Enhanced CTorrent User's Guide
This guide is presented to offer additional information related to using
Enhanced CTorrent.
This document is not an introduction to BitTorrent--for that, try
this,
this, or an Internet search.
Contents
Options Index
-a
-A
-b
-c
-c
-C
-d
-D
-e
-E
-f
-i
-I
-l
-m
-M
-n
-p
-p
-P
-s
-s
-S
-t
-T
-u
-u
-U
-v
-x
-X
-z
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.
-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
screen instead of using -d.
If this option is specified twice (-dd) then redirected standard I/O
descriptors will not be closed.
-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.
- 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 file_or_dir_to_upload
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.
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
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.
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.
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.
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.
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.)