[sword-devel] BibleSync library -- any takers to integrate into your app?

Karl Kleinpaste karl at kleinpaste.org
Sun Jun 1 20:56:16 MST 2014


When I released Xiphos 3.2.0, I mentioned that it had a new feature,
BibleSync, to provide for multicast co-navigation of Bible programs. 
I've now separated BibleSync into a distinct library outside Xiphos,
able to be built and linked separately.

I would be interested to hear from any of the other Sword apps' authors
who would be interested in experimenting with integrating BibleSync
capability.

Short summary: BibleSync is a single C++ class library that provides a
minimal public interface with the essentials needed to configure,
transmit, and receive through the metaphorical conduit through which
navigation packets travel.  The requirements to use it well are
straightforward, involving mode selection, polled call of the receiver,
calling the transmitter as needed, and identifying which other potential
transmitters should be heard according to user request and with regard
to default listen policy.  Options exist to specify total privacy if
only the current system's apps should hear nav transmit, and whether the
overall operational mode should be pure Speaker, pure Audience, or mixed
Personal mode which both transmits and receives among cooperating apps
(e.g. small team).

BibleSync has a github repository you can clone:
https://github.com/karlkleinpaste/biblesync.git

If you care to see it operate in Xiphos, you can build both BibleSync
and Xiphos, or if you use Windows or Wine, you can just try out the
3.2.1pre Win32 installer found in
http://ftp.xiphos.org/sword/biblesync/1.0.1/.  (It's visually poor under
Wine but fully functional.)  See the screenshots in the same directory
for the Prefs page showing BibleSync configuration.  Obviously you'll
have to run multiple instances; I've run as many as 9 simultaneously, on
an assortment of real hardware and VMs.  The manual needs an update.

I've attached the man page in both regular format and post-processed
text format.

Be aware that the current implementation takes a few liberties with the
original spec (compare .hh against spec, mentioned in man page) that are
well-received so far by the group of people working on this, plus the
addition of transmitter beacons which is waiting for critique and
consensus.  Beacons, or something similar, were deemed necessary to deal
with the problem of interloper transmitters, whether maliciously or
inadvertently.  Note that BibleSync in Xiphos 3.2.0 and 3.2.1pre will
not interoperate because of the new beacon aspect: 3.2.0 will not
understand or generate them and 3.2.1 will not recognize Speakers
without them.

It's new, it's weird, it's cool, it's exactly the kind of thing people
like us should find interesting. :-)

--karl
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BIBLESYNC(7)               Linux Programmer's Manual              BIBLESYNC(7)



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;

       #define BSP_ANNOUNCE   1
       #define BSP_SYNC       2
       #define BSP_BEACON     3

       typedef void (*BibleSync_navigate)(char cmd,
                                          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(char type,
                                         string bible, string ref, string alt,
                                         string group, string domain);
       static int BibleSync::Receive(void *object);
       bool BibleSync::setPrivate(bool privacy);
       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   comput-
       ers/devices, all of which he wishes to follow along together.

       Similarly, a group of people working closely together, such as transla-
       tors, 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  send-
       ing and receiving navigation synchronization on the shared local multi-
       cast 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  incom-
       ing 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  par-
       ticipant.

       On  startup  of  the protocol, BibleSync transmits a presence announce-
       ment, informing other communication partners of the application's  par-
       ticipation.   BibleSync makes this announcement available to the appli-
       cation; 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.   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 when a Speaker goes dead.

       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 "lis-
       ten 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  applica-
       tion  with  any  other  policy  desired,  through the use of listenToS-
       peaker() 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 specifica-
       tion is imprecise as to this parameter's use.  The initial  implementa-
       tion  of BibleSync in Xiphos uses the synchronization group as an indi-
       cator 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 conversa-
       tion.

       Only  the  3  packet  types  BSP_ANNOUNCE, BSP_SYNC, and BSP_BEACON are
       defined in the protocol.

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 pro-
       vides 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  applica-
       tion may request the current passphrase, so as to provide a default.

   Transmit
       The application must provide the message type, which in the normal case
       should be BSP_SYNC.  The protocol requires all  the  indicated  parame-
       ters, but all have defaults in Transmit: KJV, Gen.1.1, empty alternate,
       1, and BIBLE-VERSE.

   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  sched-
       uled 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.

   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  6  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  identifi-
       cation.

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

   'S'
       Speaker's initial recognition from beacon receipt.  alt  holds  a  UUID
       key  identifying the particular application.  Overloaded parameters are
       available as for presence announcements.

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

   '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  pres-
       ence message is in alt, with overloaded individual parameters as previ-
       ously 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 regu-
       lar 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 straight-
       forward  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  suggested.   Brief  experience  during
       development has shown that longer intervals lead  to  a  perception  of
       lag.

       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  listenToS-
       peaker(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 legiti-
       mate Speakers, and to ignore interlopers, whether intended  maliciously
       or merely due to other users' inadvertent behavior.

   Protocol extensions
       This implementation takes certain liberties with the specification.  In
       light of this being the first functioning, published implementation  of
       BibleSync,  these changes are intended to be reflected in a near-future
       specification update.

   Conformity checks
       This implementation does not guarantee conformity of  incoming  packets
       in 2 areas:

       The  names in the "name=value" pairs are expected to be composed from a
       particular character subset.  This implementation does not verify this.
       At this time, any non-NUL characters left of '=' are acceptable.

       Continuation  lines in "name=value" pairs are defined by the specifica-
       tion, but this implementation does not support them.

   Sending verse lists
       One of the better uses of BibleSync is in sharing  verse  lists.   Con-
       sider  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 applica-
       tion's incoming bible, ref, and alt parameters.  The specification ref-
       erences the BibleRef and OSIS specifications.

SEE ALSO
       http://biblesyncprotocol.wikispaces.com  (user  "General_Public", pass-
       word "password"), http://semanticbible.com/bibleref/bibleref-specifica-
       tion.html, socket(2), setsockopt(2), select(2), recvfrom(2), sendto(2),
       and ip(7), especially sections on  IP_ADD_MEMBERSHIP,  IP_MULTICAST_IF,
       IP_MULTICAST_LOOP, and IP_MULTICAST_TTL.



Linux                             2014-06-01                      BIBLESYNC(7)


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