## EpcDispatcher

EpcDispatcher — publish DNS-SD services

## Stability Level

Unstable, unless otherwise indicated

## Synopsis

    #include <libepc/dispatcher.h>

    enum                EpcAddressFamily;
    enum                EpcCollisionHandling;
                        EpcDispatcherPrivate;
    struct              EpcDispatcherClass;
    struct              EpcDispatcher;
    EpcDispatcher *     epc_dispatcher_new                  (const gchar *name);
    gboolean            epc_dispatcher_run                  (EpcDispatcher *dispatcher,
                                                             GError **error);
    void                epc_dispatcher_reset                (EpcDispatcher *dispatcher);
    void                epc_dispatcher_add_service          (EpcDispatcher *dispatcher,
                                                             EpcAddressFamily protocol,
                                                             const gchar *type,
                                                             const gchar *domain,
                                                             const gchar *host,
                                                             guint16 port,
                                                             ...);
    void                epc_dispatcher_add_service_subtype  (EpcDispatcher *dispatcher,
                                                             const gchar *type,
                                                             const gchar *subtype);

    void                epc_dispatcher_set_collision_handling
                                                            (EpcDispatcher *dispatcher,
                                                             EpcCollisionHandling method);
    void                epc_dispatcher_set_cookie           (EpcDispatcher *dispatcher,
                                                             const gchar *cookie);
    void                epc_dispatcher_set_name             (EpcDispatcher *dispatcher,
                                                             const gchar *name);
    void                epc_dispatcher_set_service_details  (EpcDispatcher *dispatcher,
                                                             const gchar *type,
                                                             ...);

    EpcCollisionHandling epc_dispatcher_get_collision_handling
                                                            (EpcDispatcher *dispatcher);
    const gchar *       epc_dispatcher_get_cookie           (EpcDispatcher *dispatcher);
    const gchar *       epc_dispatcher_get_name             (EpcDispatcher *dispatcher);

    GEnumClass *        epc_address_family_get_class        (void);
    const gchar *       epc_address_family_to_string        (EpcAddressFamily value);
    GEnumClass *        epc_collision_handling_get_class    (void);
    const gchar *       epc_collision_handling_to_string    (EpcCollisionHandling value);

## Object Hierarchy

      GEnum
       +----EpcAddressFamily

      GEnum
       +----EpcCollisionHandling

      GObject
       +----EpcDispatcher

## Properties

      "collision-handling"       EpcCollisionHandling  : Read / Write / Construct
      "cookie"                   gchar*                : Read / Write / Construct
      "name"                     gchar*                : Read / Write / Construct

## Description

The EpcDispatcher object provides an easy method for publishing DNS-SD services. Unlike established APIs like Avahi or HOWL the EpcDispatcher doesn't expose any state changes reported by the DNS-SD daemon, but instead tries to handle them automatically. Such state changes include, for instance, name collisions or a restart of the DNS-SD daemon.

Example 7. Publish a printing service

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    dispatcher = epc_dispatcher_new ("Dead Tree Desecrator");

    epc_dispatcher_add_service (dispatcher, EPC_ADDRESS_IPV4, "_ipp._tcp",
                                NULL, NULL, 651, "path=/printers", NULL);
    epc_dispatcher_add_service (dispatcher, EPC_ADDRESS_UNSPEC,
                                "_duplex._sub._printer._tcp",
                                NULL, NULL, 515, NULL);

## Details

### enum EpcAddressFamily

    typedef enum {
      EPC_ADDRESS_UNSPEC = AF_UNSPEC,
      EPC_ADDRESS_IPV4 = AF_INET,
      EPC_ADDRESS_IPV6 = AF_INET6
    } EpcAddressFamily;

The address family to use for contacting network services.

`EPC_ADDRESS_UNSPEC` | No preferences exist. Use all address families supported.
`EPC_ADDRESS_IPV4` | Exclusively use IPv4 for addressing network services.
`EPC_ADDRESS_IPV6` | Exclusively use IPv6 for addressing network services.

### enum EpcCollisionHandling

    typedef enum {
      EPC_COLLISIONS_IGNORE,
      EPC_COLLISIONS_CHANGE_NAME,
      EPC_COLLISIONS_UNIQUE_SERVICE
    } EpcCollisionHandling;

Various strategies for handling service name collisions.

`EPC_COLLISIONS_IGNORE` | Don't handle collisions at all, just fail silently.
`EPC_COLLISIONS_CHANGE_NAME` | Try to announce the service with another name.
`EPC_COLLISIONS_UNIQUE_SERVICE` | Defer own service announcement until the other service. disappears.

### EpcDispatcherPrivate

    typedef struct _EpcDispatcherPrivate EpcDispatcherPrivate;

Private fields of the EpcDispatcher class.

### struct EpcDispatcherClass

    struct EpcDispatcherClass {
    };

Virtual methods of the EpcDispatcher class.

### struct EpcDispatcher

    struct EpcDispatcher;

Public fields of the EpcDispatcher class.

### epc_dispatcher_new ()

    EpcDispatcher *     epc_dispatcher_new                  (const gchar *name);

Creates a new EpcDispatcher object for announcing a DNS-SD service. The service is announced on all network interfaces.

Call `epc_dispatcher_add_service()` to actually announce a service.

`name` : | the human friendly name of the service
Returns : | the newly created EpcDispatcher object.

### epc_dispatcher_run ()

    gboolean            epc_dispatcher_run                  (EpcDispatcher *dispatcher,
                                                             GError **error);

Starts the Avahi client of the EpcDispatcher. If the client was not started, the function returns `FALSE` and sets `error`. The error domain is EPC_AVAHI_ERROR. Possible error codes are those of the Avahi library.

`dispatcher` : | a EpcDispatcher
`error` : | return location for a GError, or `NULL`
Returns : | `TRUE` when the dispatcher was started successfully, `FALSE` if an error occurred.

### epc_dispatcher_reset ()

    void                epc_dispatcher_reset                (EpcDispatcher *dispatcher);

Revokes all service announcements of this EpcDispatcher.

`dispatcher` : | a EpcDispatcher

### epc_dispatcher_add_service ()

    void                epc_dispatcher_add_service          (EpcDispatcher *dispatcher,
                                                             EpcAddressFamily protocol,
                                                             const gchar *type,
                                                             const gchar *domain,
                                                             const gchar *host,
                                                             guint16 port,
                                                             ...);

Announces a TCP/IP service via DNS-SD.

The service `type` shall be a well-known DNS-SD service type as listed on http://www.dns-sd.org/ServiceTypes.html. This function tries to announce both the base service type and the sub service type when the service name contains more than just one dot: Passing "_anon._sub._ftp._tcp" for @type will announce the services "_ftp._tcp" and "_anon._sub._ftp._tcp".

The function can be called more than once. Is this necessary when the server provides different access methods. For instance a web server could provide HTTP and encrypted HTTPS services at the same time. Calling this function multiple times also is useful for servers providing the same service at different, but not all network interfaces of the host.

When passing %NULL for @domain, the service is announced within the local network only, otherwise it is announced at the specified DNS domain. The responsible server must be configured to support DNS-SD.

Pass `NULL` for `host` to use the official host name of the machine to announce the service. On machines with multiple DNS entries you might want to explictly choose a fully qualified DNS name to announce the service.

`dispatcher` : | a EpcDispatcher
`protocol` : | the EpcAddressFamily this service supports
`type` : | the machine friendly name of the service
`domain` : | the DNS domain for the announcement, or `NULL`
`host` : | the fully qualified host name of the service, or `NULL`
`port` : | the TCP/IP port of the service
`...` : | an optional list of TXT records, terminated by `NULL`

### epc_dispatcher_add_service_subtype ()

    void                epc_dispatcher_add_service_subtype  (EpcDispatcher *dispatcher,
                                                             const gchar *type,
                                                             const gchar *subtype);

Announces an additional sub service for a registered DNS-SD service.

### Note

This function will fail silently, when the service specified by `type` hasn't been registered yet.

`dispatcher` : | a EpcDispatcher
`type` : | the base service type
`subtype` : | the sub service type

### epc_dispatcher_set_collision_handling ()

    void                epc_dispatcher_set_collision_handling
                                                            (EpcDispatcher *dispatcher,
                                                             EpcCollisionHandling method);

Changes the collision handling strategy the dispatcher uses. See "collision-handling" for details.

`dispatcher` : | a EpcDispatcher
`method` : | the new strategy

Since 0.3.1

### epc_dispatcher_set_cookie ()

    void                epc_dispatcher_set_cookie           (EpcDispatcher *dispatcher,
                                                             const gchar *cookie);

Changes the unique identifier of the service. See "cookie" for details.

`dispatcher` : | a EpcDispatcher
`cookie` : | the new service identifier, or `NULL`

Since 0.3.1

### epc_dispatcher_set_name ()

    void                epc_dispatcher_set_name             (EpcDispatcher *dispatcher,
                                                             const gchar *name);

Changes the user friendly name used for announcing services. See "name".

`dispatcher` : | a EpcDispatcher
`name` : | the new user friendly name

### epc_dispatcher_set_service_details ()

    void                epc_dispatcher_set_service_details  (EpcDispatcher *dispatcher,
                                                             const gchar *type,
                                                             ...);

Updates the list of TXT records for a registered DNS-SD service. The TXT records are specified by the service type and usually have the form of key-value pairs:

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    path=/dwarf-blog/

### Note

This function will fail silently, when the service specified by `type` hasn't been registered yet.

`dispatcher` : | a EpcDispatcher
`type` : | the service type
`...` : | a list of TXT records, terminated by `NULL`

### epc_dispatcher_get_collision_handling ()

    EpcCollisionHandling epc_dispatcher_get_collision_handling
                                                            (EpcDispatcher *dispatcher);

Queries the collision handling strategy the dispatcher uses. See "collision-handling" for details.

`dispatcher` : | a EpcDispatcher
Returns : | The dispatcher's collision handling strategy, or EPC_COLLISIONS_IGNORE on error.

Since 0.3.1

### epc_dispatcher_get_cookie ()

    const gchar *       epc_dispatcher_get_cookie           (EpcDispatcher *dispatcher);

Queries the unique identifier of the service. See "cookie" for details.

`dispatcher` : | a EpcDispatcher
Returns : | The unique identifier of the service, or `NULL` on error.

Since 0.3.1

### epc_dispatcher_get_name ()

    const gchar *       epc_dispatcher_get_name             (EpcDispatcher *dispatcher);

Queries the user friendly name used for announcing services. See "name".

`dispatcher` : | a EpcDispatcher
Returns : | The user friendly name of the service.

### epc_address_family_get_class ()

    GEnumClass *        epc_address_family_get_class        (void);

Retrieves the GEnumClass describing the EpcAddressFamily enum.

Returns : | The GEnumClass describing EpcAddressFamily.

### epc_address_family_to_string ()

    const gchar *       epc_address_family_to_string        (EpcAddressFamily value);

Retrieves the name of a EpcAddressFamily `value`, or `NULL` when `value` is invalid.

`value` : | a EpcAddressFamily value
Returns : | The string representation of `value`, or `NULL`.

### epc_collision_handling_get_class ()

    GEnumClass *        epc_collision_handling_get_class    (void);

Retrieves the GEnumClass describing the EpcCollisionHandling enum.

Returns : | The GEnumClass describing EpcCollisionHandling.

### epc_collision_handling_to_string ()

    const gchar *       epc_collision_handling_to_string    (EpcCollisionHandling value);

Retrieves the name of a EpcCollisionHandling `value`, or `NULL` when `value` is invalid.

`value` : | a EpcCollisionHandling value
Returns : | The string representation of `value`, or `NULL`.

## Property Details

### The `"collision-handling"` property

      "collision-handling"       EpcCollisionHandling  : Read / Write / Construct

The collision handling method to use.

Default value: EPC_COLLISIONS_CHANGE_NAME

### The `"cookie"` property

      "cookie"                   gchar*                : Read / Write / Construct

Unique identifier of the service.

Default value: NULL

### The `"name"` property

      "name"                     gchar*                : Read / Write / Construct

User friendly name of the service.

Default value: NULL