Frequently Asked Questions

My software firewall told me BitComet is trying to send or receive email, what the hell??

Someone is using port 110 (POP3) or 25 (SMTP) for their Listen Port, so BitComet is connecting to them on that port to transfer the files you're downloading/uploading. Since these ports are reserved, your firewall assumes it's for email.

It's most likely somebody behind a firewalled network (corporate or an educational institution etc) trying to use any open port they can to acheive good speeds. It's nothing sinister, just a poor assumption by your firewall software.

A torrent task stays at 0.00% (won't start) and is displaying only 'connecting' status icons ( or ), why?

The tracker is most likely offline so BitComet cannot connect to it to start your download. Check the Trackers section (bottom left of BitComet) and see if it's displaying an error message. A good response is "Tracker return xx peers", with xx being higher than 0.

If you received a favourable tracker response, take a look at the Health & Seed/Peer[all] columns on the right of the torrent task... if the health is below 100% or it's showing very few or no seeds/peers, there's a high chance the torrent won't start and/or won't be able to finish because nobody is sharing the data you need.

Either way you should first try downloading the torrent from isohunt.com because they have a system where if a tracker goes offline it automatically adds backup trackers (if any) that other people are using. Also ensure DHT is enabled by right-clicking the torrent and selecting Properties then the Advanced tab and ticking "Enable Public DHT Network".

If a couple of days have passed and there is no change, try to find the same torrent on a different tracker and resume it. Failing that, you may have no choice but to download the files via a different P2P application/network.

If you can't ever connect to any tracker (try several that you know are active and well seeded), a firewall or other application may be blocking BitComet from the internet. For software firewall configuration information, see #2 here.


Related FAQ topics:
° A torrent stopped at xx% and is either only uploading or not uploading/downloading at all, why?
° A torrent is stuck at 99.x% and still downloading (rubbish data), why won't it finish?

Why are other internet applications slow or don't work (time out) when BitComet is running?

Your download/upload speeds are finite, so when you're downloading/uploading quickly with one application there may not be enough bandwidth left for other applications to function properly.

° Limit your download speed a few KB/s below the maximum possible.
Options > Preferences > "Global Max Download Rate"

° Limit your upload speed to 80% of the maximum possible (see #3 here).

° Your maximum half-open connections limit could be being reached (see here).

° Your "Maximum Connections per task" and "Connections to keep per task" could be set too high (see #4 here).

° Ensure your port forwarding is configured properly (you should see both Local and Remote initiated connections in the Peers section).

What is Peer Info Exchange / Peer Sharing?

In the old days, when a tracker went offline all the peers downloading/uploading would be stop very quickly. They would then have to wait until the tracker came back online to start downloading/uploading again.

With the get_peers/peers extension (Peer Info Exchange), peers can continue to download/upload when a tracker goes offline by broadcasting their peer lists to other peers. This is fantastic for sharing as it strengthens BitTorrents weakest link - trackers. It can also reduce the load on trackers.

Private ratio trackers have not always seen this as a good thing however. In the early implimentation of this feature it was possible for private peer lists to be shared with clients on public trackers - which is what got BitComet banned from many trackers (see here). But with the release of BitComet v0.59, the SecureTorrents ('private' flag) method of disabling Peer Info Exchange and DHT has been supported, so these features can be disabled within a torrent or in a tracker response (announce). This is the same method Azureus uses.

How do I create a new torrent (share a file I have with others)?

Instructions can be found here. It's also recommended that you read this.

What do UPnP, ICS and ICF mean, and how do they affect me?

UPnP = Universal Plug and Play
BitComet can use UPnP to automatically open/forward a listen port for incoming connections in your router for you, but for this to work your router needs to support UPnP (and have it enabled) and UPnP must be enabled in Windows XP or better - older Operating Systems don't support UPnP.

UPnP is enabled by default in BitComet, Windows XP and most routers, so if you see a "UPnP Device not found" error in BitComet's Log (the Log can be found at the bottom left corner of BitComet), you'll fall into one of these groups:

- You're only using a modem (not a router).
Port forwarding isn't required for modems because no ports are blocked, so just disable UPnP in BitComet.

- Your Router and/or Operating System either doesn't support UPnP or UPnP is disabled.
Either re-enable it or configure port forwarding manually (see #1 here).

The option to enable/disable auto port mapping via UPnP can be found here:
Options > Preferences > Advanced > Connection > "Enable UPnP Port Mapping"

ICS = Internet Connection Sharing
BitComet can automatically configure ICS to allow incoming connections to be passed from the host computer to the client computer. If you use ICS, it's strongly recommended that you take advantage of this feature.

Note: You only need this option enabled if BitComet is being run on the client computer. i.e. you're connecting to the internet through a different computer that it is running ICS.

The option to enable/disable auto configuration of ICS & ICF can be found here:
Options > Preferences > Advanced > Connection > "Enable NAT/Firewall Configuration in ICS/ICF"

ICF = Internet Connection Firewall
BitComet can automatically configure Windows Internet Connection Firewall (known as 'Windows Firewall' in XP SP2) to allow incoming connections on BitComet's Listen Port. If you use the default Windows firewall, it's strongly recommended that you take advantage of this feature.

If you use a different firewall or wish to configure the Windows firewall manually for BitComet, see #2 here.

The option to enable/disable auto configuration of ICS & ICF can be found here:
Options > Preferences > Advanced > Connection > "Enable NAT/Firewall Configuration in ICS/ICF"

In the Peers section I see some NAT Traversal initiated connections, what does this mean?

Here is an extract from the BitComet website:
"Non-firewalled clients and clients on publicly routable IP addresses are able to help NATed users to communicate while downloading the same files. BitComet does an even better job for users behind NAT, by enabling users behind NAT, to connect to each other via UDP. That means the download rate will increase because it can now connect to more peers. Without any configuration, BitComet will auto detect your internet connection ( to find out if you are behind the NAT ) and does this automatically. You may enable or disable this feature in the Options ->Connections->Port Mapping dialog.

Note: Not all versions of BitComet currently support NAT Traversal "

NAT Traversal (UDP) is slower than standard TCP connections, so you should only be using it if you need it.

If you're behind a network that you're unable to configure for BitComet (corporate, educational etc), NAT Traversal may be the only way to connect to others. So ensure the following option is Enabled or set to Auto Detect:

Options > Preferences > Advanced > Connection > "Use NAT Traversal via UDP" [ENABLE] or [AUTO DETECT]

If you're behind a network that you're able to configure for BitComet, you should see none or very few NAT Traversal connections. If you're seeing a large amount of NAT Traversal connections or only Local and NAT Traveral connections (no Remotes), something may be blocking your TCP traffic, so see steps 1 & 2 here. BitComet may also be incorrectly detecting your need for NAT Traversal, so ensure the following option is Disabled:

Options > Preferences > Advanced > Connection > "Use NAT Traversal via UDP" [DISABLE]

Can I schedule my downloads to start at a certain time?

BitComet does not have a built-in scheduler in the older versions, but it's very easy to schedule downloads by doing the following...

- Enable the following setting in BitComet:
Options > Preferences > Appearance > "Auto-resume tasks on BitComet startup"

- Start up the torrent task(s) you want BitComet to download later, then close BitComet while the tasks are running (just click the X in the corner).

- Use a freeware application like Freebyte Task Scheduler to schedule the time you want BitComet.exe start.

When BitComet automatically starts up at your chosen time, it will continue downloading any tasks that were running when you closed it previously.

What ports does BitComet use?

• WARNING: Do NOT forward port 6881 or 6881-6889 from your router! They're the default port range for the official BitTorrent client (Not BitComet!). BitComet does NOT and has not ever used those ports, so simply opening/forwarding port 6881 and/or 6881-6889 will NOT increase your BitComet speeds or make you connectable. In addition, many ISPs and trackers will block (and possibly ban) users on those ports, so even if you were using the official BitTorrent client instead of BitComet, you still shouldn't use those ports!

BitComet uses only one single port number (assigned randomly during installation) for incoming/remote "Listen" connections, which can be located or modified here:

Options > Preferences > Connection > "Listen Port"

It's best to use a listen port between 49152 and 65534 because they're classed as "Dynamic and/or Private Ports" by IANA, so other applications rarely use them by default and they're not the standard ports blocked by ISPs or trackers, but you can use any other port you wish. To avoid any conflicts it's strongly recommended that you do not use a port within the "Well Known Ports" range (1-1023), the Ephemeral port range (1024-5000), the default BitTorrent port range (6881-6999) or any other port listed on this page. Again, it's best to simply choose any port number within 49152-65534.

BitComet.exe needs access through the following ports:

TCP
Local Ports (Outgoing Traffic): 1024-5000
Local Ports (Incoming Traffic): your chosen Listen Port
Remote Ports (Outgoing Traffic): All
Remote Ports (Incoming Traffic): All

UDP
Local Ports (Outgoing Traffic): your chosen Listen Port
Local Ports (Incoming Traffic): your chosen Listen Port
Remote Ports (Outgoing Traffic): All
Remote Ports (Incoming Traffic): All

Instructions on how to configure many hardware or software firewall(s) can be found here and here, or read your user guide. Port forwarding instructions (for routers) can be found here.

Note: UDP is required for the Distributed Hash Table feature (aka "Trackerless"). If you're not using DHT then you only need to forward ports for TCP traffic. The Listen Port entered in BitComet is the same port number used for both TCP & UDP.

My upload speed is slow, how can I increase it?

Keep in mind that if you're using a private tracker that has lots of seeds and very few peers, it may be impossible to upload quickly. There will need to be lots of peers to take the data you're trying to upload. This is also the case if some of the seeds have very fast connections - the peers may simply not need the data you're trying to upload.

° Increasing the amount of Upload Slots will allow you to upload to more clients at once which often increases upload speeds. These options can be found here:

Options > Preferences > Advanced > Connection > "Global maximum upload slots"
Options > Preferences > Advanced > Connection > "Global minimum upload slots"

° Increase your minimum upload speed:

Options > Preferences > Task > "Minimum upload rate per task"

° Set the task to a higher priority. Right-click the torrent task and select Priority > High

° If your speeds are slow while seeding, try increasing your minimum seeding speed:

Options > Preferences > Task > "Minimum upload rate per seeding task"


Also make sure your port forwarding is configured properly.

Re-start BitComet after making these changes.

The torrent is supposed to be xxMB but I've downloaded xxMB (greater than the actual size), why does it do this?

There can be several reasons why this is happening, all of them normal and will happen with any client - it's just how BitTorrent works. The only difference between BitComet and most other clients is BitComet will show you how much data it has actually downloaded (#1, #2 and #3 below), where most other clients will only show you to data that has been saved or discarded due to failed hash checks (#1 and #2 below).

One of the following three possibilities happens when BitTorrent/BitComet receives a piece of data and checks it...

1) The data hash checks fine so is written to the disk.

2) The data fails the hash check (data is corrupt, incomplete or other ways unusable) so is disarded. When this happens the data will simply be requested and downloaded again. This amount is displayed as "rubbish data dropped" in the Summary section.

3) The data does not match the request, so it's discarded. This doesn't mean the data was bad, it just means it wasn't what BitTorrent/BitComet requested so it has to be thrown away (it's just how it works). The other client may have sent the wrong data or BitTorrent/BitComet doesn't know what to do with it. When this happens the correct data will be requested until the data matching the request is received.

In addition to this, there are also ACKs going on behind the scenes. For each packet of data that is received, BitTorrent/BitComet must send an acknowledgement packet to say the data has been received and is ready for the next one to be sent. This is just how TCP networking works. Although these packets are very small, they do add up.

If this is unacceptable to you, and judging from some posts about this subject a few people seem to think it is, it's recommended that you use a different method to download your data (HTTP. FTP etc) because this is an unavoidable fact of how the BitTorrent protocol works.

Changing clients won't cause you to download less bad or unrequested data, most of them just won't display how much you've actually downloaded. But you can do the following to attempt to minimize this amount...

° Use an IPFilter to stop your client from downloading from locations that are known to be bad and may force bad data upon you. Instructions for using an IPFilter for BitComet can be found here, or you could use PeerGuardian 2 (recommended) to block them from all your applications (not just BitComet).

° Limit the amount of peers you're connecting to. If you're connected to a giant swarm it makes sense that you'll receive more data that is bad or has not been requested, so although you may gain a few kB/s when connecting to several hundred peers, you may be dumping much more data and you're actually at a loss. The amount of peer connections can be adjusted here:

Options > Preferences > Connection > Advanced > "Maximum Connections per task"
Options > Preferences > Connection > Advanced > "Connections to keep per task"

Everything I change in the Preferences keeps reverting back to what it was (won't save), why?

Something has most probably marked BitComet's configuration file as read-only, so changes cannot be saved. To fix this, go into your BitComet install directory (usually a sub directory in C:\Program Files\) then right-click your BitComet.xml file (or BitLord.xml for BitLord) and select Properties. Then uncheck the 'Read-only' Attribute box before clicking OK.

(Edit to add:) In Windows XP and later versions, this can also be caused by not having write-permission in that directory.

How can I preview a movie before it's finished downloading (incomplete)?

BitTorrent/BitComet isn't like some of the older P2P networks that simply download files from start to finish, it instead breaks the files up into many small pieces and downloads them from multiple sources in a random order, then it puts all the pieces back together again in the correct order to create the finished files. This is fantastic for getting the data, but the unfortunate downside is files generally cannot be opened/played while they're incomplete -- even if you have 99% of the file you may still be missing a crucial part required for it to work.

Clicking the Preview button on BitComet's toolbar should be your first course of action. The inbuilt preview function (first introduced in BitComet v0.60) will attempt to download the pieces of the file then put them in the correct order before using a special application & codec to play/preview the reconstructed video file. This isn't always possible because some formats cannot be previewed this way or the pieces of the file required may not be available.

If that doesn't work, you could try previewing them with good a media player. Some people have reported varying success previewing partially downloaded video files (AVI, MKV, MPEG1, MPEG2, OGM etc) with VLC media player, BSplayer and/or AVIpreview.

If it's an MPEG-4 (AVI) file, the ffdshow codec could further improve your odds, and if the media players above didn't do the trick you could also try using DivFix.

Before attempting to preview a file, make sure you either stop the torrent task or copy the files to a different location on your hard drive and open them from there, otherwise you may get a "file currently in use" error message because BitComet requires full access to the files while downloading/uploading. You may also need to rename them to remove the .bc! extension, depending on which media player you're using, and if you have the "Add .bc! extension for incomplete files" option enabled in Options > Preferences > Task.


Additionally, it's worth mentioning that a guide written by D-503 contains detailed instructions on what software is required to open/play/use most common file types. So if you don't know how to open whichever format your files are in, or are not happy with your current application and want to find a new one, chances are this guide will offer some insight: "A Handy Guide To Using The Files You've Downloaded"

Thanks to rafi_d for mentioning AVIpreview (original thread here).

NOTE: File types like RAR/ZIP/ISO (etc) cannot be used unless they're 100% complete. The methods mentioned above should only be used for single audio or video files. e.g. AVI/MPG/VOB/MP3 etc

How do I upgrade to a new version of BitComet (or downgrade to an old version)? Can I keep my existing settings?

It's extremely simple, all you need to do is shut down your BitComet then install the new version straight over the top of the old version (simply choose the exact same install location). BitComet will import your existing settings and torrents, so you can immediately open up the new version and continue downloading from where you left off.

Downgrading to older versions is done the exact same way.

You can download new and old versions of BitComet from the the official P2PForums.com mirror thread or the archive section of the BitComet website