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;

       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   comput-
       ers/devices, all of which he wishes to follow along together.

       Similarly, a group of people working closely together, such as transla-
       tors 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  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 as "new Speaker" events.  These beacons
       provide for receivers (Personal and Audience modes) to maintain a  man-
       aged  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 "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.

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  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 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.

   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  fre-
       quently,  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  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.  Overloaded  parame-
       ters 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  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 expected.  Brief experience during develop-
       ment 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  num-
       ber 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  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.

   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                             2018-04-27                      BIBLESYNC(7)
