#include <modbus.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>

#define MODBUS_PORT 1502
#define MODBUS_ADDRESS 1
#define REGISTER_COUNT 10

int main() {
    modbus_t *ctx;
    modbus_mapping_t *mb_mapping;
    int socket;

    // Create Modbus TCP context
    ctx = modbus_new_tcp("0.0.0.0", MODBUS_PORT);
    if (ctx == NULL) {
        fprintf(stderr, "Unable to allocate libmodbus context\n");
        return -1;
    }

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

    // Initialize registers with sample data
    for (int i = 0; i < REGISTER_COUNT; i++) {
        mb_mapping->tab_registers[i] = i * 10;
    }

    // Listen for incoming connections
    socket = modbus_tcp_listen(ctx, 1);
    if (socket == -1) {
        fprintf(stderr, "Unable to listen for connections: %s\n", modbus_strerror(errno));
        modbus_mapping_free(mb_mapping);
        modbus_free(ctx);
        return -1;
    }

    printf("Modbus server is running on port %d...\n", MODBUS_PORT);

    // Accept and handle connections
    while (1) {
        int client_socket = modbus_tcp_accept(ctx, &socket);
        if (client_socket == -1) {
            fprintf(stderr, "Connection failed: %s\n", modbus_strerror(errno));
            continue;
        }

        while (1) {
            uint8_t query[MODBUS_TCP_MAX_ADU_LENGTH];
            int rc = modbus_receive(ctx, query);
            if (rc > 0) {
                modbus_reply(ctx, query, rc, mb_mapping);
            } else if (rc == -1) {
                break;
            }
        }
        close(client_socket);
    }

    // Cleanup
    close(socket);
    modbus_mapping_free(mb_mapping);
    modbus_free(ctx);
    return 0;
}






#include <modbus.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>

#define MODBUS_SERVER_IP "127.0.0.1"
#define MODBUS_PORT 1502
#define REGISTER_START 0
#define REGISTER_COUNT 10

int main() {
    modbus_t *ctx;
    uint16_t tab_reg[REGISTER_COUNT];

    // Create Modbus TCP context
    ctx = modbus_new_tcp(MODBUS_SERVER_IP, MODBUS_PORT);
    if (ctx == NULL) {
        fprintf(stderr, "Unable to allocate libmodbus context\n");
        return -1;
    }

    // Connect to the Modbus server
    if (modbus_connect(ctx) == -1) {
        fprintf(stderr, "Connection failed: %s\n", modbus_strerror(errno));
        modbus_free(ctx);
        return -1;
    }

    printf("Connected to Modbus server.\n");

    // Read registers
    if (modbus_read_registers(ctx, REGISTER_START, REGISTER_COUNT, tab_reg) == -1) {
        fprintf(stderr, "Failed to read registers: %s\n", modbus_strerror(errno));
        modbus_close(ctx);
        modbus_free(ctx);
        return -1;
    }

    printf("Registers read from server:\n");
    for (int i = 0; i < REGISTER_COUNT; i++) {
        printf("Register %d: %d\n", i, tab_reg[i]);
    }

    // Cleanup
    modbus_close(ctx);
    modbus_free(ctx);
    return 0;
}