"# \u57fa\u4e8e Modbus \u534f\u8bae\u7684\u670d\u52a1\u5668\u6a21\u62df\u5b9e\u73b0\uff0c\u652f\u6301 TCP\u3001TCP_PI\u548c RTU\u4e09\u79cd\u6a21\u5f0f\n\n> 2024-04-21 | 2024-04-21\n> https:\/\/www.modbus.cn\/en\/27722.html\n\n**Modbus\u7f16\u7a0b\u5f00\u53d1**\n\n---\n\n\u5728\u73b0\u4ee3\u5de5\u4e1a\u81ea\u52a8\u5316\u9886\u57df\uff0cModbus \u534f\u8bae\u4f5c\u4e3a\u4e00\u79cd\u7b80\u5355\u800c\u5e7f\u6cdb\u4f7f\u7528\u7684\u901a\u4fe1\u534f\u8bae\uff0c\u88ab\u5e7f\u6cdb\u5e94\u7528\u4e8e\u5404\u79cd\u8bbe\u5907\u548c\u7cfb\u7edf\u4e4b\u95f4\u7684\u901a\u4fe1\u3002\u672c\u6587\u5c06\u63a2\u8ba8\u5982\u4f55\u4f7f\u7528 Modbus \u534f\u8bae\u6784\u5efa\u4e00\u4e2a\u6a21\u62df\u7684\u670d\u52a1\u5668\uff0c\u8be5\u670d\u52a1\u5668\u80fd\u591f\u5904\u7406\u6765\u81ea\u5ba2\u6237\u7aef\u7684\u5404\u79cd\u8bf7\u6c42\uff0c\u5e76\u5728\u7279\u5b9a\u6761\u4ef6\u4e0b\u6a21\u62df\u5f02\u5e38\u6216\u7279\u6b8a\u884c\u4e3a\uff0c\u4ece\u800c\u4e3a\u5f00\u53d1\u548c\u6d4b\u8bd5\u73af\u5883\u63d0\u4f9b\u4e00\u4e2a\u5b9e\u7528\u7684\u5de5\u5177\u3002\n\n\u5b8c\u6574\u4ee3\u7801\uff08\u4e2d\u6587\u6ce8\u91ca\uff09\uff1a\n\n```\n#include <errno.h>\n#include <modbus.h>\n#include <stdio.h>\n#include <stdlib.h>\n#include <string.h>\n#include <unistd.h>\n\n\/\/ \u4e3a\u4e86\u517c\u5bb9 Windows \u548c Unix \u7cfb\u7edf\u5305\u542b\u4e0d\u540c\u7684\u5934\u6587\u4ef6\n#ifdef _WIN32\n# include <winsock2.h>\n#else\n# include <sys\/socket.h>\n#endif\n\n\/* \u5728 MinGW \u5e73\u53f0\u4e0a\u5b9a\u4e49 MSG_NOSIGNAL *\/\n#ifndef MSG_NOSIGNAL\n# define MSG_NOSIGNAL 0\n#endif\n\n#include \"unit-test.h\"\n\nenum {\n    TCP,\n    TCP_PI,\n    RTU\n};\n\nint main(int argc, char *argv[])\n{\n    int s = -1;  \/\/ socket \u53e5\u67c4\u521d\u59cb\u5316\u4e3a\u65e0\u6548\n    modbus_t *ctx;  \/\/ Modbus \u4e0a\u4e0b\u6587\n    modbus_mapping_t *mb_mapping;  \/\/ Modbus \u6620\u5c04\n    int rc;  \/\/ \u8fd4\u56de\u7801\n    int i;\n    int use_backend;  \/\/ \u4f7f\u7528\u7684\u540e\u7aef\u7c7b\u578b\n    uint8_t *query;  \/\/ \u67e5\u8be2\u7f13\u51b2\u533a\n    int header_length;\n    char *ip_or_device;  \/\/ IP \u6216\u8bbe\u5907\u8def\u5f84\n\n    \/\/ \u547d\u4ee4\u884c\u53c2\u6570\u89e3\u6790\uff0c\u786e\u5b9a\u4f7f\u7528\u7684\u534f\u8bae\u7c7b\u578b\n    if (argc > 1) {\n        if (strcmp(argv[1], \"tcp\") == 0) {\n            use_backend = TCP;\n        } else if (strcmp(argv[1], \"tcppi\") == 0) {\n            use_backend = TCP_PI;\n        } else if (strcmp(argv[1], \"rtu\") == 0) {\n            use_backend = RTU;\n        } else {\n            printf(\"Modbus server for unit testing.\\n\");\n            printf(\"Usage:\\n  %s [tcp|tcppi|rtu] [<ip or device>]\\n\", argv[0]);\n            printf(\"Eg. tcp 127.0.0.1 or rtu \/dev\/ttyUSB0\\n\\n\");\n            return -1;\n        }\n    } else {\n        use_backend = TCP;  \/\/ \u9ed8\u8ba4\u4f7f\u7528 TCP\n    }\n\n    \/\/ \u6839\u636e\u4f7f\u7528\u7684\u534f\u8bae\u7c7b\u578b\uff0c\u8bbe\u7f6e IP \u6216\u8bbe\u5907\u8def\u5f84\n    if (argc > 2) {\n        ip_or_device = argv[2];\n    } else {\n        switch (use_backend) {\n        case TCP:\n            ip_or_device = \"127.0.0.1\";\n            break;\n        case TCP_PI:\n            ip_or_device = \"::1\";\n            break;\n        case RTU:\n            ip_or_device = \"\/dev\/ttyUSB0\";\n            break;\n        default:\n            break;\n        }\n    }\n\n    \/\/ \u521d\u59cb\u5316 Modbus \u4e0a\u4e0b\u6587\n    if (use_backend == TCP) {\n        ctx = modbus_new_tcp(ip_or_device, 1502);\n        query = malloc(MODBUS_TCP_MAX_ADU_LENGTH);\n    } else if (use_backend == TCP_PI) {\n        ctx = modbus_new_tcp_pi(ip_or_device, \"1502\");\n        query = malloc(MODBUS_TCP_MAX_ADU_LENGTH);\n    } else {\n        ctx = modbus_new_rtu(ip_or_device, 115200, 'N', 8, 1);\n        modbus_set_slave(ctx, SERVER_ID);\n        query = malloc(MODBUS_RTU_MAX_ADU_LENGTH);\n    }\n\n    header_length = modbus_get_header_length(ctx);\n\n    modbus_set_debug(ctx, TRUE);  \/\/ \u8bbe\u7f6e\u8c03\u8bd5\u6a21\u5f0f\n\n    \/\/ \u521b\u5efa Modbus \u6620\u5c04\n    mb_mapping = modbus_mapping_new_start_address(\n        UT_BITS_ADDRESS,\n        UT_BITS_NB,\n        UT_INPUT_BITS_ADDRESS,\n        UT_INPUT_BITS_NB,\n        UT_REGISTERS_ADDRESS,\n        UT_REGISTERS_NB_MAX,\n        UT_INPUT_REGISTERS_ADDRESS,\n        UT_INPUT_REGISTERS_NB);\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    \/\/ \u521d\u59cb\u5316\u8f93\u5165\u5bc4\u5b58\u5668\u548c\u7ebf\u5708\u7684\u503c\n    modbus_set_bits_from_bytes(\n        mb_mapping->tab_input_bits, 0, UT_INPUT_BITS_NB, UT_INPUT_BITS_TAB);\n\n    for (i = 0; i < UT_INPUT_REGISTERS_NB; i++) {\n        mb_mapping->tab_input_registers[i] = UT_INPUT_REGISTERS_TAB[i];\n    }\n\n    \/\/ \u76d1\u542c\u8fde\u63a5\u8bf7\u6c42\n    if (use_backend == TCP) {\n        s = modbus_tcp_listen(ctx, 1);\n        modbus_tcp_accept(ctx, &s);\n    } else if (use_backend == TCP_PI) {\n        s = modbus_tcp_pi_listen(ctx, 1);\n        modbus_tcp_pi_accept(ctx, &s);\n    } else {\n        rc = modbus_connect(ctx);\n        if (rc == -1) {\n            fprintf(stderr, \"Unable to connect %s\\n\", modbus_strerror(errno));\n            modbus_free(ctx);\n            return -1;\n        }\n    }\n\n    \/\/ \u670d\u52a1\u5668\u4e3b\u5faa\u73af\uff0c\u5904\u7406\u8bf7\u6c42\n    for (;;) {\n        do {\n            rc = modbus_receive(ctx, query);\n            \/\/ \u8fc7\u6ee4\u7684\u67e5\u8be2\u8fd4\u56de 0\n        } while (rc == 0);\n\n        \/\/ CRC \u9519\u8bef\u7b49\u4e0d\u9700\u8981\u5173\u95ed\u8fde\u63a5\u7684\u9519\u8bef\n        if (rc == -1 && errno != EMBBADCRC) {\n            \/\/ \u9000\u51fa\n            break;\n        }\n\n        \/\/ \u7279\u6b8a\u7684\u670d\u52a1\u5668\u884c\u4e3a\u7528\u4e8e\u6d4b\u8bd5\u5ba2\u6237\u7aef\n        if (query[header_length] == 0x03) {\n            \/\/ \u8bfb\u4fdd\u6301\u5bc4\u5b58\u5668\n            if (MODBUS_GET_INT16_FROM_INT8(query, header_length + 3) ==\n                UT_REGISTERS_NB_SPECIAL) {\n                printf(\"Set an incorrect number of values\\n\");\n                MODBUS_SET_INT16_TO_INT8(\n                    query, header_length + 3, UT_REGISTERS_NB_SPECIAL - 1);\n            } else if (MODBUS_GET_INT16_FROM_INT8(query, header_length + 1) ==\n                       UT_REGISTERS_ADDRESS_SPECIAL) {\n                printf(\"Reply to this special register address by an exception\\n\");\n                modbus_reply_exception(ctx, query, MODBUS_EXCEPTION_SLAVE_OR_SERVER_BUSY);\n                continue;\n            } else if (MODBUS_GET_INT16_FROM_INT8(query, header_length + 1) ==\n                       UT_REGISTERS_ADDRESS_INVALID_TID_OR_SLAVE) {\n                const int RAW_REQ_LENGTH = 5;\n                uint8_t raw_req[] = {(use_backend == RTU) ? INVALID_SERVER_ID : 0xFF,\n                                     0x03,\n                                     0x02,\n                                     0x00,\n                                     0x00};\n\n                printf(\"Reply with an invalid TID or slave\\n\");\n                modbus_send_raw_request(ctx, raw_req, RAW_REQ_LENGTH * sizeof(uint8_t));\n                continue;\n            } else if (MODBUS_GET_INT16_FROM_INT8(query, header_length + 1) ==\n                       UT_REGISTERS_ADDRESS_SLEEP_500_MS) {\n                printf(\"Sleep 0.5 s before replying\\n\");\n                usleep(500000);\n            } else if (MODBUS_GET_INT16_FROM_INT8(query, header_length + 1) ==\n                       UT_REGISTERS_ADDRESS_BYTE_SLEEP_5_MS) {\n                \/\/ \u5bf9 TCP \u6a21\u5f0f\u6d4b\u8bd5\u4f4e\u7ea7\u522b\u64cd\u4f5c\n                uint8_t req[] = \"\\x00\\x1C\\x00\\x00\\x00\\x05\\xFF\\x03\\x02\\x00\\x00\";\n                int req_length = 11;\n                int w_s = modbus_get_socket(ctx);\n                if (w_s == -1) {\n                    fprintf(stderr, \"Unable to get a valid socket in special test\\n\");\n                    continue;\n                }\n\n                \/\/ \u590d\u5236\u4e8b\u52a1ID\n                req[1] = query[1];\n                for (i = 0; i < req_length; i++) {\n                    printf(\"(%.2X)\", req[i]);\n                    usleep(5000);\n                    rc = send(w_s, (const char *) (req + i), 1, MSG_NOSIGNAL);\n                    if (rc == -1) {\n                        break;\n                    }\n                }\n                continue;\n            }\n        }\n\n        \/\/ \u56de\u590d\u5ba2\u6237\u7aef\n        rc = modbus_reply(ctx, query, rc, mb_mapping);\n        if (rc == -1) {\n            break;\n        }\n    }\n\n    printf(\"Quit the loop: %s\\n\", modbus_strerror(errno));\n\n    \/\/ \u6e05\u7406\u8d44\u6e90\n    if (use_backend == TCP) {\n        if (s != -1) {\n            close(s);\n        }\n    }\n    modbus_mapping_free(mb_mapping);\n    free(query);\n    modbus_close(ctx);\n    modbus_free(ctx);\n\n    return 0;\n}\n\n```\n\n### 1. \u7a0b\u5e8f\u6982\u8ff0\n\n\u672c\u7a0b\u5e8f\u662f\u4e00\u4e2a\u57fa\u4e8e Modbus \u534f\u8bae\u7684\u670d\u52a1\u5668\u6a21\u62df\u5b9e\u73b0\uff0c\u652f\u6301 TCP\u3001TCP_PI\uff08TCP Protocol Independent\uff09\u548c RTU\uff08Remote Terminal Unit\uff09\u4e09\u79cd\u6a21\u5f0f\u3002\u8be5\u670d\u52a1\u5668\u901a\u8fc7\u89e3\u6790\u547d\u4ee4\u884c\u53c2\u6570\u6765\u8bbe\u5b9a\u5de5\u4f5c\u6a21\u5f0f\u548c\u901a\u4fe1\u7aef\u53e3\u6216\u8bbe\u5907\u3002\u5176\u4e3b\u8981\u529f\u80fd\u5305\u62ec\u76d1\u542c\u6765\u81ea\u5ba2\u6237\u7aef\u7684\u8bf7\u6c42\u3001\u5904\u7406\u6807\u51c6\u7684\u8bfb\u5199\u5bc4\u5b58\u5668\u64cd\u4f5c\uff0c\u5e76\u5728\u9700\u8981\u65f6\u56de\u5e94\u7279\u5b9a\u7684\u5f02\u5e38\u6216\u8fdb\u884c\u7279\u6b8a\u7684\u64cd\u4f5c\u6a21\u62df\u3002\n\n### 2. \u7a0b\u5e8f\u7ed3\u6784\u548c\u5173\u952e\u5b9e\u73b0\n\n#### 2.1 \u521d\u59cb\u5316\u548c\u914d\u7f6e\n\n\u7a0b\u5e8f\u9996\u5148\u901a\u8fc7\u547d\u4ee4\u884c\u53c2\u6570\u786e\u5b9a\u901a\u4fe1\u6a21\u5f0f\uff08TCP\u3001TCP_PI\u3001RTU\uff09\uff0c\u5e76\u6839\u636e\u9009\u62e9\u7684\u6a21\u5f0f\u521b\u5efa\u76f8\u5e94\u7684 Modbus \u4e0a\u4e0b\u6587\u3002\u6b64\u4e0a\u4e0b\u6587\u7528\u4e8e\u914d\u7f6e\u670d\u52a1\u5668\u7684\u7f51\u7edc\u6216\u4e32\u884c\u901a\u4fe1\u53c2\u6570\uff0c\u4f8b\u5982 IP \u5730\u5740\u548c\u7aef\u53e3\u53f7\u6216\u4e32\u884c\u7aef\u53e3\u914d\u7f6e\u3002\n\n#### 2.2 \u6620\u5c04\u548c\u5185\u5b58\u5206\u914d\n\n\u901a\u8fc7 `modbus_mapping_new_start_address` \u51fd\u6570\uff0c\u7a0b\u5e8f\u4e3a\u4e0d\u540c\u7c7b\u578b\u7684\u5bc4\u5b58\u5668\uff08\u5982\u7ebf\u5708\u3001\u79bb\u6563\u8f93\u5165\u3001\u4fdd\u6301\u5bc4\u5b58\u5668\u548c\u8f93\u5165\u5bc4\u5b58\u5668\uff09\u5206\u914d\u5e76\u521d\u59cb\u5316\u5185\u5b58\u3002\u8fd9\u4e9b\u5bc4\u5b58\u5668\u7684\u503c\u53ef\u4ee5\u901a\u8fc7 Modbus \u547d\u4ee4\u8fdb\u884c\u8bbf\u95ee\u548c\u4fee\u6539\uff0c\u662f\u670d\u52a1\u5668\u4e0e\u5ba2\u6237\u7aef\u4ea4\u4e92\u7684\u6838\u5fc3\u3002\n\n#### 2.3 \u8bf7\u6c42\u5904\u7406\u5faa\u73af\n\n\u670d\u52a1\u5668\u8fd0\u884c\u5728\u4e00\u4e2a\u65e0\u9650\u5faa\u73af\u4e2d\uff0c\u4e0d\u65ad\u5730\u8c03\u7528 `modbus_receive` \u51fd\u6570\u6765\u7b49\u5f85\u548c\u63a5\u6536\u5ba2\u6237\u7aef\u7684\u8bf7\u6c42\u3002\u6536\u5230\u8bf7\u6c42\u540e\uff0c\u670d\u52a1\u5668\u4f1a\u6839\u636e\u8bf7\u6c42\u7684\u529f\u80fd\u7801\u548c\u6570\u636e\u5904\u7406\u8bf7\u6c42\u3002\u5bf9\u4e8e\u6807\u51c6\u7684\u8bfb\u5199\u8bf7\u6c42\uff0c\u670d\u52a1\u5668\u5c06\u4fee\u6539\u6216\u8fd4\u56de\u6620\u5c04\u4e2d\u7684\u5bc4\u5b58\u5668\u503c\u3002\u5bf9\u4e8e\u7279\u6b8a\u7684\u6d4b\u8bd5\u547d\u4ee4\uff0c\u5982\u6545\u610f\u56de\u590d\u9519\u8bef\u7684\u5bc4\u5b58\u5668\u6570\u91cf\u6216\u6a21\u62df\u5ef6\u8fdf\u54cd\u5e94\uff0c\u670d\u52a1\u5668\u5219\u6267\u884c\u76f8\u5e94\u7684\u7279\u6b8a\u884c\u4e3a\u3002\n\n#### 2.4 \u7279\u6b8a\u884c\u4e3a\u6a21\u62df\n\n\u4e3a\u4e86\u589e\u5f3a\u6d4b\u8bd5\u7684\u80fd\u529b\uff0c\u670d\u52a1\u5668\u80fd\u591f\u8bc6\u522b\u7279\u5b9a\u7684\u8bf7\u6c42\uff0c\u5e76\u636e\u6b64\u89e6\u53d1\u9884\u5b9a\u4e49\u7684\u884c\u4e3a\uff0c\u4f8b\u5982\uff1a\n\n- \u56de\u590d\u5f02\u5e38\u4fe1\u606f\uff0c\u6a21\u62df\u8bbe\u5907\u5fd9\u6216\u901a\u4fe1\u9519\u8bef\u3002\n\n- \u5728\u54cd\u5e94\u4e4b\u524d\u6545\u610f\u5ef6\u8fdf\u4e00\u5b9a\u65f6\u95f4\uff0c\u6a21\u62df\u7f51\u7edc\u5ef6\u8fdf\u3002\n\n- \u5bf9\u4e8e\u975e\u6cd5\u7684\u8bf7\u6c42\u5730\u5740\u6216\u6570\u91cf\uff0c\u8fd4\u56de\u9519\u8bef\u4fe1\u606f\u3002\n\n\u8fd9\u4e9b\u529f\u80fd\u4f7f\u5f97\u8be5\u670d\u52a1\u5668\u4e0d\u4ec5\u53ef\u4ee5\u7528\u4f5c\u5e38\u89c4\u7684 Modbus \u670d\u52a1\u5668\uff0c\u8fd8\u53ef\u4ee5\u4f5c\u4e3a\u6d4b\u8bd5\u5ba2\u6237\u7aef\u6216\u5176\u4ed6\u670d\u52a1\u5668\u5b9e\u73b0\u7684\u6709\u529b\u5de5\u5177\u3002\n\n### 3. \u5e94\u7528\u573a\u666f\n\n\u6b64\u6a21\u62df\u670d\u52a1\u5668\u7684\u5e94\u7528\u573a\u666f\u5305\u62ec\u4f46\u4e0d\u9650\u4e8e\uff1a\n\n- **\u5f00\u53d1\u9636\u6bb5**\uff1a\u5f00\u53d1\u4eba\u5458\u53ef\u4ee5\u4f7f\u7528\u6b64\u670d\u52a1\u5668\u6a21\u62df\u5404\u79cd\u8bbe\u5907\uff0c\u9a8c\u8bc1\u548c\u8c03\u8bd5\u5ba2\u6237\u7aef\u5e94\u7528\u3002\n\n- **\u81ea\u52a8\u5316\u6d4b\u8bd5**\uff1a\u6d4b\u8bd5\u4eba\u5458\u53ef\u4ee5\u5229\u7528\u5176\u6a21\u62df\u5f02\u5e38\u7684\u80fd\u529b\uff0c\u589e\u5f3a\u5bf9 Modbus \u5ba2\u6237\u7aef\u8f6f\u4ef6\u7684\u5065\u58ee\u6027\u6d4b\u8bd5\u3002\n\n- **\u6559\u5b66\u548c\u6f14\u793a**\uff1a\u6559\u80b2\u5de5\u4f5c\u8005\u53ef\u4ee5\u7528\u5b83\u6765\u5411\u5b66\u751f\u5c55\u793a Modbus \u534f\u8bae\u7684\u5de5\u4f5c\u539f\u7406\u548c\u8c03\u8bd5\u65b9\u6cd5\u3002\n\n### \u7ed3\u8bed\n\n\u901a\u8fc7\u6784\u5efa\u4e00\u4e2a\u529f\u80fd\u4e30\u5bcc\u7684 Modbus \u6a21\u62df\u670d\u52a1\u5668\uff0c\u5f00\u53d1\u8005\u548c\u6d4b\u8bd5\u8005\u53ef\u4ee5\u5728\u5f00\u53d1\u521d\u671f\u5c31\u53d1\u73b0\u5e76\u89e3\u51b3\u6f5c\u5728\u7684\u95ee\u9898\uff0c\u8fd9\u5bf9\u4e8e\u4fdd\u8bc1\u6700\u7ec8\u4ea7\u54c1\u7684\u8d28\u91cf\u548c\u7a33\u5b9a\u6027\u81f3\u5173\u91cd\u8981\u3002\u6b64\u5916\uff0c\u8fd9\u6837\u7684\u5de5\u5177\u4e5f\u6781\u5927\u5730\u4fc3\u8fdb\u4e86\u5bf9 Modbus \u534f\u8bae\u6df1\u5165\u7406\u89e3\u548c\u5e94\u7528\u7684\u5b66\u4e60\u3002\n\n---\n*modbus.cn*\n"