Network

Does BitTorrent Mainline work well on Windows XP SP2 or higher operating systems with an unpatched TCPIP.sys?

Yes, by default, BitTorrent Mainline will make at most 8 simultaneous connection attempts to work within the 10 connection attempt (half-open connection) limit on these operating systems.

Patching TCPIP.sys to a higher limit may help if you are having problems with your Internet connection, though increasing the limit may also cause some routers to freeze up (due to the increased rate of simultaneous connection attempts). If you would still like to patch the file, download the EventID 4226 Patcher from LvlLord.de.

Beware that you should refrain from setting the TCPIP.sys limit to any number greater than 50, as there are few (if any) benefits to be gained from higher numbers. Also understand that net.max_halfopen should always be set to a number lower than the TCPIP.sys limit set by the patcher (at most 80% of the TCPIP.sys limit only).

Microsoft has made a habit of reverting the TCPIP.sys connection attempt limit through Windows Update, which (for many users) occurs on a monthly basis. If you decide to patch your TCPIP.sys file and raise the net.max_halfopen limit along with it, then remember to repatch the file every time you perform a Windows Update (otherwise, you'll most likely run into connection troubles).

How can I tell if a peer is an incoming or outgoing connection?

You can check the Flag column in the Peers tab for the peer.

How do I change the number of active torrents jobs or downloads allowed to run simultaneously?

Change the queue settings. It is recommended that you not modify this setting unless you understand very clearly what the consequences are behind changing this setting. Starting too many torrent jobs simultaneously can be detrimental to bandwidth usage, so if you are not certain about your changes, stick to the numbers recommended by the Speed Guide.

How do I change the number of connections BitTorrent Mainline uses?

Set the relevant options in the preferences. It is recommended that you not modify this setting unless you understand very clearly what the consequences are behind changing this setting. Starting too many torrent jobs simultaneously can be detrimental to bandwidth usage, so if you are not certain about your changes, stick to the numbers recommended by the Speed Guide.

How do I change the port BitTorrent Mainline uses?

The listening port for incoming connections can be set with the Port used for incoming connections option in the Preferences. For outgoing conections, BitTorrent Mainline uses the ephemeral port range by default, but this can be changed by using the net.outgoing_port and (optionally) net.outgoing_max_port options.

How do I forward ports?

Read the Port Forwarding guide.

How do I hide my IP address?

You don't. BitTorrent wasn't designed with anonymity in mind. Because it requires that peers know each other's IP addresses to transfer with one another, spoofing or hiding your IP address won't do you much good with regards to speed and/or connectivity.

VPN or proxy services may allow you to masquerade your IP address behind other IPs, but because they act as middlemen, you are effectively firewalled behind such services, which is a bad thing.

How do I make BitTorrent Mainline report a different IP to the tracker? I'm behind a proxy and need this function.

Set the IP/Hostname to report to tracker option in the Preferences.

How do I make BitTorrent Mainline use a different upload speed when seeding?

Set the Alternate upload rate when not downloading option in the Preferences.

How do I make BitTorrent Mainline use a specific network adapter?

Set the net.bind_ip option to the IP address of the adapter you wish to use for incoming connections. Set the net.outgoing_ip option to the IP address of the adapter you wish to use for outgoing connections.

What port should I use for BitTorrent Mainline?

It is generally recommended that you not pick ports in the 6881-6889 range, as they are commonly throttled by ISPs. Since no single port has inherent advantages over any other port, you can simply let BitTorrent Mainline pick a random port for you.

Why am I still receiving incoming connection attempts after I have already closed BitTorrent Mainline?

In BitTorrent, peers disconnect from the swarm without notifying every other peer in the swarm because it would be inefficient to do so, and also because peers rarely have the IPs of every other peer in the swarm (which would make it impossible to do in the first place). Because most BitTorrent clients cache peer information, when they try to connect to a particular peer in their cache, they may end up attempting to connect to a peer that has already disconnected since they last received the peer's IP and port number.

This phenomenom is what you are observing when you see incoming connection attempts after you've exited BitTorrent Mainline. Depending on how many peers had a copy of your IP and port number in their peer cache, this can take up to several weeks to subside. Having DHT enabled may magnify the effects, as there are many more peers using DHT than there are connected to any one particular torrent swarm (so more users may have your IP and port number by the time you disconnect). Although there is no way to prevent this from occurring, disabling DHT may reduce the amount of time needed for this to taper off. Assuming your network is properly protected, these connection attempts can be safely ignored.