libmodbus 庫－Server /Slave仿真程序

　　爲了測試４diac 的modbus 模塊,編寫了一個server 端的仿真程序。將代碼放出了

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <memory.h>
#include <sys/socket.h>
#include "modbus.h"
#include<stdlib.h>
#include <iostream>
/*
compiller command
  clang++  -I /usr/local/include/modbus -L /usr/local/lib -lmodbus  
modbusServerSimulator.cpp -o modbusServerSimulator
*/

using namespace std; 
int main(void)
{    int s = -1;
    int i = 0;
    int rc = 0;
    modbus_t *ctx = NULL;
    modbus_mapping_t *mb_mapping = NULL;
  
     cout<<"modbus Slave"<<endl;
    //打開端口: ip, port
    ctx = modbus_new_tcp("127.0.0.1", 502);
    modbus_set_debug(ctx, TRUE);
       s = modbus_tcp_listen(ctx, 1);
       if (s==-1)
       {
           cout<<"Unable to listen TCP！"<<endl;
       } 
       modbus_tcp_accept(ctx, &s);
    cout<<"connected"<<endl;
    mb_mapping = modbus_mapping_new(MODBUS_MAX_READ_BITS,
                                MODBUS_MAX_WRITE_BITS,
                                MODBUS_MAX_READ_REGISTERS,
                                MODBUS_MAX_WRITE_REGISTERS);
    if (mb_mapping == NULL) {
        fprintf(stderr, "Failed to allocate the mapping: %s\n",
                modbus_strerror(errno));
        modbus_free(ctx);
        return -1;
    }
     //設置從機地址
    modbus_set_slave(ctx, 1);
    uint8_t query[MODBUS_TCP_MAX_ADU_LENGTH];
   //初始化幾個寄存器
   for (int i=0;i<MODBUS_MAX_READ_REGISTERS;i++)
   mb_mapping->tab_input_registers[i] = i;
    while (1)
    {
       rc = modbus_receive(ctx, query);
        if (rc > 0) {          
            modbus_reply(ctx, query, rc, mb_mapping); 
            cout<<"input registers:";
            for (int i=0;i<8;i++) 
           cout<< mb_mapping->tab_registers[i]<<":" ;
           cout<<endl;   
        } else if (rc  == -1) {       
            break;
        } 
    }

    printf("Quit the loop: %s\n", modbus_strerror(errno));
    modbus_mapping_free(mb_mapping);
    if (s != -1) {
        close(s);
    } 
    modbus_close(ctx);
    modbus_free(ctx);
}

說明

modbus　的相關數據都是放在　mb_mapping 中的。他是一個結構類型，在modbus.h　中定義

typedef struct _modbus_mapping_t {
    int nb_bits;
    int start_bits;
    int nb_input_bits;
    int start_input_bits;
    int nb_input_registers;
    int start_input_registers;
    int nb_registers;
    int start_registers;
    uint8_t *tab_bits;
    uint8_t *tab_input_bits;
    uint16_t *tab_input_registers;
    uint16_t *tab_registers;
} modbus_mapping_t;

應用軟件從這個結構中讀取數據。