Gdbus服务器和客户端demo

GDBus 是 GNOME 桌面环境中使用的 D-Bus 实现。D-Bus 是一种进程间通信机制，可以在不同进程之间传递消息。

下面是一个简单的 GDBus 服务器和客户端的示例代码：

## 服务器

#include <gio/gio.h>

static gboolean on_handle_echo (GDBusConnection *connection,
                                const gchar     *sender,
                                const gchar     *object_path,
                                const gchar     *interface_name,
                                const gchar     *method_name,
                                GVariant        *parameters,
                                GDBusMethodInvocation *invocation,
                                gpointer         user_data)
{
  gchar *str;
  g_variant_get (parameters, "(&s)", &str);
  g_print ("Received: %s\n", str);
  g_dbus_method_invocation_return_value (invocation, g_variant_new ("(s)", str));
  return TRUE;
}

int main (void)
{
  GMainLoop *loop;
  GDBusNodeInfo *introspection_data;
  GError *error = NULL;

  static const GDBusInterfaceVTable interface_vtable =
  {
    on_handle_echo,
    NULL,
    NULL
  };

  loop = g_main_loop_new (NULL, FALSE);

  introspection_data = g_dbus_node_info_new_for_xml ("<node>"
                                                     "  <interface name='com.example.Echo'>"
                                                     "    <method name='Echo'>"
                                                     "      <arg type='s' name='input' direction='in'/>"
                                                     "      <arg type='s' name='output' direction='out'/>"
                                                     "    </method>"
                                                     "  </interface>"
                                                     "</node>",
                                                     &error);

  if (error != NULL)
  {
    g_printerr ("Error parsing introspection XML: %s\n", error->message);
    g_error_free (error);
    return 1;
  }

  guint registration_id;
  registration_id = g_dbus_connection_register_object (g_bus_get_sync (G_BUS_TYPE_SESSION, NULL, NULL),
                                                        "/com/example/Echo",
                                                        introspection_data->interfaces[0],
                                                        &interface_vtable,
                                                        NULL,
                                                        NULL,
                                                        &error);

  if (error != NULL)
  {
    g_printerr ("Error registering object: %s\n", error->message);
    g_error_free (error);
    return 1;
  }

  g_print ("Listening on /com/example/Echo\n");

  g_main_loop_run (loop);

  g_dbus_connection_unregister_object (g_bus_get_sync (G_BUS_TYPE_SESSION, NULL, NULL), registration_id);
  g_dbus_node_info_unref (introspection_data);
  g_main_loop_unref (loop);

  return 0;
}

这个服务器注册了一个名为 `com.example.Echo` 的 D-Bus 接口，并提供了一个名为 `Echo` 的方法，该方法接受一个字符串参数并返回相同的字符串。

## 客户端

#include <gio/gio.h>

int main (void)
{
  GDBusProxy *proxy;
  GDBusConnection *connection;
  GVariant *result;
  GError *error = NULL;

  connection = g_bus_get_sync (G_BUS_TYPE_SESSION, NULL, &error);
  if (connection == NULL)
  {
    g_printerr ("Failed to get D-Bus connection: %s\n", error->message);
    g_error_free (error);
    return 1;
  }

  proxy = g_dbus_proxy_new_sync (connection,
                                 G_DBUS_PROXY_FLAGS_NONE,
                                 NULL,
                                 "com.example.Echo",
                                 "/com/example/Echo",
                                 "com.example.Echo",
                                 NULL,
                                 &error);

  if (proxy == NULL)
  {
    g_printerr ("Failed to create D-Bus proxy: %s\n", error->message);
    g_error_free (error);
    return 1;
  }

  const gchar *input = "Hello, world!";
  result = g_dbus_proxy_call_sync (proxy,
                                   "Echo",
                                   g_variant_new ("(s)", input),
                                   G_DBUS_CALL_FLAGS_NONE,
                                   -1,
                                   NULL,
                                   &error);

  if (result == NULL)
  {
    g_printerr ("Failed to call Echo method: %s\n", error->message);
    g_error_free (error);
    return 1;
  }

  gchar *output;
  g_variant_get (result, "(s)", &output);
  g_print ("Echo response: %s\n", output);
  g_variant_unref (result);

  g_object_unref (proxy);
  g_object_unref (connection);

  return 0;
}

这个客户端连接到 D-Bus 会话总线上的 `com.example.Echo` 接口，并调用其 `Echo` 方法，将字符串 "Hello, world!" 传递给它并输出响应。

需要注意的是，服务器和客户端代码都需要链接 `gio-2.0` 库。可以使用以下命令编译并链接它们：

gcc -o server server.c $(pkg-config --cflags --libs gio-2.0)
gcc -o client client.c $(pkg-config --cflags --libs gio-2.0)