linux下TCP与RTU数据转发程序

linux下TCP与RTU数据转发程序

#include 
#include 
#include 
#include 
#include 

#include "modbus.h"

enum {
    TCP,
    RTU
};

int main(int argc, char *argv[])
{
    int socket;
    modbus_t *ctx;
    modbus_mapping_t *mb_mapping;
    int rc;
    int use_backend;

     /* TCP */
    if (argc > 1) {
        if (strcmp(argv[1], "tcp") == 0) {
            use_backend = TCP;
        } else if (strcmp(argv[1], "rtu") == 0) {
            use_backend = RTU;
        } else {
            printf("Usage:\n  %s [tcp|rtu] - Modbus client to measure data bandwith\n\n", argv[0]);
            exit(1);
        }
    } else {
        /* By default */
        use_backend = TCP;
    }

    if (use_backend == TCP) {
        ctx = modbus_new_tcp("127.0.0.1", 1502);
        socket = modbus_tcp_listen(ctx, 1);
        modbus_tcp_accept(ctx, &socket);

    } else {
        ctx = modbus_new_rtu("/dev/ttySAC3", 19200, 'N', 8, 1);
        modbus_set_slave(ctx, 1);
        modbus_connect(ctx);
    }

    mb_mapping = modbus_mapping_new(MODBUS_MAX_READ_BITS, 0,
                                    MODBUS_MAX_READ_REGISTERS, 0);
    if (mb_mapping == NULL) {
        fprintf(stderr, "Failed to allocate the mapping: %s\n",
                modbus_strerror(errno));
        modbus_free(ctx);
        return -1;
    }

    for(;;) {
        uint8_t query[MODBUS_TCP_MAX_ADU_LENGTH];

        rc = modbus_receive(ctx, query);
        if (rc >= 0) {
            modbus_reply(ctx, query, rc, mb_mapping);
        } else {
            /* Connection closed by the client or server */
            break;
        }
    }

    printf("Quit the loop: %s\n", modbus_strerror(errno));

    modbus_mapping_free(mb_mapping);
    close(socket);
    modbus_free(ctx);

    return 0;
}

交叉编译命令：arm-linux-gcc -o test test.c -L. lmodbus,主机测试使用modbus poll，经串口线连接；先启动服务端程序 ./test rtu或./test tcp,再打开modbus poll。
测试结果：
000059-Rx:01 03 28 00 0C 00 00 00 00 00 00 00 00 00 00 00 0C 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0C 16

000072-Tx:01 03 00 00 00 14 45 C5
000073-Rx:01 03 28 00 0C 00 00 00 00 00 00 00 00 00 00 00 0C 00 00 00 00 00 0D 00 00 00 00 00 0D 00 00 00 00 00 00 00 00 00 00 00 00 00 00 1D 0E