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
biblesync.7
Description: Unix manual page
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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