changelog

最经典的bittorrent协议的实现的源码

                        Enhanced CTorrent Change Log
     _________________________________________________________________

   Changes for "dnh3.1" Release

   Features and Performance
     * Cached completed pieces are flushed to disk during idle time
       rather than immediately.
     * When the cache is full, a single entry is now flushed to make room
       for new data rather than flushing the entire cache.
     * Management of open files has been enabled in order to reduce the
       number of active file descriptors needed for large torrents.
       Detection and reporting of related errors is also improved.
     * Files are now opened in read-only mode when seeding.
     * The client will not connect to the tracker when quitting if it has
       not successfully made contact before.
     * A new command line option "-T" substitutes a hex representation of
       any non-printable characters in filenames; an underscore will be
       inserted between any such sequences and regular text. This applies
       to printing the name of the file as well as accessing it on disk,
       so you need to use it (or not) consistently across multiple runs
       of the same torrent. It does not apply to names specified with the
       -s option.
     * A new command line option "-X" specifies a "user exit" command to
       run upon download completion. The string parameter will be passed
       to the sh shell for execution; see the system() man page for
       further clarification. You will need to quote this string on the
       command line in order to identify it as a single parameter and
       prevent special characters from being interpreted. Some
       substitution sequences beginning with ampersand (&) are available;
       note that it's a good idea to quote the sequence within the string
       so that the substituted names will be quoted in the final command.
          + "&d" will be replaced by the name of the directory or
            filename that contains the downloaded data.
          + "&t" will be replaced by the name of the torrent metainfo
            file (with path, if it was specified that way to ctorrent).
          + "&w" will be replaced by the client's working directory.
       Note that the fork() and system() system/library functions are
       used for best portability. As a result, significant extra memory
       may be used while the specified command is running. Be advised to
       use this feature as a trigger mechanism to update a file or run a
       short script that kicks off a background task rather than for
       executing a longer task directly.
     * A new command line option "-d" specifies "daemon mode". The client
       will detach itself from the terminal session and become a
       background process. This option is also available from the
       operator menu.
     * Prefetch and total sent counts are reported with the cache stats
       in verbose mode. Note that these stats are all close
       approximations based on the default slice size of 16KB.
     * The -n option now accepts a list of files to download in priority
       order. Groups of simultaneous files can be specified, and
       "resuming normal behavior" after completion is now optional (and
       not the default). See the User's Guide for more detailed
       information.
     * The partial completion indicator ("P:") now shows percentages
       rather than number of pieces when using the new status line
       format. The download time remaining for the current set is also
       shown.
     * The CTCS protocol version has been incremented. Please download
       the new version of CTCS to take advantage of new features. This
       provides support for additional file details and prioritization,
       and for auto-configuration of available client configuration
       options in CTCS.
     * Output channels can now be changed via CTCS.
     * The input channel can now be redirected from the operator menu and
       CTCS.
     * Added "off" as an additional target for input and output channels.
     * Added support for systems that do not have snprintf() and/or
       vsnprintf().

   Bug Fixes
     * Fixed a missing maxfd variable initialization in the main loop,
       which could cause high CPU utilization. (maxfd patch)
     * Detect if the clock_gettime library function is missing and
       emulate it. This facilitates building on Mac OSX. (clock_gettime
       patch)
     * Avoid putting the "key" field into the tracker request twice.
     * Tracker redirection is now handled correctly and works.
     * Fixed problems with detection and reporting of tracker connection
       errors.
     * Error reading from disk with -c option is now reported.
     * Fixed a looping problem when the torrent begins with a zero-length
       file or a file of exactly one piece.
     * Fixed the way variable argument lists are handled in the console
       code, which could cause crashes. (console patch)
     * Fixed a problem flushing downloaded data to disk in certain
       situations. (flush patch)
     * Remove sockets from the list to check for peers disconnected
       during processing.
     * Updated fdset handling in peerlist, tracker, and ctcs components
       to set appropriate states in all cases.
     * Fixed a potential crash when receiving a message from a peer
       (after processing it). (msg patch)
     * Fixed an issue with rate measurement on NSLU2 devices. This was
       due to an apparent compiler bug (unconfirmed but raised to
       developers). There are other areas where the same effect can show
       itself (with the -E seed ratio option for instance) that cannot be
       so easily worked around. (bwrate patch)
     * Fixed an issue with null/redirected standard input.
     * If the time changes backward by a second, it is disregarded. This
       is not really a program bug fix, but a workaround for system clock
       glitches (observed on an NSLU2).

   Code Cleanup
     * Tracker request construction is somewhat consolidated and
       simplified.
     * Split the FillFDSet function into two functions of distinct roles
       and more manageable size.
     _________________________________________________________________

   Changes for "dnh3" Release

   Important Stuff to Know
     * You should always specify an upload bandwidth limit. With the most
       recent changes in the program, this "option" is not just a limit
       to stay under, but an advisement to the client as well. Enhanced
       CTorrent now tunes its upload performance based on the limit.
       Without a limit, the client has no idea how much bandwidth your
       line can support and so cannot perform this tuning. It is now
       possible to achieve better upload rates with a limit than without.
       Due to the tit-for-tat nature of bittorrent, this can also
       indirectly increase your download performance. If you just want
       the client to use as much upload bandwidth as possible, then
       choose a limit that is 10% or so less than the available upload
       capacity of your line. ("Available" means not typically in use by
       other applications.) Note that limits are specified in KB/s
       (kilobytes per second), where 1KB = 1024 bytes (8192 bits). Your
       ISP likely measures in "kilobits" (Kb, where 1Kb = 1000 bits or
       125 bytes) or "megabits" (1Mb = 1000000 bits or 122KB). Some of
       that [to the tune of 20% in some cases] is used by the line
       protocol and thus not available to you at all.
     * The CTCS protocol version has been incremented. If you've written
       an application that interfaces with CTorrent via the CTCS
       protocol, it should continue to work if you've used protocol level
       negotiation (PROTOCOL message). The new changes have been
       documented on the CTCS Protocol page.

   Features and Performance
     * Fast Restart
          + "Background" initial hash verification: Downloading and
            uploading will begin while pieces are being verified. Status
            will be updated as pieces are checked, and HAVE messages are
            sent as valid pieces are found.
          + A bitfield save file is always used. At startup, if a file of
            the same name as the torrent file with ".bf" appended is
            present, it is read to initialize the piece bitfield. The
            file is then deleted, and rewritten upon exit if downloading
            has not completed.
          + Pieces that are indicated as already present are verified by
            hash check (in the background). If the bitfield file is not
            found then all pieces are checked, unless this is the first
            time the torrent has been started.
          + The -b option can be used to specify a different bitfield
            filename. Difference: The option is generally not needed
            since it is now "on" by default. It now does not prevent hash
            checking when used.
          + The -f option now forces accuracy of the initial bitfield.
            Stated differently, it disables the initial hash checking of
            pieces on startup. This option should [still] be used with
            caution and is generally not recommended since background
            hash checking is now used. If the bitfield file is found at
            startup, it is used without verification; otherwise, seed
            mode is forced (without hash verification). Difference: The
            effect is generalized to apply to incomplete torrents (when a
            bitfield file is found) as well as the original behavior of
            forcing seed mode (without a bitfield file).
          + To emulate the original initial hash check behavior (avoiding
            background checking), use the -c and -f options together.
     * Cache Management
          + Automatic cache size: The -C option now specifies the maximum
            cache size, with the default remaining 16MB. The actual size
            used is determined by the download and upload rates and
            timings.
          + The maximum cache size that can be specified is no longer
            limited. The maximum size that will be used in any case is
            the size of the torrent.
          + Slices to be uploaded are prefetched into the cache during
            idle time. This can shave a few milliseconds off the time to
            respond to an upload request, and can also help performance
            during periods of heavy disk activity. The effectiveness may
            be reduced slightly when heavy upload limiting is used (as
            uploading patterns become less predictable), but it is also
            less critical then.
          + A more efficient cache aging mechanism has been added. This
            reduces CPU utilization and helps increase the accuracy of
            cache size management.
          + The cache is now indexed by piece to speed up searches and
            insertion.
          + Downloaded pieces are flushed to disk upon completion of each
            piece.
     * Unchoke Tuning
          + The number of unchoked peers will be increased automatically
            when the upload bandwidth limit is not being reached and
            decreased when there is much contention for upload bandwidth.
            This is done to maximize upload bandwidth utilization while
            also maximizing the upload rate to each unchoked peer.
          + Unchoke intervals are extended when necessary in order to
            insure that each unchoked peer has at least a chance of an
            opportunity to download.
          + You must specify an upload bandwidth limit in order to use
            these features. Without a limit, the client does not know the
            line capacity or available bandwidth. In that case TCP
            congestion control (the network protocol) limits the
            bandwidth, so the number of active upload streams (unchokes)
            is kept low in order to help it work properly when the line
            reaches its capacity.
     * Console I/O Management
       This is really a mostly-transparent enabler for other new current
       and future features.
          + Several configuration commands are available while running.
            Note that this requires termios, termio, or sgtty support to
            work properly; otherwise try pressing Enter after the key. It
            should be very rare for a system to not have one of these
            facilities.
               o Press "h" or "?" for a list of active keys. Inactive
                 keys will immediately update the status line.
               o Some commands prompt for additional input. The client
                 continues to run while waiting, though the status line
                 is not updated. An exception is the CTCS password; just
                 try to be relatively quick about it.
               o Commands shown with "+/-" use the "+" and "-" keys to
                 increment or decrement the value. After pressing the
                 command key, press "+" and/or "-" repeatedly to adjust
                 the value. After five presses, the increment is
                 increased; press the command key again if you wish to
                 reset it.
          + An Operator Menu allows changing output destinations,
            choosing an alternate status line format, and viewing
            detailed status information.
          + Presentation of messages between status line updates is
            cleaner.
          + A timestamp (raw clock value) is printed on "verbose" output.
     * Options
          + Added User-Agent header to the tracker request. A new option
            (-A) can be used to change the string that is sent (default
            is shown on the help screen). This feature should help with
            trackers that try to restrict use to recognized client
            programs. You should only need to use the -A option if the
            tracker has been set up to allow only specific clients
            (almost certainly out of admin ignorance in one way or
            another).
          + The -p option now specifies the highest port number to use.
            The client will count down from that point looking for an
            available port. This mimics the default behavior of counting
            down from port 2706.
          + A new command line option ("-a") can be used to preallocate
            the files to download. Use this if you are concerned about
            file fragmentation or out-of-order block storage. This option
            is only effective when initially creating the files and will
            cause startup to take longer as each entire file is written
            in order to reserve physical disk space. Note that all files
            will be created and preallocated even if the "-n" option is