Enhanced CTorrent User's Guide

   This guide is presented to offer additional information related to
   using [1]Enhanced CTorrent.

   This document is not an introduction to BitTorrent--for that, try
   [2]this, [3]this, or an Internet search.

  Contents

     * Options
          + [4]General
          + [5]Downloading
          + [6]Create Torrent
     * [7]Examples
     * [8]Runtime Commands
          + [9]Operator Menu
     * Usage Notes
          + [10]Bandwidth Limits
          + [11]Startup
          + [12]Status Line
          + [13]Stopping CTorrent

   Options Index
   [14]-a [15]-A [16]-b [17]-c [18]-c [19]-C [20]-d [21]-D [22]-e [23]-E
   [24]-f [25]-i [26]-I [27]-l [28]-m [29]-M [30]-n [31]-p [32]-p [33]-P
   [34]-s [35]-s [36]-S [37]-t [38]-T [39]-u [40]-u [41]-U [42]-v [43]-x
   [44]-X [45]-z
     _________________________________________________________________

   Options
   ___________________________________

  General Options


-x          Decode metainfo (torrent) file only, don't download

          Displays the torrent information and contents from the metainfo
          (.torrent) file. No piece checking or downloading is performed.
          This option is normally used alone.


-c          Check pieces only, don't download

          Hash-checks all pieces of the torrent to verify completion
          status and exits. Use this when you want to verify that you've
          successfully downloaded the complete torrent, or to make sure
          the files are intact after a system crash. This option is
          normally used alone, but can be used with -X for an automated
          completion check.


-v          Verbose output (for debugging)

          Generates [a lot of] extra output while CTorrrent is running.
   ___________________________________

  Downloading Options


-e int      Exit while seed <int> hours later (default 72 hours)

          Indicate how long (in hours) you want to "seed" (continue
          uploading) after download has completed. It is considered
          polite and fair (and required by some tracker sites) to seed
          for some time after downloading.


-E num      Exit after seeding to <num> ratio (UL:DL)

          Specify a desired "seed ratio". After downloading completes,
          the client will continue seeding (uploading) until your total
          upload volume divided by your download volume equals this
          number. Fractional values (such as 1.5) are allowed. It is
          considered polite and fair (and required by some tracker sites)
          to seed until your ratio is at least 1:1.


-i ip       Listen for connections on specific IP address (default all/any)

          Specify the IP address on which you want to listen for incoming
          connections. This is only useful if your system has multiple
          network interfaces and you want to restrict access or run
          multiple clients on different interfaces.


-p port     Listen port (default 2706 -> 2106)

          Specify the TCP port number on which to listen for incoming
          connections. By default, CTorrent starts at 2706 and searches
          for an available port in decreasing order until it finds one or
          exhausts all ports down through 2106. The behavior with this
          option is similar, but starting at the specified port number.


-I ip       Specify public/external IP address for peer connections

          Specify the IP address which the tracker should give out to
          peer clients in order to connect to you. This is normally
          needed only if you are behind a NAT and on the tracker's local
          network.


-u num or URL   Alternate announce (tracker) URL

          Specify an alternate tracker announce URL. The parameter can be
          the actual URL or the number from the list of alternates
          printed when starting the client or using -x.


-s filename     Download ("save as") to a different file or directory

          Download to a different filename or top-level directory name
          than what is given in the metainfo file.


-C cache_size   Cache size, unit MB (default 16MB)

          Specify the maximum amount of memory to use for caching
          downloaded slices. The program may use less than this; the
          cache size is dynamically tuned based on the download and
          upload rates. You may need to use this option if running on a
          memory-constrained system such as a router or SAN device. If
          you use a value of 0, no memory cache will be used but the
          process will be more disk-intensive.


-f              Force saved bitfield or seed mode (skip hash check at startup)

          Perform a fast startup by skipping the initial (or background)
          hash verification of the files. This option is not generally
          recommended since the client now performs initial hash checking
          in the background. Use this option only if CTorrent was shut
          down cleanly when last downloading this torrent and you are
          absolutely certain that the bitfield (if download is not
          complete) and data files are intact and correct. To emulate the
          old behavior of hash-checking all pieces before beginning
          download or seeding, use -f along with the -c option.


-b filename     Specify bitfield save file (default is torrent+".bf")

          Piece completion status is saved to a bitfield file on exit if
          download has not completed. On startup the file is read to
          determine (and check) available pieces. The -b option can be
          used to specify a filename other than the default. Be
          consistent and careful with this option; it is generally not
          needed.


-M max_peers    Max peers count (default 100)

          Set the maximum allowable number of peer connections. If this
          number is reached, no new connections will be initiated or
          accepted. If memory or upload bandwidth are constrained, you
          may want to use this option to specify a lower value.


-m min_peers    Min peers count (default 1)

          Set the desired minimum number of peer connections. If the
          number falls below this value, the client will contact the
          tracker to request more peers.


-z slice_size   Download slice/block size, unit KB (default 16, max 128)

          Sets the size of the basic unit of download. For greatest
          compatibility with other peer clients, use the default. This
          value can also affect the precision with which bandwidth is
          managed.


-n file_list    Specify file number(s) to download

          Specify a priority order for downloading files in the torrent.
          A comma-separated list of file numbers and groups can be
          specified; the file numbers can be seen with the -x option. The
          client will preferentially request pieces of the
          highest-priority files, requesting a piece from a
          lower-priority group if a peer has no such pieces.
          A group may consist of:

          + a file number
          + a range of file numbers (x-y)
          + a combination of file numbers and ranges separated with plus
            (+) signs
          + an asterisk (*) or 3-dot ellipsis (...)

          If an asterisk (remember to quote it on the command line!) or
          ellipsis is used, the client will download and seed the
          remainder of the torrent once the prioritized files are
          completed; this is similar to the previous behavior of the
          option. If no such specification is given, the client will
          download and seed only the indicated files.
          Examples:

        -n 3
                Download and seed only file 3.

        -n 3+5+7,8-11
                Download files 3, 5, and 7 simultaneously, then download
                files 8 through 11 simultaneously, then stop downloading
                and seed all downloaded files.

        -n 3-4,...
                Download files 3 and 4 simultaneously, then download and
                seed all remaining content.


-D rate         Max bandwidth down (unit KB/s)

          Specify a download bandwidth limit for this torrent. The client
          will maintain its short-term average download rate at or below
          this value.


-U rate         Max bandwidth up (unit KB/s)

          Specify an upload bandwidth limit for this torrent. The client
          will maintain its short-term average upload rate at or below
          this value.


-P peer_id      Set Peer ID prefix. (default "-CD0301-")

          Specify an alternate peer ID prefix. This can be useful if a
          tracker is set up to only allow client programs that it
          recognizes. (The admin may not even realize it, so you may want
          to try contacting them to request that they change their
          configuration or add Enhanced CTorrent to the list.) If you
          receive a tracker warning message that your client is out of
          date, try using this option with the prefix of another
          well-known client program (such as "-AZ2304-").


-A user_agent   Set User-Agent header. (default "Enhanced-CTorrent/dnh3.1")

          Specify an alternate user-agent header. This can be useful if a
          tracker is set up to only allow client programs that it
          recognizes.


-S host:port    Use CTCS server at host:port

          Maintain a connection to CTCS for status reporting, bandwidth
          control, and client management. Using a colon at the end of the
          parameter (as in "-S localhost:2780:") will cause the client to
          prompt for a password to send to CTCS when connecting.


-a              Preallocate files on disk

          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 used to download a
          particular file.


-T              Convert foreign filenames to printable text

          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.


-X command      Run command upon download completion ("user exit")

          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.
          This option can also be used together with -c as an automated
          completion check. Normally the completion command will be run
          only if data has been downloaded; this case is the exception.


-d              Daemon mode (fork to background)

          The client will detach itself from the terminal session and
          become a background process, closing stdin, stdout, and stderr.
          There is no way to bring it back into the foreground of a
          session later; if you want to monitor or manage the client then
          either use the CTCS option (-S) as well or run the client under
          [46]screen instead of using -d.
          If this option is specified twice (-dd) then redirected
          standard I/O descriptors will not be closed.
   ___________________________________

  Options for Creating a New Torrent


-t              Create a new torrent file

          Indicates that you want to create a new torrent. This must be
          the first option specified when creating a torrent.


-s filename     Specify metainfo file name

          (Required) Give the name of the file to be created.


-u URL          Tracker's URL

          (Required) Specify the tracker's announce URL. This usually
          looks similar to "http://tracker.example.com:port/announce".


-l piece_len    Piece length (default 262144)

          Specify the piece size for your torrent. This will also
          determine the number of pieces in the torrent.


-p              Private (disable peer exchange)

          Disable the use of DHT, PEX, or other trackerless peer-exchange
          methods by other clients when sharing this torrent.


-c comment      Include a comment/description

          Include a comment field in the torrent file.
     _________________________________________________________________

   Examples

   List the contents of a torrent:

ctorrent -x example.torrent

   Verify download completion status (takes a little time):

ctorrent -c example.torrent

   Download or seed a torrent using default options:

ctorrent example.torrent

   Download with a limit of 100KB/s, upload limit of 10KB/s, and seed
          until a ratio of 1.5:1 is achieved:

ctorrent -D 100 -U 10 -E 1.5 example.torrent

   Create a torrent:

ctorrent -t -u "http://tracker.example.com:6969/announce" -s example.torrent fi
le_or_dir_to_upload
     _________________________________________________________________

   Runtime Commands

   Several commands are available during upload/download; a list is
   available by pressing ? or h:
Available commands:
 [Esc/0]  Operator menu                  m[+/-]   Adjust min peers count
 d[+/-]   Adjust download limit          M[+/-]   Adjust max peers count
 u[+/-]   Adjust upload limit            C[+/-]   Adjust max cache size
 n        Download specific file         S        Set/change CTCS server
 e[+/-]   Adjust seed exit time          v        Toggle verbose mode
 E[+/-]   Adjust seed exit ratio         Q        Quit
 X        Completion command

   Command keys are case-sensitive. When a command key is pressed, a
   prompt or current value is displayed. Prompts will suspend display of
   the status line while waiting for input, though the client continues
   to run normally. Toggle and numeric commands briefly suspend the
   status line display.

   Commands shown with [+/-] following the key are numeric options and
   can be adjusted by pressing + or - repeatedly after the command key.
   The increment is increased after five presses; to reset it, press the
   command key again.

   Most commands use the same letter as the corresponding command-line
   option. Note that the bandwidth limit commands use the same letters
   but opposite case.

  Operator Menu

   The 0 or Esc command key displays an operator menu with more advanced
   (or less routine) options. All options on and beneath this menu
   require pressing Enter to submit the input. Pressing Enter alone will
   exit the menu.
Operator Menu
 Output Channels:
  1) Normal/status:  stdout
  2) Interactive:    stdout
  3) Error/warning:  stderr
  4) Debug/verbose:  stderr
  5) Input:          stdin
 Status Line Formats:
  6) \ 0/6/18 [700/700/700] 0MB,11127MB | 0,15K/s | 0,0K E:0,405
 *7) | S:0/10 L:6/7 C:0  R=15.92 D=0 U=16 K/s  seeding 48:57
 Other options:
  8) View detailed status
  9) Pause (suspend upload/download)
 10) Become daemon (fork to background)
 11) Update tracker stats & get peers
 12) Restart (recover) the tracker session
Enter selection:

   The first set of options allow redirection of the client's various
   types of console output (or even input--use carefully!). Of particular
   use is the debug/verbose channel, which can be directed to a file to
   create a debug log (be sure to also enable verbose output with the "v"
   command key or CTCS).

   The second set of options is used to select the status line format.
   Since the actual client status is used to generate the menu options,
   the operator menu display can also be used just to view the alternate
   status information. An asterisk (*) indicates the currently selected
   format.

   The next two options provide a means to view more detailed current
   status and statistics or to pause uploading and downloading (more or
   less immediately, unlike the previous CTCS pause function).

   Note that there is no "recovery" from daemon mode. Use CTCS (with
   daemon mode) and/or "screen" if you want the client to run in the
   background but need to manage or monitor it.

   The next two options are the same as the corresponding actions in
   CTCS. The first performs an early tracker update. The second restarts
   the tracker session as if you had exited and restarted the client.
   This can be used to recover if the tracker appears to have suffered a
   failure and does not recognize your client session.
     _________________________________________________________________

   Usage Notes

  Bandwidth Limits

   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.

  Startup

   If you have previously started the torrent, CTorrent will perform a
   hash-check of all pieces (or pieces indicated by the bitfield file if
   present) while beginning the upload/download process. This does not
   mean that it is starting over--quite the opposite! This is how the
   client determines which pieces it already has so that they will not be
   downloaded again (and can be offered for uploading). This process
   confirms the pieces that you have even if the files have been altered
   or recovered after a system crash.

  Status Line

   The status line that is output by the client has changed since the
   original and deserves some explanation.

    / 0/33/110 [672/672/672] 0MB,1130MB | 0,20K/s | 0,0K E:0,31 P:4/10
    - - -- ---  --- --- ---  --- ------   - --      - -    - --   ----
    A B  C  D    E   F   G    H     I     J  K      L M    N  O     P

   A: Ticker; this character changes to indicate that the client is
   running.
   B: Number of seeders (complete peers) to which you are connected.
   C: Number of leechers (incomplete peers) to which you are connected.
   D: Total number of peers in the swarm, as last reported by the
   tracker.
   E: Number of pieces of the torrent that you have completed.
   F: Total number of pieces in the torrent.
   G: Number of pieces currently available from you and your connected
   peers.
   H: Total amount of data you have downloaded.
   I: Total amount of data you have uploaded.
   J: Your current download rate (20 second average).
   K: Your current upload rate (20 second average).
   L: Amount of data downloaded since the last status line update.
   M: Amount of data uploaded since the last status line update.
   N: Number of tracker connection errors.
   O: Number of successful tracker connections.
   P: Completion ratio of current fileset (when -n is used).

   Additional information such as tracker connection status may be
   displayed at the end of the status line when appropriate.

  Alternate Status Line

   A new status line format is also available via the operator menu.

    / S:4/8 L:4/5 C:1  R=5.85 D=42 U=16 K/s  79/100% 49:47  P:40/100% 2:41
    -   - -   - -   -    ----   --   --      -- ---- -----    ------- ----
    A   B C   D E   F      G     H    I       J   K    L         M      N

   A: Ticker; this character changes to indicate that the client is
   running.
   B: Number of seeders (complete peers) to which you are connected.
   C: Number of seeders in the swarm (excluding yourself), as last
   reported by the tracker.
   D: Number of leechers (incomplete peers) to which you are connected.
   E: Number of leechers in the swarm (excluding yourself), as last
   reported by the tracker.
   F: Number of peer connection attempts in progress.
   G: Your upload/download ratio.
   H: Your current download rate (20 second average).
   I: Your current upload rate (20 second average).
   J: Percent of the torrent that you have completed.
   K: Percent of the torrent currently available from you and your
   connected peers.
       If you have the complete torrent, "seeding" is displayed instead
   of these percentages.
   L: Estimated download or seed time remaining, in hours and minutes.
   M: Completion and availability of current fileset (when -n is used).
   N: Time remaining to complete the current fileset (when -n is used).

   Additional information such as tracker connection status may be
   displayed at the end of the status line when appropriate.

  Stopping CTorrent

   Besides the Q command key (equivalent to Ctrl-C but a nicer user
   interface), CTorrent can be stopped before completing download or
   seeding by pressing Ctrl-C or sending the TERM signal ("kill pid").
   This will tell the client to contact the tracker to send its final
   statistics and advise that it is leaving the torrent. Note that this
   could take a couple of minutes if the tracker is down or very busy.
   (Only one attempt is made, so the client will exit even if the
   connection fails.)

   If Ctrl-C or kill is used a second time, the client closes all peer
   connections and exits without waiting for the tracker connection. This
   means that other peers may still attempt to contact you for a while,
   and the tracker may not accept you back into the torrent until your
   original session expires. (This could take up to a couple of hours,
   depending on the tracker.)

   In either case, this is a clean shutdown of CTorrent. All downloaded
   data is written to disk before exiting. (Though only complete pieces
   really count if the torrent is restarted, as there is no way to know
   which blocks are missing from partial pieces.)
     _________________________________________________________________

References

   1. http://www.rahul.net/dholmes/ctorrent/
   2. http://en.wikipedia.org/wiki/BitTorrent
   3. http://btfaq.com/
   4. http://www.rahul.net/dholmes/ctorrent/userguide.html#opt_general
   5. http://www.rahul.net/dholmes/ctorrent/userguide.html#opt_download
   6. http://www.rahul.net/dholmes/ctorrent/userguide.html#opt_create
   7. http://www.rahul.net/dholmes/ctorrent/userguide.html#examples
   8. http://www.rahul.net/dholmes/ctorrent/userguide.html#commands
   9. http://www.rahul.net/dholmes/ctorrent/userguide.html#opermenu
  10. http://www.rahul.net/dholmes/ctorrent/userguide.html#bwlimits
  11. http://www.rahul.net/dholmes/ctorrent/userguide.html#startup
  12. http://www.rahul.net/dholmes/ctorrent/userguide.html#status
  13. http://www.rahul.net/dholmes/ctorrent/userguide.html#stopping
  14. http://www.rahul.net/dholmes/ctorrent/userguide.html#-a
  15. http://www.rahul.net/dholmes/ctorrent/userguide.html#-A
  16. http://www.rahul.net/dholmes/ctorrent/userguide.html#-b
  17. http://www.rahul.net/dholmes/ctorrent/userguide.html#-c
  18. http://www.rahul.net/dholmes/ctorrent/userguide.html#-c2
  19. http://www.rahul.net/dholmes/ctorrent/userguide.html#-C
  20. http://www.rahul.net/dholmes/ctorrent/userguide.html#-d
  21. http://www.rahul.net/dholmes/ctorrent/userguide.html#-D
  22. http://www.rahul.net/dholmes/ctorrent/userguide.html#-e
  23. http://www.rahul.net/dholmes/ctorrent/userguide.html#-E
  24. http://www.rahul.net/dholmes/ctorrent/userguide.html#-f
  25. http://www.rahul.net/dholmes/ctorrent/userguide.html#-i
  26. http://www.rahul.net/dholmes/ctorrent/userguide.html#-I
  27. http://www.rahul.net/dholmes/ctorrent/userguide.html#-l
  28. http://www.rahul.net/dholmes/ctorrent/userguide.html#-m
  29. http://www.rahul.net/dholmes/ctorrent/userguide.html#-M
  30. http://www.rahul.net/dholmes/ctorrent/userguide.html#-n
  31. http://www.rahul.net/dholmes/ctorrent/userguide.html#-p
  32. http://www.rahul.net/dholmes/ctorrent/userguide.html#-p2
  33. http://www.rahul.net/dholmes/ctorrent/userguide.html#-P
  34. http://www.rahul.net/dholmes/ctorrent/userguide.html#-s
  35. http://www.rahul.net/dholmes/ctorrent/userguide.html#-s2
  36. http://www.rahul.net/dholmes/ctorrent/userguide.html#-S
  37. http://www.rahul.net/dholmes/ctorrent/userguide.html#-t
  38. http://www.rahul.net/dholmes/ctorrent/userguide.html#-T
  39. http://www.rahul.net/dholmes/ctorrent/userguide.html#-u2
  40. http://www.rahul.net/dholmes/ctorrent/userguide.html#-u
  41. http://www.rahul.net/dholmes/ctorrent/userguide.html#-U
  42. http://www.rahul.net/dholmes/ctorrent/userguide.html#-v
  43. http://www.rahul.net/dholmes/ctorrent/userguide.html#-x
  44. http://www.rahul.net/dholmes/ctorrent/userguide.html#-X
  45. http://www.rahul.net/dholmes/ctorrent/userguide.html#-z
  46. http://www.gnu.org/software/screen/