_t amount, const uint16_t *value)
{
if (_connected)
{
modbus_write(address, amount, WRITE_REGS, value);
uint8_t to_rec[MAX_MSG_LENGTH];
ssize_t k = modbus_receive(to_rec);
if (k == -1)
{
set_bad_con();
return BAD_CON;
}
modbuserror_handle(to_rec, WRITE_REGS);
if (err)
return err_no;
return 0;
}
else
{
set_bad_con();
return BAD_CON;
}
}
/**
* Data Sender
* @param to_send Request to Be Sent to Server
* @param length Length of the Request
* @return Size of the request
*/
ssize_t modbus::modbus_send(uint8_t *to_send, size_t length)
{
_msg_id++;
return send(_socket, (const char *)to_send, (size_t)length, 0);
}
/**
* Data Receiver
* @param buffer Buffer to Store the Data Retrieved
* @return Size of Incoming Data
*/
ssize_t modbus::modbus_receive(uint8_t *buffer) const
{
return recv(_socket, (char *)buffer, 1024, 0);
}
void modbus::set_bad_con()
{
err = true;
error_msg = "BAD CONNECTION";
}
void modbus::set_bad_input()
{
err = true;
error_msg = "BAD FUNCTION INPUT";
}
/**
* Error Code Handler
* @param msg Message Received from the Server
* @param func Modbus Functional Code
*/
void modbus::modbuserror_handle(const uint8_t *msg, int func)
{
err = false;
error_msg = "NO ERR";
if (msg[7] == func + 0x80)
{
err = true;
switch (msg[8])
{
case EX_ILLEGAL_FUNCTION:
error_msg = "1 Illegal Function";
break;
case EX_ILLEGAL_ADDRESS:
error_msg = "2 Illegal Address";
break;
case EX_ILLEGAL_VALUE:
error_msg = "3 Illegal Value";
break;
case EX_SERVER_FAILURE:
error_msg = "4 Server Failure";
break;
case EX_ACKNOWLEDGE:
error_msg = "5 Acknowledge";
break;
case EX_SERVER_BUSY:
error_msg = "6 Server Busy";
break;
case EX_NEGATIVE_ACK:
error_msg = "7 Negative Acknowledge";
break;
case EX_MEM_PARITY_PROB:
error_msg = "8 Memory Parity Problem";
break;
case EX_GATEWAY_PROBLEMP:
error_msg = "10 Gateway Path Unavailable";
break;
case EX_GATEWYA_PROBLEMF:
error_msg = "11 Gateway Target Device Failed to Respond";
break;
default:
error_msg = "UNK";
break;
}
}
}
#endif //MODBUSPP_MODBUS_H测试代码如下：
/*test.cpp
*/
#include "modbus.h"
int main(int argc, char **argv)
{
// create a modbus object
modbus mb = modbus("127.0.0.1", 502);
// set slave id
mb.modbus_set_slave_id(1);
// connect with the server
mb.modbus_connect();
// read coil function 0x01
bool read_coil;
mb.modbus_read_coils(0, 1, &read_coil);
// read input bits(discrete input) function 0x02
bool read_bits;
mb.modbus_read_input_bits(0, 1, &read_bits);
// read holding registers function 0x03
uint16_t read_holding_regs[1];
mb.modbus_read_holding_registers(0, 1, read_holding_regs);
// read input registers function 0x04
uint16_t read_input_regs[1];
mb.modbus_read_input_registers(0, 1, read_input_regs);
// write single coil function 0x05
mb.modbus_write_coil(0, true);
// write single reg function 0x06
mb.modbus_write_register(0, 123);
// write multiple coils function 0x0F
bool write_cols[4] = {true, true, true, true};
mb.modbus_write_coils(0, 4, write_cols);
// write multiple regs function 0x10
uint16_t write_regs[4] = {123, 123, 123};
mb.modbus_write_registers(0, 4, write_regs);
// close connection and free the memory
mb.modbus_close();
return 0;
}三、效果
含有负数数据的读写：传送门