安装libmodbus

sudo apt install libmodbus-dev 

构建工程目录

mkdir modbus_test cd modbus_test mkdir src touch CMakelists.txt touch src/main.cc 

编写server代码，main.cc

#include  #include  #include  #include  #include  #define SERVER_ID       1       //从端设备地址 #include  using namespace std; int main(int argc, char *argv[]) {     int server_socket = -1;     modbus_t *ctx;     modbus_mapping_t *mb_mapping;     ctx = modbus_new_tcp(NULL,502);     modbus_set_debug(ctx,FALSE);      //modbus_set_slave(ctx,SERVER_ID);      //申请内存区用于存放寄存器数据     mb_mapping = modbus_mapping_new(8,8,10,10);     if(mb_mapping == NULL)     {         fprintf(stderr,"Failed mapping:%s\n",modbus_strerror(errno));         modbus_free(ctx);         return -1;     }      //开始监听端口     server_socket = modbus_tcp_listen(ctx,1);     if(server_socket == -1)     {         fprintf(stderr,"Unable to listen TCP.\n");         modbus_free(ctx);         return -1;     }       // 开始接收数据     modbus_tcp_accept(ctx, &server_socket);      printf("accept\n");     while(1)     {         uint8_t query[MODBUS_TCP_MAX_ADU_LENGTH];         int rc;          rc = modbus_receive(ctx,query); //获取查询报文         if(rc >= 0)         {             for (int i = 0; i < rc; ++i) {                 printf("%02x ", query[i]);             }             printf("\n");              /* rc is the query size */             //mb_mapping->tab_registers[1] = 0x2333;   // 将2333写入地址为1的保持寄存器，可简单理解为发送到客户端             //modbus_reply(ctx,query,rc,mb_mapping); // 回复响应报文             modbus_reply_exception(ctx, query, 1);             //cout<tab_registers[0]<

project(modbus_test)  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -O0 -std=c++17 ${CMAKE_CXX_FLAGS}")   #include_directories(src) aux_source_directory(src SRCS)  add_executable(${PROJECT_NAME} ${SRCS}) target_link_libraries(${PROJECT_NAME} pthread modbus) 

mkdir build cd build cmake .. make sudo ./modbus_test