以下是一个使用BlueZ开源库实现一个Gatt Server的样例工程，支持蓝牙5.0和可读写的Characteristics：

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <bluetooth/bluetooth.h>
#include <bluetooth/gatt.h>

#define ATT_CID          4

struct bt_att *att;
struct bt_gatt_manager *gatt_manager;
int characteristic_handle;

static void on_write_cb(struct bt_conn *conn, uint8_t err,
                        struct bt_gatt_write_params *params)
{
    if (err) {
        printf("Failed to write data (err %d)\n", err);
        return;
    }

    printf("Data written successfully\n");
}

static ssize_t read_value_cb(struct bt_conn *conn, const struct bt_gatt_attr *attr,
                             void *buf, uint16_t len, uint16_t offset)
{
    static const char value[] = "Hello GATT Client!";
    size_t value_len = sizeof(value);

    return bt_gatt_attr_read(conn, attr, buf, len, offset, value, value_len);
}

static ssize_t write_value_cb(struct bt_conn *conn, const struct bt_gatt_attr *attr,
                              const void *buf, uint16_t len, uint16_t offset,
                              uint8_t flags)
{
    // Handle the incoming data here
    printf("Received data: %.*s\n", len, buf);

    return len;
}

static struct bt_gatt_attr attrs[] = {
    BT_GATT_PRIMARY_SERVICE(BT_UUID_DECLARE_128(BT_UUID_HEART_RATE)),

    BT_GATT_CHARACTERISTIC(BT_UUID_DECLARE_128(BT_UUID_HEART_RATE_MEASUREMENT),
                           BT_GATT_CHRC_READ | BT_GATT_CHRC_NOTIFY),

        BT_GATT_DESCRIPTOR(BT_UUID_DECLARE_128(BT_UUID_CHAR_DESCRIPTION),
                           BT_GATT_PERM_READ, read_value_cb, NULL, NULL),

        BT_GATT_DESCRIPTOR(BT_UUID_DECLARE_128(BT_UUID_CLIENT_CHAR_CONFIG),
                           BT_GATT_PERM_READ | BT_GATT_PERM_WRITE,
                           bt_gatt_attr_read_ccc_cfg, bt_gatt_attr_write_ccc_cfg,
                           (void *)BT_GATT_CCC_NOTIFY),

    BT_GATT_CHARACTERISTIC(BT_UUID_DECLARE_128(BT_UUID_TEMPERATURE_MEASUREMENT),
                           BT_GATT_CHRC_READ | BT_GATT_CHRC_WRITE),

        BT_GATT_DESCRIPTOR(BT_UUID_DECLARE_128(BT_UUID_CHAR_DESCRIPTION),
                           BT_GATT_PERM_READ, read_value_cb, NULL, NULL),

        BT_GATT_DESCRIPTOR(BT_UUID_DECLARE_128(BT_UUID_VALID_RANGE),
                           BT_GATT_PERM_READ,
                           bt_gatt_attr_read_valid_range16, NULL, NULL),

        BT_GATT_DESCRIPTOR(BT_UUID_DECLARE_128(0x2902),
                           0x02 /* FIXME: not always notify */,
                           read_value_cb, write_value_cb, NULL),

    /* Battery Service Declaration */
    BT_GATT_CHARACTERISTIC(BT_UUID_DECLARE_16(0x2a19),
                          (BT_ATT_PERM_READ | 0), // battery level
                          ((BT_ATT_NO_TIMEOUT) << 12)),
};

static void gatt_manager_connected(struct bt_conn *conn)
{
    printf("GATT client connected\n");

    // Enable notifications on the first characteristic
    uint16_t value = BT_GATT_CCC_NOTIFY;
    struct bt_gatt_write_params write_params;

    write_params.data = &value;
    write_params.length = sizeof(value);
    write_params.handle = characteristic_handle + 2; // CCCD handle
    write_params.offset = 0;
    write_params.func = on_write_cb;

    bt_gatt_write(conn, &write_params);
}

static void gatt_manager_disconnected(struct bt_conn *conn)
{
    printf("GATT client disconnected\n");
}

static struct bt_gatt_manager_cb gatt_manager_callbacks = {
    .connected = gatt_manager_connected,
    .disconnected = gatt_manager_disconnected,
};

int main(int argc, char *argv[])
{
    // Initialize Bluetooth
    if (bt_init() < 0) {
        fprintf(stderr, "Failed to initialize Bluetooth\n");
        return -1;
    }

    // Register GATT attributes
    if (bt_gatt_register(attrs, ARRAY_SIZE(attrs)) < 0) {
        fprintf(stderr, "Failed to register GATT attributes\n");
        return -1;
    }

    // Start GATT manager
    gatt_manager = bt_gatt_manager_new();
    
     if (!gatt_manager) {
        fprintf(stderr, "Failed to create GATT manager\n");
        return -1;
     }
    
     bt_gatt_manager_set_coding_format(gatt_manager, BT_GATT_CODING_FORMAT_16);

     // Create ATT layer
     att = bt_att_new(ATT_CID);
     
     if (!att) {
         fprintf(stderr, "Failed to create ATT layer\n");
         return -1;
     }

     // Attach ATT layer with GATT manager
     bt_att_attach(att, g_io_channel_unix_get_fd(bt_g_io_channel_get_io_channel(g_io_channel_default())));

     // Set up callbacks for GATT manager events
     bt_gio_set_watch(GIOChannelEventFlag_Readable | GIOChannelEventFlag_Hup | GIOChannelEventFlag_Error,
                      g_io_channel_unix_get_fd(bt_g_io_channel_get_io_channel(g_io_channel_default())));

      bt_gio_set_callbacks(g_io_channel_unix_get_fd(bt_g_io_channel_get_io_channel(g_io_channel_default())),
                           &gatt_manager_callbacks);

      // Run the main loop
      while (1) {
          g_main_context_iteration(NULL, TRUE);
      }

      // Clean up resources
      bt_att_unref(att);
      bt_gatt_manager_unref(gatt_manager);

      return 0;
}

请注意，此示例代码仅供参考，并可能需要根据具体的需求和硬件配置进行适当的修改。同时，确保你已经正确安装了BlueZ开源库并设置好相关依赖。

希望这可以帮助你开始使用BlueZ开发一个支持蓝牙5.0和可读写Characteristics的Gatt Server。


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