From freesmartphone.org

Receiving Signals with C

this example listens on a status change (registration to a net provider) and also to changes ot signal strength

/* author: Matze Huber matthias.huber [AT] wollishausen.de */
/* License: GPL Latest */ 
/* less than half of the time could be necessary, if dbus-calls and result-types and their usage were better documented */

#include <stdio.h>
#include <stdlib.h>

#include <dbus/dbus-glib.h>
#include <glib-object.h>
#include <glib.h>


static DBusGConnection *connection = NULL;
DBusGProxy *proxy_dbus = NULL;
GError *error = NULL;


GCallback strength_handler( DBusGProxy *proxy, gint lstrength, gpointer data ) {

	fprintf(stderr, "Strength: %d\n", lstrength);
}


GCallback status_handler( DBusGProxy *proxy, GHashTable *hash, gpointer data ) {

	fprintf(stderr, "status_handler: %s\n", g_value_get_string(g_hash_table_lookup(hash, "provider")));
}


void *getdbus( void *arg ) {
GMainLoop *loop = NULL;

	while ( 1 ) {
		g_type_init();
		loop = g_main_loop_new(NULL, FALSE);
		connection = dbus_g_bus_get(DBUS_BUS_SYSTEM, &error);
		if (!connection) {
			fprintf(stderr, "Failed to open connection to system bus: %s", error->message);
			exit(1);
		}
		proxy_dbus = dbus_g_proxy_new_for_name(connection, "org.freesmartphone.ogsmd", "/org/freesmartphone/GSM/Device", "org.freesmartphone.GSM.Network");

		dbus_g_proxy_add_signal( proxy_dbus, "SignalStrength", G_TYPE_INT, G_TYPE_INVALID, G_TYPE_INVALID );
		dbus_g_proxy_connect_signal( proxy_dbus, "SignalStrength", (GCallback)strength_handler, NULL, NULL );

		dbus_g_proxy_add_signal( proxy_dbus, "Status", dbus_g_type_get_map("GHashTable", G_TYPE_STRING, G_TYPE_VALUE), G_TYPE_INVALID, G_TYPE_INVALID );
		dbus_g_proxy_connect_signal( proxy_dbus, "Status", (GCallback)status_handler, NULL, NULL );
		g_main_loop_run(loop);
		sleep(5);
	}
}



int main( int argc, char *argv[] ) {

	getdbus( NULL );

}