Ubuntu Manpage: biblesync - multicast navigation synchronization in Bible programs

Provided by: libbiblesync-dev_2.1.0-2build1_amd64

NAME

       biblesync - multicast navigation synchronization in Bible programs

SYNOPSIS

       #include <biblesync.hh>

       typedef enum_BibleSync_mode {
           BSP_MODE_DISABLE,
           BSP_MODE_PERSONAL,
           BSP_MODE_SPEAKER,
           BSP_MODE_AUDIENCE,
           N_BSP_MODE
       } BibleSync_mode;

       typedef enum_BibleSync_xmit_status {
           BSP_XMIT_OK,
           BSP_XMIT_FAILED,
           BSP_XMIT_NO_SOCKET,
           BSP_XMIT_BAD_TYPE,
           BSP_XMIT_NO_AUDIENCE_XMIT,
           BSP_XMIT_RECEIVING,
           N_BSP_XMIT
       } BibleSync_xmit_status;

       typedef void (*BibleSync_navigate)(char cmd, string speakerkey,
                                          string bible, string ref, string alt,
                                          string group, string domain,
                                          string info,  string dump);

       Public interface:

       BibleSync *object = new BibleSync(string application,
                                         string version,
                                         string user);

       BibleSync_mode BibleSync::setMode(BibleSync_mode mode,
                                         BibleSync_navigate *nav_func,
                                         string passPhrase);
       BibleSync_mode BibleSync::getMode(void);
       string BibleSync::getVersion(void);
       string BibleSync::getPassphrase(void);
       BibleSync_xmit_status BibleSync::Transmit(string bible, string ref, string alt,
                                                 string group, string domain);
       BibleSync_xmit_status BibleSync::Chat(string message);
       static int BibleSync::Receive(void *object);
       bool BibleSync::setPrivate(bool privacy);
       void BibleSync::setBeaconCount(uint8_t count);
       void BibleSync::setUser(string user);
       void BibleSync::listenToSpeaker(bool listen, string speakerkey);

DESCRIPTION

       BibleSync  is  a  published  protocol  specification  by  which cooperating Bible programs
       navigate together.  It is implemented as a C++ class providing a  small,  clean  interface
       including  basic  setup,  take-down,  transmit,  polled  receive,  and  a bare few utility
       methods.

       The value of BibleSync is found in several examples:

       A single user may have multiple programs, or multiple computers/devices, all of  which  he
       wishes to follow along together.

       Similarly,  a  group  of  people  working closely together, such as translators or a group
       Bible study, can stay together as they work.

       In an instructional motif, BibleSync takes either the active or  passive  mode,  providing
       for a unidirectional navigation control.

BIBLESYNC ESSENTIALS

BibleSync communicates using local multicast. Three operational modes are provided:
Personal, Speaker, or Audience.

In Personal mode, BibleSync operates as a peer among peers, both sending and receiving
navigation synchronization on the shared local multicast network. Applications are
expected to respond appropriately to navigation, and to send synchronization events of
their own as the user moves about his Bible.

In Speaker or Audience mode, BibleSync either transmits only (Speaker) or receives only
(Audience) navigation. The Audience is expected to follow along with the Speaker's
direction. The Speaker ignores incoming navigation; the Audience transmits no navigation.

The difference between Personal and Speaker/Audience is thus strictly as to whether both
sides of the conversation are active for each participant.

On startup of the protocol, BibleSync transmits a presence announcement, informing other
communication partners of the application's participation. BibleSync makes this
announcement available to the application; whether the application shows these
announcements to the user is the application designer's choice.

Thereafter, as appropriate to the operational mode selected, BibleSync is tasked with
polled reception of incoming navigation event packets and transmission of navigation event
packets on the user's part.

Transmitters (Personal and Speaker modes) issue availability beacons every 10 seconds.
Received beacons for previously-unknown Speakers are handed up to the application as "new
Speaker" events. These beacons provide for receivers (Personal and Audience modes) to
maintain a managed list of available Speakers. Furthermore, when a transmitter ceases to
issue beacons, its presence in the list of available Speakers is aged out until being
removed after 30 seconds of beacon silence. The application is again informed as a
Speaker ages out with a "dead Speaker" event.

Default listening behavior is that the first Speaker heard via beacon is marked for
listening. Other transmitters claiming Speaker status via beacon are initially ignored,
but their presence is made known to the application. This provides for the application to
maintain a list from which the user can select Speakers he wishes to synchronize his
application. It is useful for the application to provide blanket "listen to all" and
"listen to none" functions, as well as per-Speaker selections, informing BibleSync of
these choices. In any case, this default "first Speaker only" policy can be overridden by
the application with any other policy desired, through the use of listenToSpeaker() as the
application designer requires.

Synchronization events include 5 data elements: The Bible abbreviation; the verse
reference; an alternate reference (if desired; not required) which may allow the
application to interpret better based on variant versification; a synchronization group
identifier; and the domain.

The group identifier is a single digit between 1 and 9. The specification is imprecise as
to this parameter's use. The initial implementation of BibleSync in Xiphos uses the
synchronization group as an indicator of the tab number in its tabbed interface: Not only
is the Bible navigated, but the tab in which to navigate is selected.

The domain parameter is currently fixed as "BIBLE-VERSE". This will be put to greater use
in future revisions of the protocol.

BibleSync transmits no packet when the application leaves the conversation.

PUBLIC INTERFACE

   Object creation
       The application must create a single BibleSync object, identifying the application's name,
       its version, and the user.

   setMode
       setMode  identifies  how BibleSync should behave. The application must provide as well the
       navigation callback function by which BibleSync will inform the  application  of  incoming
       events;  the  callback  makes  all  the  navigation  parameters  provided in event packets
       available to the application.   setMode  returns  the  resulting  mode.   The  application
       provides  the  passphrase to be used as well; this argument defaults to "" (empty string),
       indicating that the existing passphrase should be left in place.

   getMode
       The application may request the current mode.

   getVersion
       The version string of the library itself is returned.

   getPassphrase
       Intended for use when preparing to enter any active mode, the application may request  the
       current passphrase, so as to provide a default.

   Transmit
       The  protocol  requires  all  the indicated parameters, but all have defaults in Transmit:
       KJV, Gen.1.1, empty alternate, 1, and BIBLE-VERSE.

   Chat
       This is a  method  for  transmission  of  casual  text  messages  to  all  others  in  the
       conversation.   It  is  expected to be received by applications who will display them in a
       suitable manner to the user.

   Receive
       This is a static method accessible from either C or C++.   It  must  be  called  with  the
       object  pointer  so  as  to  re-enter  object  context  for the private internal receiver.
       Receive() must be called regularly (i.e. polled) as long as it continues to  return  TRUE.
       When  it  returns  FALSE,  it means that the mode has changed to BSP_MODE_DISABLE, and the
       scheduled polling should stop.  See also the note below on polled reception.

   setPrivate
       In the circumstance where the user has multiple programs running on a single computer  and
       does  not want his navigation broadcast outside that single system, when in Personal mode,
       the application may also request privacy.  The effect is to set  multicast  TTL  to  zero,
       meaning that packets will not go out on the wire.

   setBeaconCount
       Beacon  transmission  occurs  during every Nth call to Receive(); the default value is 10.
       This presumes the application will call Receive() once per second. If the application will
       call  Receive()  less frequently, divide that time (say, 2 seconds) into 10 to get a value
       (5) to use with this call. Use setBeaconCount() prior  to  enabling  Personal  or  Speaker
       mode.

   setUser
       If  the  application  allows  the  user  to  set  a name via settings dialog, setUser() is
       available to re-assign the associated user name as seen by others.

   listenToSpeaker
       Aside from default listen behavior detailed above, the application  specifically  asks  to
       listen  or  not  to  listen  to  specific  Speakers.   The  key  is as provided during the
       notification of a new Speaker.

RECEIVE USE CASES

There are 7 values for the cmd parameter of the nav_func. In all cases, the dump
parameter provides the raw content of an arriving packet.

'A'
Announce. A general presence message is in alt, and the individual elements are also
available, as overloaded use of the parameters: bible contains the user; ref contains the
IP address; group contains the application name and version; and domain contains the
device identification.

'N'
Navigation. The bible, ref, alt, group, and domain parameters are presented as they
arrived. info and dump are also available.

'S'
Speaker's initial recognition from beacon receipt. Overloaded parameters are available as
for presence announcements.

'D'
Dead Speaker. speakerkey holds the UUID key of a previously-identified application which
is no longer a candidate for listening.

'C'
Chat. Message text is in alt and other parameters are overloaded as per announce, above.

'M'
Mismatch. The incoming event packet is mismatched, either against the current passphrase
or for a navigation synchronization packet when BibleSync is in Speaker mode. The info
parameter begins with either "announce" or "sync", plus the user and IP address from whom
the packet came. As well, in the sync case, the regular bible, ref, alt, group, and
domain parameters are available. In the announce case, the presence message is in alt,
with overloaded individual parameters as previously described.

'E'
Error. This indicates network errors and malformed packets. The application's nav_func
is provided only the info and dump parameters.

NOTES

Polled reception
The application must provide a means by which to poll regularly for incoming packets. In
Xiphos, which is built on GTK and GLib, this is readily provided by mechanisms like
g_timeout_add(), which sets a regular interval call of the indicated function. GLib will
re-schedule the call as long as the called function returns TRUE. When it returns FALSE,
GLib un-schedules the call. Receive() adheres to this straightforward convention.
Therefore, it is imperative that every time the application moves from disabled to any
non-disabled mode, Receive is again scheduled for polled use.

A 1-second poll interval is expected. Brief experience during development has shown that
longer intervals lead to a perception of lag. If the application designer nonetheless
expects to call Receive() less frequently, it is necessary to use setBeaconCount() to
change the number of calls to it between beacon transmissions.

During every Receive() call, all waiting packets are processed.

No datalink security
BibleSync is a protocol defined for a friendly environment. It offers no security in its
current specification, and any packet sniffer such as wireshark(1) or tcpdump(8) can see
the entire conversation. The specification makes passing reference to future encryption,
but at this time none is implemented.

Managed Speaker lists
The addition of transmitter beacons was a result of initial experience showing that it can
be too easy for a user to mis-start BibleSync, or for a malicious user to interject
himself into serious work. The goal of beacons is to provide a means by which, on the one
hand, the user can be made aware of who is attempting to be a Speaker and, on the other
hand, confine the set of Speakers whom the user will permit to make synchronization
changes in the application. The simplest use of 'S' new Speaker notification events is to
respond with listenToSpeaker(true, speakerkey) which in effect makes BibleSync behave as
though there are no beacons. More serious use of 'S'/'D' is for the application to manage
its own sense of available Speakers, providing a means by which the user can make sensible
selections about how to react to each Speaker's presence. BibleSync can be told to listen
to legitimate Speakers, and to ignore interlopers, whether intended maliciously or merely
due to other users' inadvertent behavior.

Sending verse lists
One of the better uses of BibleSync is in sharing verse lists. Consider a relatively weak
application, perhaps on a mobile device, and a desktop-based application with strong
search capability. Run searches on the desktop, and send the result via BibleSync to the
mobile app. The ref parameter is not confined to a single reference. In normal citation
syntax, the verse reference may consist of semicolon-separated references, comma-separated
verses, and hyphen-separated ranges. Be aware that the specification has a relatively
short limit on packet size, so that at most a few dozen references will be sent.

Standard reference syntax
It is the responsibility of the application to transmit references in standard format.
BibleSync neither validates nor converts the application's incoming bible, ref, and alt
parameters. The specification references the BibleRef and OSIS specifications.