void set_attribute(char *svc_uuid, char *chr_uuid, char *desc_uuid) 
{ 
    bt_gatt_h svc, chr, desc = NULL; 
    int ret; ret = bt_gatt_client_get_service(client, svc_uuid, &svc);
    ret = bt_gatt_service_get_characteristic(svc, chr_uuid, &chr); 
    ret = bt_gatt_client_read_value(chr, __bt_gatt_client_read_complete_cb, NULL); 
    
    // If setter or getter are added here, probably they will return NULL 
    // because reading value which is returned by __bt_gatt_client_read_complete_cb must be not completed 
    // at the moment. 
    // Not sure how long it takes to complete read value, hence characteristic handle 'chr' used in this function 
    //  won't be updated with read value. 
    // so simply setter or getter should be defined in __bt_gatt_client_read_complete_cb to ensure reding for the 
    // characteristic is completed. 
    
} 

void __bt_gatt_client_read_complete_cb(int result, bt_gatt_h gatt_handle, void *data) 
{ 
    char *uuid = NULL; bt_gatt_get_uuid(gatt_handle, uuid); 
    g_free(uuid); 
    
    // define setter or getter here using 'gatt_handle'. 
    bt_gatt_get_value(gatt_handle,...); 
    bt_gatt_set_value(gatt_handle,...);

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