"# \u7528C\u8bed\u8a00\u521b\u5efa\u652f\u6301\u591a\u79cd\u6a21\u5f0f\u7684Modbus\u670d\u52a1\u5668\n\n> 2024-04-21 | 2024-04-21\n> https:\/\/www.modbus.cn\/en\/27709.html\n\n**Modbus\u7f16\u7a0b\u5f00\u53d1**\n\n---\n\n\u5728\u5de5\u4e1a\u81ea\u52a8\u5316\u9886\u57df\uff0cModbus \u534f\u8bae\u5e7f\u6cdb\u7528\u4e8e\u8bbe\u5907\u95f4\u7684\u901a\u4fe1\u3002\u672c\u6587\u5c06\u63a2\u8ba8\u5982\u4f55\u4f7f\u7528 C \u8bed\u8a00\u548c libmodbus \u5e93\u6765\u5b9e\u73b0\u4e00\u4e2a\u652f\u6301 TCP \u548c RTU \u4e24\u79cd\u6a21\u5f0f\u7684 Modbus \u670d\u52a1\u5668\u3002\u8fd9\u79cd\u670d\u52a1\u5668\u80fd\u591f\u5904\u7406\u6765\u81ea\u5ba2\u6237\u7aef\u7684\u6570\u636e\u8bf7\u6c42\uff0c\u5e76\u6839\u636e\u8fd9\u4e9b\u8bf7\u6c42\u8fd4\u56de\u76f8\u5e94\u7684\u6570\u636e\u3002\n\n#### Modbus \u534f\u8bae\u7b80\u4ecb\n\nModbus \u662f\u4e00\u4e2a\u5e94\u7528\u5c42\u534f\u8bae\uff0c\u7531 Modicon \u516c\u53f8\uff08\u73b0\u4e3a\u65bd\u8010\u5fb7\u7535\u6c14\u7684\u4e00\u90e8\u5206\uff09\u5728 1979 \u5e74\u4e3a\u4f7f\u7528\u7f16\u7a0b\u903b\u8f91\u63a7\u5236\u5668\uff08PLC\uff09\u8fdb\u884c\u901a\u4fe1\u800c\u5f00\u53d1\u3002\u5b83\u5df2\u6210\u4e3a\u5de5\u4e1a\u9886\u57df\u5185\u4e00\u4e2a\u4e8b\u5b9e\u4e0a\u7684\u6807\u51c6\uff0c\u5e76\u4e14\u5e7f\u6cdb\u7528\u4e8e\u591a\u79cd\u901a\u4fe1\u8bbe\u5907\u4e4b\u95f4\u7684\u4ea4\u4e92\u3002Modbus \u534f\u8bae\u652f\u6301\u591a\u79cd\u901a\u4fe1\u7c7b\u578b\uff0c\u672c\u4f8b\u4e2d\u5c06\u6db5\u76d6 TCP \u548c RTU \u4e24\u79cd\u3002\n\n\u5b8c\u6574\u4ee3\u7801\uff1a\n\n```\n\/\/ \u7248\u6743\u58f0\u660e\u548c\u8bb8\u53ef\u4fe1\u606f\n#include <stdio.h>\n#ifndef _MSC_VER\n#include <unistd.h>  \/\/ UNIX\u6807\u51c6\u51fd\u6570\u5b9a\u4e49\u5e93\n#endif\n#include <errno.h>   \/\/ \u9519\u8bef\u7801\u5b9a\u4e49\n#include <stdlib.h>  \/\/ \u6807\u51c6\u5e93\u5b9a\u4e49\n#include <string.h>  \/\/ \u5b57\u7b26\u4e32\u5904\u7406\u51fd\u6570\n\n#include <modbus.h>  \/\/ \u5f15\u5165modbus\u5e93\n\n#if defined(_WIN32)\n#define close closesocket  \/\/ \u5728Windows\u4e0a\uff0c\u4f7f\u7528closesocket\u51fd\u6570\u4ee3\u66ffclose\n#endif\n\nenum {\n    TCP,\n    RTU\n};\n\nint main(int argc, char *argv[])\n{\n    int s = -1;  \/\/ socket\u63cf\u8ff0\u7b26\u521d\u59cb\u5316\u4e3a-1\n    modbus_t *ctx = NULL;  \/\/ modbus\u4e0a\u4e0b\u6587\u521d\u59cb\u5316\u4e3aNULL\n    modbus_mapping_t *mb_mapping = NULL;  \/\/ modbus\u6620\u5c04\u521d\u59cb\u5316\u4e3aNULL\n    int rc;  \/\/ \u7528\u4e8e\u63a5\u6536\u51fd\u6570\u8fd4\u56de\u503c\n    int use_backend;  \/\/ \u7528\u4e8e\u9009\u62e9\u540e\u7aef\u7c7b\u578b\uff08TCP\u6216RTU\uff09\n\n    \/\/ \u89e3\u6790\u547d\u4ee4\u884c\u53c2\u6570\u4ee5\u786e\u5b9a\u4f7f\u7528TCP\u8fd8\u662fRTU\n    if (argc > 1) {\n        if (strcmp(argv[1], \"tcp\") == 0) {\n            use_backend = TCP;\n        } else if (strcmp(argv[1], \"rtu\") == 0) {\n            use_backend = RTU;\n        } else {\n            printf(\"Usage:\\n  %s [tcp|rtu] - Modbus client to measure data bandwidth\\n\\n\",\n                   argv[0]);\n            exit(1);\n        }\n    } else {\n        \/\/ \u9ed8\u8ba4\u4f7f\u7528TCP\n        use_backend = TCP;\n    }\n\n    \/\/ \u6839\u636e\u6240\u9009\u7684\u540e\u7aef\u521d\u59cb\u5316modbus\u4e0a\u4e0b\u6587\n    if (use_backend == TCP) {\n        ctx = modbus_new_tcp(\"127.0.0.1\", 1502);  \/\/ \u521b\u5efaTCP\u8fde\u63a5\n        s = modbus_tcp_listen(ctx, 1);  \/\/ \u76d1\u542cTCP\u7aef\u53e3\n        modbus_tcp_accept(ctx, &s);  \/\/ \u63a5\u53d7TCP\u8fde\u63a5\n\n    } else {\n        ctx = modbus_new_rtu(\"\/dev\/ttyUSB0\", 115200, 'N', 8, 1);  \/\/ \u521b\u5efaRTU\u8fde\u63a5\n        modbus_set_slave(ctx, 1);  \/\/ \u8bbe\u7f6e\u4ece\u8bbe\u5907\u5730\u5740\n        modbus_connect(ctx);  \/\/ \u8fde\u63a5\u5230\u4ece\u8bbe\u5907\n    }\n\n    \/\/ \u521b\u5efamodbus\u6620\u5c04\n    mb_mapping =\n        modbus_mapping_new(MODBUS_MAX_READ_BITS, 0, MODBUS_MAX_READ_REGISTERS, 0);\n    if (mb_mapping == NULL) {\n        fprintf(stderr, \"Failed to allocate the mapping: %s\\n\", modbus_strerror(errno));\n        modbus_free(ctx);\n        return -1;\n    }\n\n    \/\/ \u4e3b\u5faa\u73af\uff0c\u5904\u7406\u8bf7\u6c42\n    for (;;) {\n        uint8_t query[MODBUS_TCP_MAX_ADU_LENGTH];\n\n        rc = modbus_receive(ctx, query);  \/\/ \u63a5\u6536\u8bf7\u6c42\n        if (rc > 0) {\n            modbus_reply(ctx, query, rc, mb_mapping);  \/\/ \u53d1\u9001\u54cd\u5e94\n        } else if (rc == -1) {\n            \/\/ \u5ba2\u6237\u7aef\u5173\u95ed\u8fde\u63a5\u6216\u53d1\u751f\u9519\u8bef\n            break;\n        }\n    }\n\n    printf(\"Quit the loop: %s\\n\", modbus_strerror(errno));\n\n    \/\/ \u6e05\u7406\u8d44\u6e90\n    modbus_mapping_free(mb_mapping);\n    if (s != -1) {\n        close(s);\n    }\n    \/\/ \u5bf9\u4e8eRTU\u6a21\u5f0f\uff0c\u9700\u8981\u5173\u95ed\u8fde\u63a5\uff0cTCP\u6a21\u5f0f\u4e2d\u5df2\u7531TCP\u5173\u95ed\u5904\u7406\n    modbus_close(ctx);\n    modbus_free(ctx);\n\n    return 0;\n}\n\n```\n\n#### \u73af\u5883\u914d\u7f6e\n\n\u9996\u5148\uff0c\u9700\u8981\u5728\u7cfb\u7edf\u4e2d\u5b89\u88c5 libmodbus \u5e93\uff0c\u5b83\u662f\u4e00\u4e2a\u5f00\u6e90\u7684 C \u8bed\u8a00\u5e93\uff0c\u7528\u4e8e\u5b9e\u73b0 Modbus \u534f\u8bae\u3002\u8fd9\u4e2a\u5e93\u652f\u6301\u591a\u79cd\u64cd\u4f5c\u7cfb\u7edf\u548c\u786c\u4ef6\u5e73\u53f0\u3002\n\n#### \u670d\u52a1\u5668\u7684\u57fa\u672c\u8bbe\u7f6e\n\n\u670d\u52a1\u5668\u7a0b\u5e8f\u5f00\u59cb\u65f6\u9996\u5148\u4f1a\u89e3\u6790\u547d\u4ee4\u884c\u53c2\u6570\u6765\u786e\u5b9a\u662f\u4f7f\u7528 TCP \u8fd8\u662f RTU \u6a21\u5f0f\u3002\u57fa\u4e8e\u6240\u9009\u6a21\u5f0f\uff0c\u7a0b\u5e8f\u5c06\u521d\u59cb\u5316\u4e00\u4e2a\u5bf9\u5e94\u7684 Modbus \u4e0a\u4e0b\u6587\uff08`modbus_t`\uff09\u3002\u4f8b\u5982\uff0c\u5bf9\u4e8e TCP \u6a21\u5f0f\uff0c\u670d\u52a1\u5668\u4f1a\u76d1\u542c\u7279\u5b9a\u7684 IP \u5730\u5740\u548c\u7aef\u53e3\uff1b\u5bf9\u4e8e RTU \u6a21\u5f0f\uff0c\u670d\u52a1\u5668\u5219\u4f1a\u8bbe\u7f6e\u4e32\u884c\u901a\u4fe1\u7684\u53c2\u6570\uff0c\u5982\u6ce2\u7279\u7387\u548c\u5947\u5076\u6821\u9a8c\u7b49\u3002\n\n#### \u6570\u636e\u6620\u5c04\u548c\u76d1\u542c\n\n\u65e0\u8bba\u54ea\u79cd\u6a21\u5f0f\uff0c\u670d\u52a1\u5668\u90fd\u4f1a\u521b\u5efa\u4e00\u4e2a `modbus_mapping_t` \u7ed3\u6784\uff0c\u8fd9\u4e2a\u7ed3\u6784\u7528\u4e8e\u5b58\u50a8\u548c\u7ba1\u7406\u4ece\u8bbe\u5907\u5730\u5740\u7a7a\u95f4\u7684\u6570\u636e\uff0c\u5305\u62ec\u8f93\u5165\u4f4d\u3001\u4fdd\u6301\u5bc4\u5b58\u5668\u7b49\u3002\u63a5\u7740\uff0c\u670d\u52a1\u5668\u8fdb\u5165\u4e3b\u5faa\u73af\uff0c\u7b49\u5f85\u5e76\u5904\u7406\u6765\u81ea\u5ba2\u6237\u7aef\u7684\u8bf7\u6c42\u3002\u5bf9\u4e8e TCP \u8fde\u63a5\uff0c\u670d\u52a1\u5668\u4f1a\u8c03\u7528 `modbus_tcp_accept` \u6765\u63a5\u53d7\u65b0\u7684\u5ba2\u6237\u7aef\u8fde\u63a5\u3002\n\n#### \u8bf7\u6c42\u5904\u7406\n\n\u5f53\u670d\u52a1\u5668\u63a5\u6536\u5230\u4e00\u4e2a\u8bf7\u6c42\u65f6\uff0c\u5b83\u4f1a\u4f7f\u7528 `modbus_receive` \u51fd\u6570\u8bfb\u53d6\u8bf7\u6c42\u6570\u636e\uff0c\u5e76\u6839\u636e\u8bf7\u6c42\u7684\u7c7b\u578b\uff08\u5982\u8bfb\u53d6\u5bc4\u5b58\u5668\u6216\u5199\u5165\u5bc4\u5b58\u5668\uff09\u4f7f\u7528 `modbus_reply` \u51fd\u6570\u53d1\u9001\u54cd\u5e94\u3002\u8fd9\u4e2a\u8fc7\u7a0b\u6d89\u53ca\u5230\u5bf9 `mb_mapping` \u6570\u636e\u7ed3\u6784\u7684\u67e5\u8be2\u548c\u4fee\u6539\u3002\n\n#### \u5f02\u5e38\u5904\u7406\u548c\u8d44\u6e90\u7ba1\u7406\n\n\u5728\u6574\u4e2a\u901a\u4fe1\u8fc7\u7a0b\u4e2d\uff0c\u670d\u52a1\u5668\u9700\u8981\u59a5\u5584\u5904\u7406\u53ef\u80fd\u53d1\u751f\u7684\u5404\u79cd\u9519\u8bef\u60c5\u51b5\uff0c\u5982\u8fde\u63a5\u9519\u8bef\u3001\u6570\u636e\u4f20\u8f93\u9519\u8bef\u7b49\u3002\u6b64\u5916\uff0c\u8fd8\u9700\u8981\u5728\u7a0b\u5e8f\u9000\u51fa\u524d\u91ca\u653e\u6240\u6709\u5df2\u5206\u914d\u7684\u8d44\u6e90\uff0c\u5305\u62ec Modbus \u4e0a\u4e0b\u6587\u548c\u6570\u636e\u6620\u5c04\u7ed3\u6784\u3002\n\n#### \u7ed3\u675f\u8bed\n\n\u901a\u8fc7 libmodbus \u5e93\uff0c\u6211\u4eec\u53ef\u4ee5\u76f8\u5bf9\u7b80\u5355\u5730\u5b9e\u73b0\u4e00\u4e2a\u529f\u80fd\u9f50\u5168\u7684 Modbus \u670d\u52a1\u5668\u3002\u8fd9\u4e0d\u4ec5\u6709\u52a9\u4e8e\u7406\u89e3 Modbus \u534f\u8bae\u7684\u5de5\u4f5c\u539f\u7406\uff0c\u8fd8\u80fd\u591f\u63d0\u4f9b\u4e00\u4e2a\u5f3a\u5927\u7684\u5de5\u5177\uff0c\u7528\u4e8e\u5728\u5b9e\u9645\u7684\u5de5\u4e1a\u5e94\u7528\u4e2d\u8fdb\u884c\u8bbe\u5907\u901a\u4fe1\u548c\u6570\u636e\u7ba1\u7406\u3002\u8fd9\u79cd\u57fa\u4e8e\u6807\u51c6\u7684\u5b9e\u73b0\u65b9\u5f0f\u786e\u4fdd\u4e86\u826f\u597d\u7684\u517c\u5bb9\u6027\u548c\u53ef\u9760\u6027\uff0c\u662f\u8fde\u63a5\u73b0\u4ee3\u5de5\u4e1a\u8bbe\u5907\u7684\u7406\u60f3\u9009\u62e9\u3002\n\n---\n*modbus.cn*\n"