BlueZ D-Bus C , 应用 BLE

Posted 2023-04-14

【中文标题】BlueZ D-Bus C , 应用 BLE

【英文标题】：BlueZ D-Bus C , application BLE

【发布时间】：2018-11-13 12:09:33

【问题描述】：

我正在尝试编写一个搜索附近的蓝牙设备并与它们通信的应用程序。我的应用程序将用 C 语言编写，并打算在 Linux 下运行。

是否有任何教程或示例通过 C 中的 D-Bus 使用 BlueZ？ 此应用程序的目的是从 BLE 中的文件发送数据。

你能帮帮我吗？

【问题讨论】：

这很可能是一个风滚草，因为一开始就缺乏数据和努力，或者更有可能因为“太宽泛”而被关闭。请阅读How to create a Minimal, Complete, and Verifiable example 并访问Help Center 以了解如何提出可回答的问题。祝你好运！

你可以在这里查看：github.com/S3ler/SimpleBluetoothLowEnergySocket

我目前正在为蓝牙经典开发一些示例，您可以在这里找到源代码：gist.github.com/parthitce 和信息最少的博客linumiz.com/category/blog

【参考方案1】：

您可以使用 DBUS 的“StartDiscovery”适配器 API 找到附近的设备。使用下面的示例代码，您应该能够扫描附近的设备（BLE 和 Calssic）。但如果您只想扫描附近的 BLE 设备，您可以使用“SetDiscoveryFilter”API 将传输设置为“le”并开始扫描 BLE 设备（请查看下面的第二个示例）。

/*
 * bluez_adapter_scan.c - Scan for bluetooth devices
 *  - This example scans for new devices after powering the adapter, if any devices
 *    appeared in /org/hciX/dev_XX_YY_ZZ_AA_BB_CC, it is monitered using "InterfaceAdded"
 *    signal and all the properties of the device is printed
 *  - Scanning continues to run until any device is disappered, this happens after 180 seconds
 *    automatically if the device is not used.
 * gcc `pkg-config --cflags glib-2.0 gio-2.0` -Wall -Wextra -o ./bin/bluez_adapter_scan ./bluez_adapter_scan.c `pkg-config --libs glib-2.0 gio-2.0`
 */
#include <glib.h>
#include <gio/gio.h>

GDBusConnection *con;
static void bluez_property_value(const gchar *key, GVariant *value)

    const gchar *type = g_variant_get_type_string(value);

    g_print("\t%s : ", key);
    switch(*type) 
        case 'o':
        case 's':
            g_print("%s\n", g_variant_get_string(value, NULL));
            break;
        case 'b':
            g_print("%d\n", g_variant_get_boolean(value));
            break;
        case 'u':
            g_print("%d\n", g_variant_get_uint32(value));
            break;
        case 'a':
        /* TODO Handling only 'as', but not array of dicts */
            if(g_strcmp0(type, "as"))
                break;
            g_print("\n");
            const gchar *uuid;
            GVariantIter i;
            g_variant_iter_init(&i, value);
            while(g_variant_iter_next(&i, "s", &uuid))
                g_print("\t\t%s\n", uuid);
            break;
        default:
            g_print("Other\n");
            break;
    


static void bluez_device_appeared(GDBusConnection *sig,
                const gchar *sender_name,
                const gchar *object_path,
                const gchar *interface,
                const gchar *signal_name,
                GVariant *parameters,
                gpointer user_data)

    (void)sig;
    (void)sender_name;
    (void)object_path;
    (void)interface;
    (void)signal_name;
    (void)user_data;

    GVariantIter *interfaces;
    const char *object;
    const gchar *interface_name;
    GVariant *properties;

    g_variant_get(parameters, "(&oasasv)", &object, &interfaces);
    while(g_variant_iter_next(interfaces, "&s@asv", &interface_name, &properties)) 
        if(g_strstr_len(g_ascii_strdown(interface_name, -1), -1, "device")) 
            g_print("[ %s ]\n", object);
            const gchar *property_name;
            GVariantIter i;
            GVariant *prop_val;
            g_variant_iter_init(&i, properties);
            while(g_variant_iter_next(&i, "&sv", &property_name, &prop_val))
                bluez_property_value(property_name, prop_val);
            g_variant_unref(prop_val);
        
        g_variant_unref(properties);
    
    return;


#define BT_ADDRESS_STRING_SIZE 18
static void bluez_device_disappeared(GDBusConnection *sig,
                const gchar *sender_name,
                const gchar *object_path,
                const gchar *interface,
                const gchar *signal_name,
                GVariant *parameters,
                gpointer user_data)

    (void)sig;
    (void)sender_name;
    (void)object_path;
    (void)interface;
    (void)signal_name;

    GVariantIter *interfaces;
    const char *object;
    const gchar *interface_name;
    char address[BT_ADDRESS_STRING_SIZE] = '\0';

    g_variant_get(parameters, "(&oas)", &object, &interfaces);
    while(g_variant_iter_next(interfaces, "s", &interface_name)) 
        if(g_strstr_len(g_ascii_strdown(interface_name, -1), -1, "device")) 
            int i;
            char *tmp = g_strstr_len(object, -1, "dev_") + 4;

            for(i = 0; *tmp != '\0'; i++, tmp++) 
                if(*tmp == '_') 
                    address[i] = ':';
                    continue;
                
                address[i] = *tmp;
            
            g_print("\nDevice %s removed\n", address);
            g_main_loop_quit((GMainLoop *)user_data);
        
    
    return;


static void bluez_signal_adapter_changed(GDBusConnection *conn,
                    const gchar *sender,
                    const gchar *path,
                    const gchar *interface,
                    const gchar *signal,
                    GVariant *params,
                    void *userdata)

    (void)conn;
    (void)sender;
    (void)path;
    (void)interface;
    (void)userdata;

    GVariantIter *properties = NULL;
    GVariantIter *unknown = NULL;
    const char *iface;
    const char *key;
    GVariant *value = NULL;
    const gchar *signature = g_variant_get_type_string(params);

    if(g_strcmp0(signature, "(sasvas)") != 0) 
        g_print("Invalid signature for %s: %s != %s", signal, signature, "(sasvas)");
        goto done;
    

    g_variant_get(params, "(&sasvas)", &iface, &properties, &unknown);
    while(g_variant_iter_next(properties, "&sv", &key, &value)) 
        if(!g_strcmp0(key, "Powered")) 
            if(!g_variant_is_of_type(value, G_VARIANT_TYPE_BOOLEAN)) 
                g_print("Invalid argument type for %s: %s != %s", key,
                        g_variant_get_type_string(value), "b");
                goto done;
            
            g_print("Adapter is Powered \"%s\"\n", g_variant_get_boolean(value) ? "on" : "off");
        
        if(!g_strcmp0(key, "Discovering")) 
            if(!g_variant_is_of_type(value, G_VARIANT_TYPE_BOOLEAN)) 
                g_print("Invalid argument type for %s: %s != %s", key,
                        g_variant_get_type_string(value), "b");
                goto done;
            
            g_print("Adapter scan \"%s\"\n", g_variant_get_boolean(value) ? "on" : "off");
        
    
done:
    if(properties != NULL)
        g_variant_iter_free(properties);
    if(value != NULL)
        g_variant_unref(value);


static int bluez_adapter_call_method(const char *method)

    GVariant *result;
    GError *error = NULL;

    result = g_dbus_connection_call_sync(con,
                         "org.bluez",
                    /* TODO Find the adapter path runtime */
                         "/org/bluez/hci0",
                         "org.bluez.Adapter1",
                         method,
                         NULL,
                         NULL,
                         G_DBUS_CALL_FLAGS_NONE,
                         -1,
                         NULL,
                         &error);
    if(error != NULL)
        return 1;

    g_variant_unref(result);
    return 0;


static int bluez_adapter_set_property(const char *prop, GVariant *value)

    GVariant *result;
    GError *error = NULL;

    result = g_dbus_connection_call_sync(con,
                         "org.bluez",
                         "/org/bluez/hci0",
                         "org.freedesktop.DBus.Properties",
                         "Set",
                         g_variant_new("(ssv)", "org.bluez.Adapter1", prop, value),
                         NULL,
                         G_DBUS_CALL_FLAGS_NONE,
                         -1,
                         NULL,
                         &error);
    if(error != NULL)
        return 1;

    g_variant_unref(result);
    return 0;


int main(void)

    GMainLoop *loop;
    int rc;
    guint prop_changed;
    guint iface_added;
    guint iface_removed;

    con = g_bus_get_sync(G_BUS_TYPE_SYSTEM, NULL, NULL);
    if(con == NULL) 
        g_print("Not able to get connection to system bus\n");
        return 1;
    

    loop = g_main_loop_new(NULL, FALSE);

    prop_changed = g_dbus_connection_signal_subscribe(con,
                        "org.bluez",
                        "org.freedesktop.DBus.Properties",
                        "PropertiesChanged",
                        NULL,
                        "org.bluez.Adapter1",
                        G_DBUS_SIGNAL_FLAGS_NONE,
                        bluez_signal_adapter_changed,
                        NULL,
                        NULL);

    iface_added = g_dbus_connection_signal_subscribe(con,
                            "org.bluez",
                            "org.freedesktop.DBus.ObjectManager",
                            "InterfacesAdded",
                            NULL,
                            NULL,
                            G_DBUS_SIGNAL_FLAGS_NONE,
                            bluez_device_appeared,
                            loop,
                            NULL);

    iface_removed = g_dbus_connection_signal_subscribe(con,
                            "org.bluez",
                            "org.freedesktop.DBus.ObjectManager",
                            "InterfacesRemoved",
                            NULL,
                            NULL,
                            G_DBUS_SIGNAL_FLAGS_NONE,
                            bluez_device_disappeared,
                            loop,
                            NULL);

    rc = bluez_adapter_set_property("Powered", g_variant_new("b", TRUE));
    if(rc) 
        g_print("Not able to enable the adapter\n");
        goto fail;
    

    rc = bluez_adapter_call_method("StartDiscovery");
    if(rc) 
        g_print("Not able to scan for new devices\n");
        goto fail;
    

    g_main_loop_run(loop);
    rc = bluez_adapter_call_method("StopDiscovery");
    if(rc)
        g_print("Not able to stop scanning\n");
    g_usleep(100);

    rc = bluez_adapter_set_property("Powered", g_variant_new("b", FALSE));
    if(rc)
        g_print("Not able to disable the adapter\n");
fail:
    g_dbus_connection_signal_unsubscribe(con, prop_changed);
    g_dbus_connection_signal_unsubscribe(con, iface_added);
    g_dbus_connection_signal_unsubscribe(con, iface_removed);
    g_object_unref(con);
    return 0;

使用 SetDiscoveryFilter 仅扫描 BLE 设备的示例。

/*
 * bluez_adapter_filter.c - Set discovery filter, Scan for bluetooth devices
 *  - Control three discovery filter parameter from command line,
 *      - auto/bredr/le
 *      - RSSI (0:very close range to -100:far away)
 *      - UUID (only one as of now)
 *  Example run: ./bin/bluez_adapter_filter bredr 100 00001105-0000-1000-8000-00805f9b34fb
 *  - This example scans for new devices after powering the adapter, if any devices
 *    appeared in /org/hciX/dev_XX_YY_ZZ_AA_BB_CC, it is monitered using "InterfaceAdded"
 *    signal and all the properties of the device is printed
 *  - Device will be removed immediately after it appears in InterfacesAdded signal, so
 *    InterfacesRemoved will be called which quits the main loop
 * gcc `pkg-config --cflags glib-2.0 gio-2.0` -Wall -Wextra -o ./bin/bluez_adapter_filter ./bluez_adapter_filter.c `pkg-config --libs glib-2.0 gio-2.0`
 */
#include <glib.h>
#include <gio/gio.h>

GDBusConnection *con;
static void bluez_property_value(const gchar *key, GVariant *value)

    const gchar *type = g_variant_get_type_string(value);

    g_print("\t%s : ", key);
    switch(*type) 
        case 'o':
        case 's':
            g_print("%s\n", g_variant_get_string(value, NULL));
            break;
        case 'b':
            g_print("%d\n", g_variant_get_boolean(value));
            break;
        case 'u':
            g_print("%d\n", g_variant_get_uint32(value));
            break;
        case 'a':
        /* TODO Handling only 'as', but not array of dicts */
            if(g_strcmp0(type, "as"))
                break;
            g_print("\n");
            const gchar *uuid;
            GVariantIter i;
            g_variant_iter_init(&i, value);
            while(g_variant_iter_next(&i, "s", &uuid))
                g_print("\t\t%s\n", uuid);
            break;
        default:
            g_print("Other\n");
            break;
    


typedef void (*method_cb_t)(GObject *, GAsyncResult *, gpointer);
static int bluez_adapter_call_method(const char *method, GVariant *param, method_cb_t method_cb)

    GError *error = NULL;

    g_dbus_connection_call(con,
                 "org.bluez",
            /* TODO Find the adapter path runtime */
                 "/org/bluez/hci0",
                 "org.bluez.Adapter1",
                 method,
                 param,
                 NULL,
                 G_DBUS_CALL_FLAGS_NONE,
                 -1,
                 NULL,
                 method_cb,
                 &error);
    if(error != NULL)
        return 1;
    return 0;


static void bluez_get_discovery_filter_cb(GObject *con,
                      GAsyncResult *res,
                      gpointer data)

    (void)data;
    GVariant *result = NULL;
    result = g_dbus_connection_call_finish((GDBusConnection *)con, res, NULL);
    if(result == NULL)
        g_print("Unable to get result for GetDiscoveryFilter\n");

    if(result) 
        result = g_variant_get_child_value(result, 0);
        bluez_property_value("GetDiscoveryFilter", result);
    
    g_variant_unref(result);


static void bluez_device_appeared(GDBusConnection *sig,
                const gchar *sender_name,
                const gchar *object_path,
                const gchar *interface,
                const gchar *signal_name,
                GVariant *parameters,
                gpointer user_data)

    (void)sig;
    (void)sender_name;
    (void)object_path;
    (void)interface;
    (void)signal_name;
    (void)user_data;

    GVariantIter *interfaces;
    const char *object;
    const gchar *interface_name;
    GVariant *properties;
    //int rc;

    g_variant_get(parameters, "(&oasasv)", &object, &interfaces);
    while(g_variant_iter_next(interfaces, "&s@asv", &interface_name, &properties)) 
        if(g_strstr_len(g_ascii_strdown(interface_name, -1), -1, "device")) 
            g_print("[ %s ]\n", object);
            const gchar *property_name;
            GVariantIter i;
            GVariant *prop_val;
            g_variant_iter_init(&i, properties);
            while(g_variant_iter_next(&i, "&sv", &property_name, &prop_val))
                bluez_property_value(property_name, prop_val);
            g_variant_unref(prop_val);
        
        g_variant_unref(properties);
    
/*
    rc = bluez_adapter_call_method("RemoveDevice", g_variant_new("(o)", object));
    if(rc)
        g_print("Not able to remove %s\n", object);
*/
    return;


#define BT_ADDRESS_STRING_SIZE 18
static void bluez_device_disappeared(GDBusConnection *sig,
                const gchar *sender_name,
                const gchar *object_path,
                const gchar *interface,
                const gchar *signal_name,
                GVariant *parameters,
                gpointer user_data)

    (void)sig;
    (void)sender_name;
    (void)object_path;
    (void)interface;
    (void)signal_name;

    GVariantIter *interfaces;
    const char *object;
    const gchar *interface_name;
    char address[BT_ADDRESS_STRING_SIZE] = '\0';

    g_variant_get(parameters, "(&oas)", &object, &interfaces);
    while(g_variant_iter_next(interfaces, "s", &interface_name)) 
        if(g_strstr_len(g_ascii_strdown(interface_name, -1), -1, "device")) 
            int i;
            char *tmp = g_strstr_len(object, -1, "dev_") + 4;

            for(i = 0; *tmp != '\0'; i++, tmp++) 
                if(*tmp == '_') 
                    address[i] = ':';
                    continue;
                
                address[i] = *tmp;
            
            g_print("\nDevice %s removed\n", address);
            g_main_loop_quit((GMainLoop *)user_data);
        
    
    return;


static void bluez_signal_adapter_changed(GDBusConnection *conn,
                    const gchar *sender,
                    const gchar *path,
                    const gchar *interface,
                    const gchar *signal,
                    GVariant *params,
                    void *userdata)

    (void)conn;
    (void)sender;
    (void)path;
    (void)interface;
    (void)userdata;

    GVariantIter *properties = NULL;
    GVariantIter *unknown = NULL;
    const char *iface;
    const char *key;
    GVariant *value = NULL;
    const gchar *signature = g_variant_get_type_string(params);

    if(strcmp(signature, "(sasvas)") != 0) 
        g_print("Invalid signature for %s: %s != %s", signal, signature, "(sasvas)");
        goto done;
    

    g_variant_get(params, "(&sasvas)", &iface, &properties, &unknown);
    while(g_variant_iter_next(properties, "&sv", &key, &value)) 
        if(!g_strcmp0(key, "Powered")) 
            if(!g_variant_is_of_type(value, G_VARIANT_TYPE_BOOLEAN)) 
                g_print("Invalid argument type for %s: %s != %s", key,
                        g_variant_get_type_string(value), "b");
                goto done;
            
            g_print("Adapter is Powered \"%s\"\n", g_variant_get_boolean(value) ? "on" : "off");
        
        if(!g_strcmp0(key, "Discovering")) 
            if(!g_variant_is_of_type(value, G_VARIANT_TYPE_BOOLEAN)) 
                g_print("Invalid argument type for %s: %s != %s", key,
                        g_variant_get_type_string(value), "b");
                goto done;
            
            g_print("Adapter scan \"%s\"\n", g_variant_get_boolean(value) ? "on" : "off");
        
    
done:
    if(properties != NULL)
        g_variant_iter_free(properties);
    if(value != NULL)
        g_variant_unref(value);


static int bluez_adapter_set_property(const char *prop, GVariant *value)

    GVariant *result;
    GError *error = NULL;

    result = g_dbus_connection_call_sync(con,
                         "org.bluez",
                         "/org/bluez/hci0",
                         "org.freedesktop.DBus.Properties",
                         "Set",
                         g_variant_new("(ssv)", "org.bluez.Adapter1", prop, value),
                         NULL,
                         G_DBUS_CALL_FLAGS_NONE,
                         -1,
                         NULL,
                         &error);
    if(error != NULL)
        return 1;

    g_variant_unref(result);
    return 0;


static int bluez_set_discovery_filter(char **argv)

    int rc;
    GVariantBuilder *b = g_variant_builder_new(G_VARIANT_TYPE_VARDICT);
    g_variant_builder_add(b, "sv", "Transport", g_variant_new_string(argv[1]));
    g_variant_builder_add(b, "sv", "RSSI", g_variant_new_int16(-g_ascii_strtod(argv[2], NULL)));
    g_variant_builder_add(b, "sv", "DuplicateData", g_variant_new_boolean(FALSE));

    GVariantBuilder *u = g_variant_builder_new(G_VARIANT_TYPE_STRING_ARRAY);
    g_variant_builder_add(u, "s", argv[3]);
    g_variant_builder_add(b, "sv", "UUIDs", g_variant_builder_end(u));

    GVariant *device_dict = g_variant_builder_end(b);
    g_variant_builder_unref(u);
    g_variant_builder_unref(b);
    rc = bluez_adapter_call_method("SetDiscoveryFilter", g_variant_new_tuple(&device_dict, 1), NULL);
    if(rc) 
        g_print("Not able to set discovery filter\n");
        return 1;
    

    rc = bluez_adapter_call_method("GetDiscoveryFilters",
            NULL,
            bluez_get_discovery_filter_cb);
    if(rc) 
        g_print("Not able to get discovery filter\n");
        return 1;
    
    return 0;


int main(int argc, char **argv)

    GMainLoop *loop;
    int rc;
    guint prop_changed;
    guint iface_added;
    guint iface_removed;

    con = g_bus_get_sync(G_BUS_TYPE_SYSTEM, NULL, NULL);
    if(con == NULL) 
        g_print("Not able to get connection to system bus\n");
        return 1;
    

    loop = g_main_loop_new(NULL, FALSE);

    prop_changed = g_dbus_connection_signal_subscribe(con,
                        "org.bluez",
                        "org.freedesktop.DBus.Properties",
                        "PropertiesChanged",
                        NULL,
                        "org.bluez.Adapter1",
                        G_DBUS_SIGNAL_FLAGS_NONE,
                        bluez_signal_adapter_changed,
                        NULL,
                        NULL);

    iface_added = g_dbus_connection_signal_subscribe(con,
                            "org.bluez",
                            "org.freedesktop.DBus.ObjectManager",
                            "InterfacesAdded",
                            NULL,
                            NULL,
                            G_DBUS_SIGNAL_FLAGS_NONE,
                            bluez_device_appeared,
                            loop,
                            NULL);

    iface_removed = g_dbus_connection_signal_subscribe(con,
                            "org.bluez",
                            "org.freedesktop.DBus.ObjectManager",
                            "InterfacesRemoved",
                            NULL,
                            NULL,
                            G_DBUS_SIGNAL_FLAGS_NONE,
                            bluez_device_disappeared,
                            loop,
                            NULL);

    rc = bluez_adapter_set_property("Powered", g_variant_new("b", TRUE));
    if(rc) 
        g_print("Not able to enable the adapter\n");
        goto fail;
    

    if(argc > 3) 
        rc = bluez_set_discovery_filter(argv);
        if(rc)
            goto fail;
    

    rc = bluez_adapter_call_method("StartDiscovery", NULL, NULL);
    if(rc) 
        g_print("Not able to scan for new devices\n");
        goto fail;
    

    g_main_loop_run(loop);
    if(argc > 3) 
        rc = bluez_adapter_call_method("SetDiscoveryFilter", NULL, NULL);
        if(rc)
            g_print("Not able to remove discovery filter\n");
    

    rc = bluez_adapter_call_method("StopDiscovery", NULL, NULL);
    if(rc)
        g_print("Not able to stop scanning\n");
    g_usleep(100);

    rc = bluez_adapter_set_property("Powered", g_variant_new("b", FALSE));
    if(rc)
        g_print("Not able to disable the adapter\n");
fail:
    g_dbus_connection_signal_unsubscribe(con, prop_changed);
    g_dbus_connection_signal_unsubscribe(con, iface_added);
    g_dbus_connection_signal_unsubscribe(con, iface_removed);
    g_object_unref(con);
    return 0;

您还可以找到有关 StartDiscovery 示例 here 和 SetDiscoveryFilter here 的一些解释。