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Documentation/Maemo 5 Developer Guide/Using Connectivity Components/Maemo Connectivity

Revision as of 13:26, 27 July 2009

Maemo Connectivity

Introduction

The maemo connectivity subsystem is implemented by using known Linux conventions. It resides in the user mode area of Linux, and relies on the Linux kernel through standard C libraries. Wireless LAN or WiMAX is the main channel to the Internet, but dial-up connections through cellular networks are also supported. The only medium to the phone is Bluetooth. The Bluetooth software of maemo is based on BlueZ, which is known as the de-facto implementation of Bluetooth for Linux. D-Bus is used for internal application level message exchange.

Even though the connectivity device drivers are closely related to this subsystem, they are considered to be outside of the scope of this manual.

Components of the maemo connectivity architecture

Maemo connectivity UI - User Interface parts of the connectivity. This includes Connection manager, Control Panel applets and several different dialogs.

Maemo connectivity daemon (ICd) - LibConIC API works together with ICd, handling all Internet Access Points (IAPs). IC daemon handles both WLAN and Bluetooth connections.

OBEX wrapper - Interface to OBEX services. The primary target user of this library is the OBEX gnome-vfs module.

OpenOBEX - Open source implementation of the Object Exchange (OBEX) protocol. For more information on OpenOBEX, see http://triq.net/obex/

BlueZ Bluetooth stack - The de-facto implementation of Bluetooth for Linux. For more information on BlueZ, see http://www.bluez.org

BlueZ D-Bus API - BlueZ accepts commands via D-Bus.

WLAN connectivity daemon - The daemon controlling WLAN connections.

WLAN device driver - Device driver for Wireless LAN (IEEE 802.11g). Kernel driver is composed of two parts: a binary part (closed source) and an open source wrapper, binding the binary to the current Linux kernel.

WiMAX onnectivity daemon - The daemon controlling WiMAX connections.

WiMAX device driver - Device driver for mobile WiMAX (IEEE 802.16e).

Internet Access Points (IAP)

The central concept for maemo Internet connections is the Internet Access Point (IAP), which represents a logical Internet (IP) connection that the user defines. An IAP has a unique name, usually in form of UUID). Among other things, it defines the radio bearer (e.g. WLAN, CSD, GPRS), and usually also the data transfer speed, username, password, proxy server, and the corresponding access point in the Internet or the telephone number of the service provider's modem.

Connectivity Subsystem

This section describes the system decomposition of the Connectivity subsystem. Maemo applications can open Internet connections by using the LibConIC API. The Internet Access subsystem take care of the connection to the phone, if necessary, by using the services of the Phone Access subsystem. If an application needs to gain access to the phone's files, the File selector consults the Phone Access subsystem.

In offline mode, none of the radios must be active. The Device System Management Entity (DSME) of maemo provides information about the transitions to and from the offline mode.

Phone and Internet connections are quite different by nature and behavior. These are introduced in more detail in the following sections.

Phone Access

Phone Access is the subsystem handling connections to a cellular phone. It offers a search utility for finding potential phones and inquiring the services they can offer. This is based on the standard Bluetooth service discovery mechanism. Phone Access also keeps a record of phones that have connected to the device in GConf, and provides a list of them for the user to choose from. Phone Access relies on the Linux Bluetooth implementation called BlueZ. BlueZ offers the Berkeley socket interface to the HCI and to the L2CAP protocol for the user space applications.

In principle, any cellular phone supporting Bluetooth Service Discovery Protocol (SDP), Dial-up Networking profile (DUN) and File Transfer Profile (FTP) can connect to maemo. However, different mobile phones implement varying levels of file transfer services and OBEX. Some products limit access to the Inbox (Object Push), whereas more sophisticated ones make the Gallery and the memory card available. The recent products support the OBEX Capability request for retrieving more specific information about the file system on the phone.

Maemo connects to a phone on an on-demand basis, such as when an application requires a connection. For example, when the Internet browser is about to open a URL, it requests Phone Access to establish a connection to the phone. This causes Phone Access to bind an RFCOMM device to the requested service (in this case DUN) on the phone. In a similar fashion, the File Selector can set up a file transfer connection to the phone using another RFCOMM device. After binding to a service, the application in question can open the local RFCOMM device. Normal file selector access is performed with GnomeVFS layer to get transparent access to phone in the same way as internal flash and MMC are accessed.

The Bluetooth SIM Access (SAP) profile is also needed in maemo to perform WLAN authentication using the EAP-SIM authentication method. In this case, the EAP component asks the BT sap component to get session keys from a GSM/UMTS phone.

Maemo Bluetooth also supports HID (keyboard) and OPP (object push file transfer) profiles.

Internet Access

The Internet Access subsystem manages connections to the Internet over different bearers and is also responsible for the configuration and management of Internet Access Points. Internet Access provides applications with TCP/IP connections. They can be established in the following ways:

• WLAN connection to a wireless access point.
• WiMAX connection to a WiMAX base station.
• Bluetooth connection through phone using Point-to-Point Protocol (PPP) and a cellular modem (in the phone).

For Bluetooth connections, AT commands are applied to establish a PPP link to the cellular modem and the connection to the Internet.

Internet Connectivity Daemon

This section describes how the Internet Connectivity daemon works internally. The following subsections explain the behavior and the decomposition of this component in detail, also covering the interfaces that this component realizes.

Decomposition

If the ICd receives a request to activate or deactivate an IAP, the ICd activates the IAP or, if no IAP has been defined as the default, shows a uI requesting the user to choose one. Depending on the type of the IAP, the ICd uses the appropriate network type plug-in to activate or deactivate specific network interface.

The ICd tracks the applications requesting IAPs by recording their D-Bus base service names. This allows the ICd to detect situations where processes using an IAP have aborted or crashed. The ICd also implements an idle timeout mechanism to shut down the active IAP, if no packets have been sent in a configured amount of time.

Maemo version 3.0 introduced the automatic connection creation feature in the Internet Connectivity Daemon. In other words, the device tries to connect automatically to the saved IAPs, and keep connected as long as possible, unless the idle timeout is set. With this feature, applications like e-mail and RSS reader are always up to date. The device is also always ready for online use, for example, incoming VoIP calls or IM chat. In earlier versions, the Internet connection was automatically closed if no application was using it or when the connection was idle for the period of time defined by the idle timeout configuration parameter.

When the device is not connected, it scans for saved IAPs and tries to connect automatically, taking into account the value defined by the search interval configuration parameter. The search interval can be 5, 10, 30 or 60 minutes; all other values are automatically mapped to "Never". This setup switches off the automatic connection feature. In this case, the device behaves just like the former versions: Connections are created only when applications require it.

Because each application keeps its data updated and provides the always-online feature, the ICd is only responsible for creating connections.

While writing an application making use of the ICd system, keep the following in mind:

• The application must always use the existing available connection.
• As in former versions, if the device is not connected but a connection is required by user interaction, the application must require connection creation using LibConIC API.
• Ensure that the user is aware of updates and can see the time when the data was last updated.
• Ensure that the application registers via LibConIC and listens to signals emitted by the ICd (Connection Created, Lost and Changed), and react as follows:
  • Connection Created: Use the connection and update all data.
  • Connection Lost: Go to an idle state silently and wait until a new connection is created.
  • Connection Changed: Use the new connection.
• Ensure that automatic data updates run in background and silently:
  • Avoid alarming the user with unnecessary banners or dialogs.
  • Ensure that usernames and passwords are saved so that automatic updates can be performed without prompts.
  • During and after updates, ensure that no failures display error notifications.
• The connectivity infrastructure must take care of error situations in a centralized way.

You can switch off the automatic connection creation feature by using offline mode. While in this mode, the configuration parameter for allowing WLAN in offline mode is checked. Depending on the state of this configuration parameter, WLAN IAPs are either enabled or disabled in the offline mode. Also other radios like Bluetooth are normally disabled in the offline mode.

Bluetooth Dial-up Networking

The ICd uses PPP to establish IP connectivity over Bluetooth DUN interfaces. If there already is a different IAP active using Bluetooth DUN, the old IAP is first deactivated. The IAP is activated according the following action sequence:

• The character device used by the Bluetooth DUN device is acquired from btcond. If the device is not available due to gateway not being present, exhaustion of simultaneous Bluetooth connections, or similar, the ICd shows an error message to the user and aborts with a D-BUS error message.
• The ICd starts PPP using the exec family of system calls. It directs PPP to use the acquired Bluetooth DUN device with the dial-up configuration parameters specified for the configured DUN IAP type. If PPP cannot get the connection established, the ICd shows an error message to the user and aborts with a D-BUS error message. When the PPP connection is established, PPP-specific scripts are run. The scripts configuration entries related to dynamic IP connectivity and send a state-change D-BUS message to all interested applications to indicate that the IAP has been established.

If the previously active IAP was not using Bluetooth DUN, it is closed down after establishing the PPP connection.

A Bluetooth DUN is closed down by sending the PPP daemon a SIGINT or SIGTERM signal. This terminates the PPP daemon and removes all routing entries associated with the PPP dial-up interface. The PPP shutdown scripts removes the dynamic IP connection related configuration entries and sends a state change D-BUS message announcing the deactivation of the IAP.

WLAN

For connecting to a WLAN, the ICd needs to associate with the network as well as enable EAP authentication and the DHCP client as needed. Independently of whether an active IAP using WLAN exists, the requested WLAN network is first scanned to ensure that it is available. If the requested network is found and the current IAP is using WLAN, the current IAP is deactivated. WLAN is activated according to the following procedure:

• If the network requires EAP authentication, the EAP authentication procedure is started. While performing the EAP authentication, the EAP software may show GUI dialogs relating to the EAP authentication procedure. When EAP authentication is complete, the EAP software sets security keys for the WLAN network, resulting in state change messages from wlancond. The ICd receives these messages but ignores them and waits for the reply from EAP authentication instead. If the EAP authentication fails, the ICd aborts with a D-Bus error message.
• After the EAP process starts, the ICd instructs wlancond to associate with the WLAN network. Any static security settings relating to pre-shared security keys are also supplied at this point. If it cannot establish a connection to the WLAN network, the ICd aborts with an error.
• Because the DHCP client is a stand-alone program, start it by using exec if the WLAN IAP requires dynamic IP address acquisition. When the DHCP client has obtained an IP address, it configures IP-related parameters, and sends a D-Bus signal to the ICd. If it cannot obtain the IP address lease, the ICd times out, stops the DHCP client and aborts with a D-Bus error message.

LibConIC Library

Internet Connectivity API (in shorter form: Libconic) is an API for applications to manage internet connections on Maemo devices. It was introduced in the first IT OS 2007 release, deprecating the old OSSO IC API (osso-ic-lib). OSSO IC API was conclusively removed in the IT OS 2008 release. For more information on libconic interfaces, see Internet Connectivity API

Libconic is high level and stable object-oriented API suitable for the following purposes:

• requesting Internet connection
• listening for Internet connection status events
• receiving statistics of Internet connection
• getting proxy settings for the current connection
• getting a list of user-saved connections (IAPs)

Application Requirements Before applications can use the Libconic API, they must meet the following requirements:

1. use non-blocking sockets
2. have the system D-BUS running
3. g_type_init() has to be called
4. employ no threading support in the Libconic API

If the application is a standard Hildon application, almost all of these requirements are already fulfilled. LibOSSO context initialization connects the application to both session and system D-BUS buses, g_type_init() is called as a part of gtk_init(), and probably no extra threads are used.

Non-Blocking Sockets Blocking sockets cannot be used because that would also block incoming Connectivity events. Non-blocking sockets should be used in order to receive the events properly. For example, GLib IO Channels with the G_IO_FLAG_NONBLOCK flag provide non-blocking way to use sockets.

With threads, blocking sockets can be used, although Libconic API itself is not thread safe.

System D-BUS Libconic API uses internally system D-BUS for delivering messages to the Connectivity components. Applications must be running normal D-BUS dispatch, watch and timeout monitoring before using the Libconic API. If the GLib mainloop is used, this can be accomplished with
dbus_connection_setup_with_g_main().

N.B. Setting up LibOSSO context connects the application to required D-BUS.

GType Libconic API is GObject-basedm, so in order to get the API working, you must initialize GLib's GType properly. To do that, use g_type_init().

No Multiple Threads Libconic API is not thread-safe. If the applications have threads, use Libconic API only from the same context where GMainloop is running.

Libconic Usage

Requesting for Connection

Libconic is an asynchronous connection API, which heavily relies on GObject signals. Basically this means that GMainloop must be iterated in order to successfully execute connection requests. After the application is set up, use a ConIcConnection object to request a connection:

    gboolean success = FALSE;
    /* Create connection object */
    ConIcConnection *connection = con_ic_connection_new();
    /* Connect signal to receive connection events */
    g_signal_connect(G_OBJECT(connection), "connection-event",
                     G_CALLBACK(my_connection_handler), NULL);
    /* Request connection and check for the result */
    success = con_ic_connection_connect(connection, CON_IC_CONNECT_FLAG_NONE);
    if (!success) g_warning("Request for connection failed");

At this point, the application does not yet have an Internet connection. A successful return from con_ic_connection_connect() means only that the request was successfully dispatched to the Internet Connectivity daemon. When the daemon has a connection ready, the application receives an event (as an GObject signal) indicating that the device is connected. If the connection attempt fails, the application receives a disconnected event with an error describing the reason for the failure.

The connection handler (my_connection_handler() function registered in the previous snippet) could look like this:

static void my_connection_handler(ConIcConnection *connection,
                                  ConIcConnectionEvent *event,
                                  gpointer user_data)
{
    ConIcConnectionStatus status = con_ic_connection_event_get_status(event);
    ConIcConnectionError error;
    const gchar *iap_id = con_ic_event_get_iap_id(CON_IC_EVENT(event));
    const gchar *bearer = con_ic_event_get_bearer_type(CON_IC_EVENT(event));
    switch(status) {
        case CON_IC_STATUS_CONNECTED:
            g_debug("Hey, we are connected to IAP %s with bearer %s!", iap_id, bearer);
            break;
        case CON_IC_STATUS_DISCONNECTING:
            g_debug("We are disconnecting...");
            break;
        case CON_IC_STATUS_DISCONNECTED:
            g_debug("And we are disconnected. Let's see what went wrong...");
            error = con_ic_connection_event_get_error(event);
            switch(error) {
                case CON_IC_CONNECTION_ERROR_NONE:
                    g_debug("Libconic thinks there was nothing wrong.");
                    break;
                case CON_IC_CONNECTION_ERROR_INVALID_IAP:
                    g_debug("Invalid (non-existing?) IAP was requested.");
                    break;
                case CON_IC_CONNECTION_ERROR_CONNECTION_FAILED:
                    g_debug("Connection just failed.");
                    break;
                case CON_IC_CONNECTION_ERROR_USER_CANCELED:
                    g_debug("User canceled the connection attempt");
                    break;
            }
            break;
        default:
            g_debug("Unknown connection status received");
    }
}

Listening for Connection Events

Sometimes the application does not actively start connections but needs to detect if the device is online. The Libconic "automatic events" feature, enabled with "automatic-events" GObject property, can achieve this:

    /* Create connection object */
    ConIcConnection *connection = con_ic_connection_new();
    /* Connect signal to receive connection events */
    g_signal_connect(G_OBJECT(connection), "connection-event",
                     G_CALLBACK(my_connection_handler), NULL);
    /* Set automatic events */
    g_object_set(G_OBJECT(connection), "automatic-events", TRUE, NULL);

When automatic events are turned on, the application receives connected and disconnected events for all Internet connection changes. In addition to this, the application receives an event for the initial connection status. If the device is disconnected, ConIcConnectionEvent with status CON_IC_STATUS_DISCONNECTED is emitted. This event has NULL IAP ID and bearer, because there is no IAP getting disconnected, but the event indicates that the device is offline.

N.B. The main loop must be reiterated in order to receive the event. If you need the connection status information synchronously, you can iterate the main loop yourself:

static void connection_info(ConIcConnection *connection,
                            ConIcConnectionEvent *event,
                            gpointer user_data)
{
    ConIcConnectionStatus status = con_ic_connection_event_get_status(event);
    ConIcConnectionStatus *status_ptr = (ConIcConnectionStatus*)user_data;
    *status_ptr = status;
}
/* ... */
    /* Create connection object and set on automatic events (see previous snippet) ... */
    static ConIcConnectionStatus status = 0xFFFF;
    ConIcConnection *connection = con_ic_connection_new();
    g_signal_connect(G_OBJECT(connection), "connection-event",
                     G_CALLBACK(connection_info), &status);
    g_object_set(G_OBJECT(Connection), "automatic-events", TRUE, NULL);
    /* Iterate main loop for the first connection event */
    while (status == 0xFFFF) g_main_context_iteration(NULL, TRUE);
    if (status == CON_IC_STATUS_CONNECTED)
        g_debug("We are connected!");
    else
        g_debug("We are not connected!");

Receiving Statistics of Connection

To receive statistics of the current Internet connection, use the con_ic_connection_statistics() function and the corresponding event handler. You can retrieve statistics for a specified IAP or just for the current default connection. Note that currently the Internet Connectivity daemon provides only one Internet connection at a time, so the best option is to leave IAP ID NULL.

static void connection_statistics(ConIcConnection *connection,
                                  ConIcStatisticsEvent *event,
                                  gpointer user_data)
{
    g_debug("Here are all kind of nice statistics about the connection:");
    g_debug("Time active: %u, signal strength: %u, received packets: %llu, "
            "sent packets: %llu, received bytes: %llu, sent bytes: %llu",
            con_ic_statistics_event_get_time_active(event),
            con_ic_statistics_event_get_signal_strength(event),
            con_ic_statistics_event_get_rx_packets(event),
            con_ic_statistics_event_get_tx_packets(event),
            con_ic_statistics_event_get_rx_bytes(event),
            con_ic_statistics_event_get_tx_bytes(event));
}
/* ... */
    /* ConIcConnection object named "connection" has already been created */
    g_signal_connect(G_OBJECT(connection), "statistics",
                     G_CALLBACK(connection_statistics), NULL);
    if (!con_ic_connection_statistics(connection ,NULL))
        g_warning("Requesting connection statistics failed!");

Getting Proxy Settings

Libconic allows you to set up Internet connection proxy settings for various protocols. The first step is to discover the current proxy mode by using the con_ic_connection_get_proxy_mode() function. Next, use the following functions to get the actual proxy settings:

• If proxy mode is CON_IC_PROXY_MODE_NONE, do not use any proxies.
• If proxy mode is CON_IC_PROXY_MODE_MANUAL, use the following functions to query proxy settings:
  • con_ic_connection_get_proxy_host() to get the proxy host
  • con_ic_connection_get_proxy_port() to get the proxy port
  • con_ic_connection_get_proxy_ignore_hosts() to get a list of hosts for which the proxy should not be used.
• If proxy mode is CON_IC_PROXY_MODE_AUTO, use
  con_ic_connection_get_proxy_autoconfig_url() to get a proxy auto configuration URL.
  • Use of auto configuration URL is explained in Wikipedia

In this example, the "connection-event" handler is modified to print HTTP proxy settings when establishing connection:

static void my_connection_handler(ConIcConnection *connection,
                                  ConIcConnectionEvent *event,
                                  gpointer user_data)
{
    ConIcConnectionStatus status = con_ic_connection_event_get_status(event);
    GSList *ignore_hosts;

    if (status == CON_IC_STATUS_CONNECTED) {
        g_debug("We are connected! \
Let's see what kind of settings we have for HTTP proxy...");

        /* Do things based on specified proxy mode */
        switch (con_ic_connection_get_proxy_mode(connection)) {

            case CON_IC_PROXY_MODE_NONE:
                g_debug("No proxies defined, it is direct connection");
                break;

            case CON_IC_PROXY_MODE_MANUAL:
                g_debug("HTTP proxy %s:%d in use",
                        con_ic_connection_get_proxy_host(connection, CON_IC_PROXY_PROTOCOL_HTTP),
                        con_ic_connection_get_proxy_port(connection, CON_IC_PROXY_PROTOCOL_HTTP));

                g_debug("List of hosts, for which proxy should not be used:");
                ignore_hosts = con_ic_connection_proxy_ignore_hosts(connection);
                for (GSList *iter = ignore_hosts; iter != NULL; iter = g_slist_next(iter))
                {
                    g_debug("%s", (gchar *)iter->data);
                    g_free(iter->data);
                }
                g_slist_free(ignore_hosts);
                break;

            case CON_IC_PROXY_MODE_AUTO:
                g_debug("Proxy auto-config URL %s should be used",
                        con_ic_connection_get_proxy_autoconfig_url(connection));
                break;
        }
    }
}

Proxy functions also exist for each individual protocol (like
con_ic_connection_get_proxy_ftp_host()), but these functions are deprecated. Avoid them in newly-written code.

Getting List of User-Saved Connections

To query all user-saved connections (IAPs), use the con_ic_connection_get_all_iaps() function. The function returns simply a singly linked list of ConIcIap objects:

    /* ConIcConnection object named "connection" has already been created */
    GSList *saved_iaps = con_ic_connection_get_all_iaps(connection);
    g_debug("The following connections have been saved by the user:");
    for (GSList *iter = saved_iaps; iter != NULL; iter = g_slist_next(iter)) {
        /* Get IAP object and print some information about it */
        ConIcIap *iap = (ConIcIap *)iter->data;
        g_debug("Connection %s called '%s' using bearer %s",
                con_ic_iap_get_id(iap), con_ic_iap_get_name(iap),
                con_ic_iap_get_bearer_type(iap));
        /* We unref the IAP object as we are not going to use it anymore */
        g_object_unref(iap);
    }
    g_slist_free(saved_iaps);

Porting Application from OSSO IC API to Libconic

• If the application does not have GType, GLib or D-BUS configured, set them up:

      DBusConnection *system_dbus;
      GMainloop *main_loop;
      g_type_init();
      main_loop = g_main_loop_new(NULL, FALSE);
      system_dbus = dbus_bus_get(DBUS_BUS_SYSTEM, NULL);
      dbus_connection_setup_with_g_main(system_dbus, NULL);

• Include the correct header file:

      #include <osso-ic.h>
      ===>
      #include <conic.h>

• Set up ConIcConnection object and "connection-event" handler instead of osso_iap_cb_t callback:

      static void my_connection_cb(struct iap_event_t *event, void *arg)
      {
      /* ... */
      }
      /* ... */
          osso_iap_cb(my_connection_cb);
      ===>
      static void my_connection_cb(ConIcConnection *connection,
                                   ConIcConnectionEvent *event,
                                   gpointer user_data)
      {
      /* ... */
      }
      /* ... */
          ConIcConnection *connection = con_ic_connection_new();
          g_signal_connect(G_OBJECT(connection), "connection-event",
                           G_CALLBACK(my_connection_cb), app_data);

• Manage connections through ConIcConnection API instead of
  osso_iap_connect() and osso_iap_disconnect():

      osso_iap_connect(OSSO_IAP_ANY, OSSO_IAP_REQUESTED_CONNECT, app_data);
      osso_iap_disconnect(iap_name, app_data);
      ===>
      con_ic_connection_connect(connection, CON_IC_CONNECT_FLAG_NONE);
      con_ic_connection_disconnect(connection);

• Request statistics with con_ic_connection_statistics() instead of
  osso_iap_get_statistics().
• List all available IAPs with con_ic_connection_get_all_iaps() instead of
  osso_iap_get_configured_iaps().
• Configure autoconf to use Libconic instead of OSSO IC API:

      PKG_CHECK_MODULES(OSSOIC, osso-ic)
      AC_SUBST(OSSOIC_CFLAGS)
      AC_SUBST(OSSOIC_LIBS)
      ===>
      PKG_CHECK_MODULES(CONIC, conic)
      AC_SUBST(CONIC_CFLAGS)
      AC_SUBST(CONIC_LIBS)

• In debian/control file "Build-Depends" section, depend on libconic0-dev instead of osso-ic-dev.

Bluetooth Libraries

This section explains how maemo Bluetooth libraries work internally. The following subsections explain the behavior and the decomposition of the Bluetooth library components in detail.

Libgwobex

Libgwobex provides access to libopenobex functionality by providing a
helper/wrapper interface. Libopenobex is explained in detail in the following section.

The interface to libgwobex is available at GW OBEX Library Documentation.

Creating Connection

The connection with libgwobex is established using the gw_obex_setup_dev function, setting up the connection. gw-obex.h

#define OBEX_FTP_UUID \
        "\xF9\xEC\x7B\xC4\x95\x3C\x11\xD2\x98\x4E\x52\x54\x00\xDC\x9E\x09"
#define OBEX_FTP_UUID_LEN 16

/* ... */

GwObex* gw_obex_setup_dev (const gchar * device, const gchar * uuid, gint uuid_len,
                           GMainContext * context, gint * error )

The following code snippet illustrates how to open a handle using gw_obex_setup_dev.

if (ctx->rfcomm_dev) {
        if (ctx->use_ftp)
                ctx->obex = gw_obex_setup_dev(ctx->rfcomm_dev,
                        OBEX_FTP_UUID, OBEX_FTP_UUID_LEN,
                        NULL, &err);
        else
                ctx->obex = gw_obex_setup_dev(ctx->rfcomm_dev, NULL,
                        0, NULL, &err);

        if (ctx->obex == NULL)
                printf("OBEX setup failed: %s\n", response_to_string(err));
}

In this example, ctx->rfcomm_dev points to a string containing the device node name (e.g. /dev/rfcomm0). ctx->use_ftp dictates whether to set up standard folder browsing services. If use_ftp is untrue, then INBOX is connected.

Closing Connection

To close a gwobex connection, use the following function: gw-obex.h

void gw_obex_close ( GwObex * ctx );

The following code demonstrates this usage.

if (ctx->obex) {
        gw_obex_close(ctx->obex);
        ctx->obex = NULL;
}

If ctx->obex is not NULL, it is simply passed as an argument to gw_obex_close().

Using Connection

The libgwobex library provides general file handling functionality, including reading directory structure, browsing in different folders and getting files.

To read entries from an opened directory, use the following function: gw-obex.h

gboolean gw_obex_read_dir (GwObex * ctx,
                           const gchar * dir,
                           gchar ** buf,
                           gint * buf_size,
                           gint * error );

gw_obex_read_dir reads an entry from the selected folder and returns the result in the buf argument given to the function.

gboolean ret;
/* ... */
ret = gw_obex_read_dir(ctx->obex, dir, buf, buf_size, err);

This reads an entry from the directory dir (char *) and returns it in buf (char **).

To change the current directory, use the following function: gw-obex.h

gboolean gw_obex_chdir (GwObex * ctx, const gchar * dir, gint * error );

which changes the directory of the FTP connection. Below is a code example using this function.

/* Ignore parent dir pointers */
if (g_str_equal(name, ".."))
        return TRUE;

if (!gw_obex_chdir(ctx->obex, name, err)) {
        printf("Could not chdir to %s\n", name);
        return FALSE;
}

To retrieve files over the OBEX connection, use the gw_obex_get_file function: gw-obex.h

gboolean gw_obex_get_file (GwObex * ctx,
                           const gchar * local,
                           const gchar * remote,
                           const gchar * type,
                           gint * error);

gw_obex_get_file uses the ctx context for retrieving the remote file to local file.

gboolean ret;
ret = gw_obex_get_file(ctx->obex, name, name, err);

Using the libwobex wrapper directly allows you to perform many more functions. For more information, see the [hhttp://maemo.org/api_refs/5.0/beta/osso-gwobex/ API document].

Libopenobex

The LibOpenOBEX library implements a generic OBEX Session Protocol, but not the OBEX Application Framework. OBEX is a protocol designed to allow data interchanging between different kinds of connections (e.g. Bluetooth, IrDA). For more information on the OBEX protocol, see http://www.irda.org; select the Developer->Specifications category. OBEX resembles the HTTP protocol, expect for a few differences:

• Transports: While HTTP is normally layered above a TCP/IP connection, OBEX is usually transported over IrLAP/IrLMP/Tiny TP (on IrDA) or over Baseband/Link Manager/L2CAP/RFCOMM (on Bluetooth).
• Binary transmissions: OBEX communicates using binary transmissions, as HTTP is transmitted in a human-readable XML-based format.
• Session support: HTTP is stateless, while OBEX maintains the connection.

For more information on OBEX, see the summary available at
http://en.wikipedia.org/wiki/OBEX.

For libopenobex code samples, see
http://openobex.triq.net/downloads; the samples are in the example apps package.

Using BlueZ D-Bus API

The BlueZ system exports a D-Bus API that can be employed instead of OSSO Bluetooth tools. See the following documents:

• BlueZ D-Bus API documentation
• BlueZ Wiki

Connectivity UI

UI Components

Connectivity UI contains various dialogs and other components used to control the connectivity. The different UI parts are:

• Connection manager
• Connectivity dialogs
• Status bar applets
• Control panel applet
• Bluetooth UIs

The connectivity dialogs are invoked by D-Bus method calls, so for example the ICd is using these D-Bus method calls for showing dialogs when they are needed. The next section specifies the D-Bus API of maemo connectivity UI.

D-Bus Connectivity UI Interface

If the user must provide information about the IAP that the system is about to connect to, you can use the following method:

Service:           com.nokia.icd_ui
Interfaces:        com.nokia.icd_ui
Object paths:      /com/nokia/icd_ui

The Internet Connectivity UIs implement the following D-Bus API used by the ICd and EAP.

Method:            show_conn_dlg
Parameters:        none
Return parameters: none
Errors:            com.nokia.icd_ui.error.flight_mode:
                   Flight mode enabled, dialog not shown
Description:       Shows the Connect Dialog where the user can choose an IAP.

Method:            show_disconnect_dlg
Parameters:        none

Return Parameters: none
Errors:            com.nokia.icd_ui.error.flight_mode:
                   Flight mode enabled, dialog not shown

Description:       Shows the disconnect dialog.

Method:            show_retry_dlg
Parameters:        1. string  Bluetooth address of the device used with SAP
                   2. string  Name of the connection attempt error which
                               selects the retry dialog type.

Return Parameters: none
Errors:            com.nokia.icd_ui.error.flight_mode:
                   Flight mode enabled, dialog not shown

Description:       Shows the retry dialog.

Method:            show_change_dlg
Parameters:        1. string  Name of the currently active IAP
                   2. string  Name of the IAP to be activated

Return Parameters: none
Errors:            com.nokia.icd_ui.error.flight_mode:
                   Flight mode enabled, dialog not shown

Description:       Shows the Change IAP Dialog

Method:            show_passwd_dlg
Parameters:        1. string  Username supplied by ICd
                   2. string  Password supplied by ICd
                   3. string  Name of the IAP

Return Parameters: none
Errors:            com.nokia.icd_ui.error.flight_mode:
                   Flight mode enabled, dialog not shown

Description:       Shows the username/password dialog.

Method:            show_gtc_dlg
Parameters:        1. string  GTC challenge string

Return Parameters: none
Errors:            com.nokia.icd_ui.error.flight_mode:
                   Flight mode enabled, dialog not shown

Description:       Shows EAP GTC challenge dialog.

Method:            show_mschap_change_dlg
Parameters:        1. string  Supplied username
                   2. string  Old password that is to be changed
                   3. string  Name of the IAP

Return Parameters: none
Errors:            com.nokia.icd_ui.error.flight_mode:
                   Flight mode enabled, dialog not shown

Description:       Shows EAP MSCHAPv2 change password dialog.

Method:            show_private_key_passwd_dlg
Parameters:        1. uint32  The private key ID

Return Parameters: none
Errors:            com.nokia.icd_ui.error.flight_mode:
                   Flight mode enabled, dialog not shown

Description:       Shows EAP private key password dialog

Method:            show_server_cert_dlg
Parameters:        1. string  Certificate name
                   2. string  Certificate serial
                   3. boolean  TRUE if certificate is expired, FALSE otherwise
                   4. boolean  TRUE if root CA is unknown or self-signed
                                certificate, FALSE otherwise

Return Parameters: none
Errors:            com.nokia.icd_ui.error.flight_mode:
                   Flight mode enabled, dialog not shown

Description:       Shows server certificate error and expiration dialogs.
                   If both boolean arguments are false, the error dialog is
                   shown. If either or both boolean arguments are TRUE, the
                   expiration dialog is shown instead.

Method:            strong_bt_req
Parameters:        1. string  Bluetooth address of the device to pair with
                   2. boolean  TRUE if strong authentication enabled, FALSE
                                if strong authentication is disabled

Return Parameters: none
Errors:            com.nokia.icd_ui.error.flight_mode:
                   Flight mode enabled, dialog not shown

Description:       Requests strong (16 digit) BT PIN dialog for a BT device

Method:            show_sim_pin_dlg
Parameters:        1. string  Bluetooth address of the device used with SAP
                   2. boolean  TRUE if PIN was incorrect and retry dialog
                                should be displayed before asking PIN. FALSE
                                if this is the first PIN request.

Return Parameters: none
Errors:            com.nokia.icd_ui.error.flight_mode:
                   Flight mode enabled, dialog not shown

Description:       Shows SIM PIN dialog

The code example for the application to show the connect dialog using show_conn_dlg is following. Note the use of the macro.

#include <osso-ic-ui-dbus.h>
/* ... */
/* in our code somewhere, where we need the Connect Dialog*/
DBusMessage *uimsg;
/* construct the message for Connect Dialog request*/
uimsg =
  dbus_message_new_method_call(ICD_UI_DBUS_SERVICE,
                             ICD_UI_DBUS_PATH,
                           ICD_UI_DBUS_INTERFACE,
                         /*macro for show_conn_dlg */
                               ICD_UI_SHOW_CONNDLG_REQ);
/* send the message */
reply =
  dbus_connection_send_with_reply_and_block(connection,
                                    uimsg,
                                   reply_timeout,
                                   &error);
if (reply == NULL) {
    DLOG_ERR("Failed to show connect dialog: %s", uierror.message);
    dbus_error_free(&uierror);
}
dbus_message_unref(uimsg);
dbus_message_unref(reply);
/* ... */

The signals emitted from com.nokia.icd_ui interface are listed below.

Signal:        disconnect
Parameters:    1. boolean  TRUE if "disconnect" pressed, FALSE if "cancel"

Description:   Signal emitted from UI when disconnect dialog has been closed.

Signal:        retry
Parameters:    1. string  The IAP that is to be retried
               2. boolean  TRUE if "retry" pressed, FALSE if "cancel"

Description:   Signal emitted from UI when the retry dialog has been closed.

Signal:        change
Parameters:    1. string  Old IAP to change from
               2. string  New IAP to change to
               3. boolean  Change to the new IAP If TRUE, keep old if FALSE

Description:   Signal emitted from UI when change connection dialog has
                been closed.

Signal:        passwd
Parameters:    1. string  Username supplied or modified by the user
               2. string  Password supplied or modified by the user
               3. string  IAP name
               4. boolean  TRUE if "ok" pressed, FALSE if "cancel"

Description:   Signal emitted from UI when the username/password dialog has
               been closed

Signal:        gtc_response
Parameters:    1. string  Response to the given challenge or empty string
                           if cancelled
               2. boolean  TRUE if "ok" pressed, FALSE if "cancel"

Description:   Signal emitted from UI when the EAP GTC challenge dialog has
               been closed.

Signal:        mschap_change
Parameters:    1. string  Supplied username
               2. string  The new password or empty string if cancelled
               3. string  IAP name
               4. boolean  TRUE if "ok" pressed, FALSE if "cancel"

Description:   Signal emitted from UI when the MSCHAPv2 password has been
               changed

Signal:        private_key_passwd
Parameters:    1. uint32  The id of the private key
               2. string  Password for the private key or empty string if none
               3. boolean  TRUE if "ok" pressed, FALSE if "cancel"

Description:   Signal emitted from UI when the private key password dialog
               has been closed

Signal:        server_cert
Parameters:    1. boolean  TRUE if strong PIN entered, FALSE if strong
                            PIN dialog was canceled

Description:   Signal emitted from UI when the server certificate error
               dialog has been closed

Signal:        strong_bt
Parameters:    1. boolean  TRUE if strong PIN entered, FALSE if strong
                            PIN dialog was cancelled

Description:   Signal emitted from UI when the strong (16 digit) BT PIN
               has been entered

Signal:        sim_pin
Parameters:    1. string  SIM PIN code or empty string if  cancelled
               2. boolean  TRUE if "ok" pressed, FALSE if "cancel"

Description:   Signal emitted from UI when the SIM PIN has been entered.

Bluetooth DBUS UI dialogs

conbtdialogs-dbus.h

/** 
  Example of use (command line):
  
  dbus-send -system -print-reply \
    -dest='com.nokia.icd_ui' /com/nokia/bt_ui \
    com.nokia.bt_ui.show_send_file_dlg \
    array:string:file:///home/user/MyDocs/.documents/testing.txt
    
  dbus-send -system -print-reply \
    -dest=com.nokia.bt_ui  /com/nokia/bt_ui 
    com.nokia.bt_ui.show_search_dlg \
    string: string: array:string: boolean:true
*/

#ifndef CONBTDIALOGS_DBUS_H
#define CONBTDIALOGS_DBUS_H

#ifdef __cplusplus
extern "C" {
#endif

/** Conbtdialogs service, resides in system dbus */
#define CONBTDIALOGS_DBUS_SERVICE                "com.nokia.bt_ui"
/** Conbtdialogs interface */
#define CONBTDIALOGS_DBUS_INTERFACE                "com.nokia.bt_ui"
/** Conbtdialogs path */
#define CONBTDIALOGS_DBUS_PATH                        "/com/nokia/bt_ui"

/** 
  Show send file dialog
 
  Arguments:
  
  uris: DBUS_TYPE_ARRAY                Array of strings representing the URIs of the
                                files to send.
  
  Returns:
  
  DBUS_TYPE_BOOLEAN             TRUE, if dialog was shown successfully.
 */
#define CONBTDIALOGS_SEND_FILE_REQ                "show_send_file_dlg"

/** 
  File sending result signal
 
  Arguments:
  
  success: DBUS_TYPE_BOOLEAN        TRUE, if all files were sent successfully or
                                FALSE, if error occurred or sending was 
                                canceled.
 */
#define CONBTDIALOGS_SEND_FILE_SIG                "send_file"

/** 
  Show BT device search dialog
 
  Arguments:
  
  major_class: DBUS_TYPE_STRING To set filtering based on major_class or
                                "". Possible major class values are:
                                
                                "miscellaneous", "computer", "phone", 
                                "access point", "audio/video", 
                                "peripheral", "imaging", "wearable",
                                "toy" and "uncategorized".
  
  minor_class: DBUS_TYPE_STRING To set filtering based on minor_class or "".
                                Possible minor class values are:
                        
                                - Minor classes for "computer": 
                                  "uncategorized", "desktop", "server",
                                  "laptop", "handheld", "palm", "wearable"

                                - Minor classes for "phone": "uncategorized",
                                  "cellular", "cordless", "smart phone",
                                  "modem", "isdn"
  
  service_classes: DBUS_TYPE_ARRAY To set filtering based on service classes.
                                   Supported classes include "positioning", 
                                   "networking", "rendering", "capturing",
                                   "object transfer", "audio", "telephony", 
                                   "information". Can be empty list, when no
                                   service class filtering is performed.
  
  bonding: DBUS_TYPE_STRING     Bonding mode for found and selected device:
                                
                                "require" for requiring a bonding from a
                                selected device (i.e. bond device if it has not
                                been bonded before). 
                                
                                "force" to always bond (i.e. device will be
                                bonded even if bonded before).
                                
                                Any other string will allow to search and
                                select device without bonding it.
                                
  Returns:
  
  DBUS_TYPE_BOOLEAN             TRUE, if dialog was shown successfully.
 */
#define CONBTDIALOGS_SEARCH_REQ                 "show_search_dlg"

/** 
  Bluetooth search result signal
 
  Arguments:
  
  address: DBUS_TYPE_STRING     Bluetooth address of the selected device, or ""
                                if search dialog was cancelled.
  
  name: DBUS_TYPE_STRING        Name of the device.
  
  icon: DBUS_TYPE_STRING        Logical name for the icon describing the 
                                device.
  
  major_class: DBUS_TYPE_STRING Major class of the device.
  
  minor_class: DBUS_TYPE_STRING Minor class of the device.
  
  trusted: DBUS_TYPE_BOOLEAN    Defines whether the device is marked as a trusted device.
  
  services: DBUS_TYPE_ARRAY     List of strings describing the service classes
                                and SDP-based services provided by the device.
 */
#define CONBTDIALOGS_SEARCH_SIG                 "search_result"

/**
  Bluetooth UI Library for maemo

  Copyright (C) 2006 Nokia. All rights reserved.
  
  This sample demonstrates the use of conbtdialogs API and especially 
  send_file function. Compile the program with conbtdialogs and dbus:
  
  gcc -Wall `pkg-config -libs -cflags dbus-glib-1 conbtdialogs` \
-o send_file conbtdialogs_send_file.c
  
  Run with list of URLS:
  
  ./send_file file:///home/user/MyDocs/.sounds/Everyday.mp3
*/

#define DBUS_API_SUBJECT_TO_CHANGE

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

DBusGConnection *connection = NULL;
GMainLoop *mainloop = NULL;

static gboolean initialize(void)
{
    GError *error = NULL;

    g_type_init ();

    /* Create main loop */
    mainloop = g_main_loop_new(NULL, TRUE);
    if ( mainloop == NULL ) return FALSE;

    /* Create DBUS connection */
    connection = dbus_g_bus_get(DBUS_BUS_SYSTEM, &error);

    if (connection == NULL )
    {
        g_print ("Error: %s\n", error->message);
        g_clear_error (&error);
        return FALSE;
    }

    return TRUE;
}

static gboolean uninitialize(void)
{
    /* Quit main loop and unref it */
    if (mainloop != NULL)
    {
        g_main_loop_quit(mainloop);
        g_main_loop_unref(mainloop);
    }

    return TRUE;
}

static DBusHandlerResult file_sent_signal ( DBusConnection *connection,
                                            DBusMessage *message,
                                            void *data )
{
    gboolean success = FALSE;

    /* check signal */
    if (!dbus_message_is_signal(message,
                                CONBTDIALOGS_DBUS_INTERFACE,
                                CONBTDIALOGS_SEND_FILE_SIG))
        return DBUS_HANDLER_RESULT_NOT_YET_HANDLED;

    /* get args */
    if ( !dbus_message_get_args ( message, NULL,
                                  DBUS_TYPE_BOOLEAN, &success,
                                  DBUS_TYPE_INVALID ) )
      return DBUS_HANDLER_RESULT_NOT_YET_HANDLED;

    /* print if file sending was success or failure */
    g_print ( "File sending was a " );

    if (success) g_print("success\n"); else g_print("failure\n");
    dbus_connection_close(connection);
    uninitialize();

    return DBUS_HANDLER_RESULT_HANDLED;
}

gint main(gint argc, gchar **argv)
{
    GError *error = NULL;
    gchar **files = NULL;
    gint idx = 0;
    DBusGProxy *proxy;
    DBusConnection *sys_conn;
    gchar *filter_string = NULL;

    if (argc < 2) return 1;

    if (initialize() == FALSE) {
        uninitialize();
        return 1;
    }

    /* Copy urls to GLib compatible char array */
    files = g_new0(gchar*, argc);

    for (idx = 1; idx < argc; idx++)
        files[idx-1] = g_strdup(argv[idx]);

    files[argc-1] = NULL;

    /* Open connection for btdialogs service */
    proxy = dbus_g_proxy_new_for_name(connection,
                                      CONBTDIALOGS_DBUS_SERVICE,
                                      CONBTDIALOGS_DBUS_PATH,
                                      CONBTDIALOGS_DBUS_INTERFACE);

    /* Send send file request to btdialogs service */
    if (!dbus_g_proxy_call(proxy, CONBTDIALOGS_SEND_FILE_REQ,
                           &error,
                           G_TYPE_STRV, files, G_TYPE_INVALID,
                           G_TYPE_INVALID))
    {
        g_print("Error: %s\n", error->message);
        g_clear_error(&error);
        g_strfreev (files);
        g_object_unref(G_OBJECT(proxy));
        uninitialize();
        return 1;
    }
    g_strfreev (files);
    files = NULL;

    g_object_unref(G_OBJECT(proxy));

    /* Now wait for file sent signal, use low level bindings as glib 
       bindings require signal marshaller registered */
    sys_conn = dbus_bus_get(DBUS_BUS_SYSTEM, NULL);
    g_assert(dbus_connection_add_filter(sys_conn,
                                        file_sent_signal,
                                        NULL,
                                        NULL ));
    filter_string =
       g_strdup_printf ("type='signal',interface='%s'", CONBTDIALOGS_DBUS_INTERFACE);

    dbus_bus_add_match(sys_conn, filter_string, NULL);
    dbus_connection_unref(sys_conn);

    /* Run mainloop */
    g_main_loop_run(mainloop);

    return 0;
}

Location

Location framework provides a library called liblocation which is used for developing location aware applications in Fremantle. Liblocation supports internal GPS, network based methods and external bluetooth GPS.

Using liblocation

To start implementing applications using liblocation API, you have to include the following headers.

#include <location/location-gps-device.h>
#include <location/location-gpsd-control.h>

Liblocation has two public GObjects. LocationGPSDControl is used for starting and stopping of location services, setting location method and interval, and listening for errors. LocationGPSDevice has information about device status and contains the actual fix when one exists. The two GObjects are initiated as follows.

LocationGPSDControl *control = location_gpsd_control_get_default();
LocationGPSDevice *device = g_object_new(LOCATION_TYPE_GPS_DEVICE, NULL);

Location methods

Liblocation supports the following location methods which are defined in location-gpsd-control.h.

• LOCATION_METHOD_USER_SELECTED: Liblocation will choose the best possible location method based on location settings in control panel. If both gps and network positioning are enabled, then this will equal to ACWP+AGNSS. Choose this method if you don't have any special needs.
• LOCATION_METHOD_CWP - Complementary Wireless Positioning: The least accurate method with latitude and longitude of the fix pointing to the center of current country and horizontal accuracy being roughly radius of the country. SIM card is needed for CWP method.
• LOCATION_METHOD_ACWP - Assisted Complementary Wireless Positioning: A method where device is located based on cellular base station, device is registered to. SIM card and a network connection is needed for ACWP method. If no network connection is available, this equals to CWP. Application might receive CWP fixes before base station information from external location server is fetched.
• LOCATION_METHOD_GNSS - Global Navigation Satellite System: A method for using GPS receiver. Typically time for the first fix is significantly longer than with AGNSS. Neither SIM card nor network connection is needed for GNSS method, and GNSS can even be used in offline mode.
• LOCATION_METHOD_AGNSS - Assisted Global Navigation Satellite System A method for using GPS receiver with assistance data from external location server. A SIM card and a network connection is needed for AGNSS method. If no network connection or SIM card is available, this equals to GNSS.

Location resources are shared between applications, and applications can request different location methods. Fixes for all requested methods are sent for all applications listening to liblocation "changed" signal, therefore application should judge whether fix it is receiving, is one that it needs. See LocationGPSDeviceFix chapter for discussion.

If device is set for bluetooth GPS from control panel, it can used for locationing via USER_SELECTED, AGNSS and GNSS methods. In this case AGNSS and GNSS do not differ, because assistance server cannot be utilized.

Device caches cell information for ACWP and satellite information for AGNSS. Hence if a non-assisted location method is used immediately after it's assisted counterpart, it will probably work as the assisted one.

Location method is set as LocationGPSDControl's "preferred-method" property. Several methods can be given by bitwise or'ing the method identifiers:

g_object_set(G_OBJECT(control), "preferred-method", LOCATION_METHOD_ACWP | LOCATION_METHOD_AGNSS, NULL);

Here is table that summarizes differences between the methods. Accuracy refers to horizontal accuracy of the fix.

Location intervals

Liblocation supports a default interval and intervals of 1, 2, 5, 10, 20, 30, 60 and 120 seconds between fixes. These are defined in location-gpsd-control.h. Default interval means that several fixes are only sent when device's position changes, therefore it is a good choice for power consumption aware applications, and should be used if application doesn't have any special needs.

Due to the fact that location resources are shared between applications, setting interval to e.g. 5 seconds doesn't necessarily guarantee that you are getting fixes at 5 second interval, but the maximum time between fixes is 5 seconds.

Location interval is set as LocationGPSDControl's "preferred-interval" property:

g_object_set(G_OBJECT(control), "preferred-interval", LOCATION_INTERVAL_60S, NULL);

LocationGPSDevice and LocationGPSDeviceFix

LocationGPSDevice object has the following public fields:

• gboolean online: Whether there is a connection to the hardware
• LocationGPSDeviceStatus status: Status of the device
• LocationGPSDeviceFix *fix: The actual fix (latitude, longitude, etc)
• int satellites_in_view: Number of satellites in view
• int satellites_in_use: Number of satellites in use
• GPtrArray *satellites: Array of satellites
• LocationCellInfo *cell_info: Information about cell the device is connected to

The most useful field is naturally "fix" which contains position and movement of the device and accuracies for them. LocationGPSDeviceFix fields are listed below. In parenthesis there is a identifier which can be bitwisely anded with "fields" field, to see whether corresponding field is set.

• LocationGPSDeviceMode mode: The mode of the fix
• guint32 fields: A bitfield representing what fields contain valid data
• double time: The timestamp of the update (LOCATION_GPS_DEVICE_TIME_SET)
• double ept: Time accuracy
• double latitude: Fix latitude (LOCATION_GPS_DEVICE_LATLONG_SET)
• double longitude: Fix longitude (LOCATION_GPS_DEVICE_LATLONG_SET)
• double eph: Horizontal position accuracy
• double altitude: Fix altitude in meters (LOCATION_GPS_DEVICE_ALTITUDE_SET)
• double epv: Vertical position accuracy
• double track: Direction of motion in degrees (LOCATION_GPS_DEVICE_TRACK_SET)
• double epd: Track accuracy
• double speed: Current speed in km/h (LOCATION_GPS_DEVICE_SPEED_SET)
• double eps: Speed accuracy
• double climb: Current rate of climb in m/s (LOCATION_GPS_DEVICE_CLIMB_SET)
• double epc: Climb accuracy

An application receiving a fix cannot know if the fix is a result from location method it requested. Therefore application should study whether fix is accurate enough to satisfy application's needs. This can be done by inspecting "eph" field, which is fix's horizontal accuracy in centimeters. Typical values for horizontal accuracies can be seen in the location methods table. If accuracy is not known, it has a value of NaN.

Liblocation signals and callbacks

The most useful signal in liblocation is LocationGPSDevice's "changed" signal, which is emitted everytime a new fix is received. LocationGPSDControl has an "error" signal which is emitted in case of an error. You can connect to these signals in the usual way:

g_signal_connect(control, "error", G_CALLBACK(on_error), user_data);
g_signal_connect(device,  "changed", G_CALLBACK(on_changed), user_data);

Below is an example for these signals' callbacks.

static void on_error(LocationGPSDControl *control, gpointer user_data)
{ 

g_debug("Location error");

}

static void on_changed(LocationGPSDevice *device, gpointer user_data)
{
	if (!device)
		return;

	if (device->fix) {
		if (device->fix->fields & LOCATION_GPS_DEVICE_LATLONG_SET)
			g_debug("lat = %f, long = %f", device->fix->latitude, device->fix->longitude);

		if (device->fix->fields & LOCATION_GPS_DEVICE_ALTITUDE_SET)
			g_debug("alt = %f", device->fix->altitude);
    
		g_debug("horizontal accuracy: %f meters", device->fix->eph/100);
	}

	if (device && device->cell_info) {
		if (device->cell_info->flags & LOCATION_CELL_INFO_GSM_CELL_INFO_SET)
			g_debug("Mobile Country Code GSM: %d", device->cell_info->gsm_cell_info.mcc);

		if (device->cell_info->flags & LOCATION_CELL_INFO_WCDMA_CELL_INFO_SET)
			g_debug("Mobile Country Code WCDMA: %d", device->cell_info->wcdma_cell_info.mcc);
	}
  
	g_debug("Satellites in view: %d, in use: %d",
		device->satellites_in_view, device->satellites_in_use);
} 

Liblocation sends a "changed" signal also after locationing is started or stopped, in which case a last known fix is sent if such exists. Application can differentiate these fixes from real ones by inspecting device->status field which equals LOCATION_GPS_DEVICE_STATUS_NO_FIX if the fix is not real.

Starting and stopping locationing

Finally after everything above has been done, locationing can be started.

location_gpsd_control_start(control);

If the chosen location method violates control panel location settings, then a dialog is shown to user. Dialogs ask user to enable necessary services. On user's refusal an error to application is sent. If no error is seen, fixes should be coming after a while. When locationing is no longer needed, it can be stopped.

location_gpsd_control_stop(control);

Complete example

Here is a complete standalone example using liblocation. It starts location services after program is started, then when first fix arrives, prints it, stops services, and shutdowns.

#include <location/location-gps-device.h>
#include <location/location-gpsd-control.h>

static void on_error(LocationGPSDControl *control, gpointer data)
{ 
	g_debug("location error... quitting");
	g_main_loop_quit((GMainLoop *) data);
}

static void on_changed(LocationGPSDevice *device, gpointer data)
{
	if (!device)
		return;

	if (device->fix) {
		if (device->fix->fields & LOCATION_GPS_DEVICE_LATLONG_SET) {
			g_debug("lat = %f, long = %f", device->fix->latitude, device->fix->longitude);
			location_gpsd_control_stop((LocationGPSDControl *) data);
		}
	}
} 

static void on_stop(LocationGPSDControl *control, gpointer data)
{
	g_debug("quitting");
	g_main_loop_quit((GMainLoop *) data);
} 

static gboolean start_location(gpointer data)
{
	location_gpsd_control_start((LocationGPSDControl *) data);
	return FALSE;
}

int main(int argc, char *argv[])
{
	LocationGPSDControl *control;
	LocationGPSDevice *device;
	GMainLoop *loop;

	g_type_init();

	loop = g_main_loop_new(NULL, FALSE);

	control = location_gpsd_control_get_default();
	device = g_object_new(LOCATION_TYPE_GPS_DEVICE, NULL);

	g_object_set(G_OBJECT(control),
		"preferred-method", LOCATION_METHOD_USER_SELECTED,
		"preferred-interval", LOCATION_INTERVAL_DEFAULT,
		NULL);

	g_signal_connect(control, "error", G_CALLBACK(on_error), loop);
	g_signal_connect(device, "changed", G_CALLBACK(on_changed), control);
	g_signal_connect(control, "gpsd-stopped", G_CALLBACK(on_stop), loop);

	g_idle_add(start_location, control);

	g_main_loop_run(loop);

	g_object_unref(device);
	g_object_unref(control);

	return 0;
}

You can compile this example with following command:

gcc -Wall `pkg-config --cflags gl