What ports does BitTorrent use? Will it work with a firewall/NAT?
The quick summary: You need to forward your ports if you have NAT in order to get the fastest speeds. This is probably the most common thing that people fail to do when using BitTorrent. Read on for more details of what all this entails, and if it’s something that you need to do. Prior to version 3.2, BitTorrent by default uses ports in the range of 6881-6889. As of 3.2 and later, the range has been extended to 6881-6999. (These are all TCP ports, BitTorrent does not use UDP.) The client starts with the lowest port in the range and sequentially tries higher ports until it can find one to which it can bind. This means that the first client you open will bind to 6881, the next to 6882, etc. Therefore, you only really need to open as many ports as simultaneous BitTorrent clients you would ever have open. For most people it’s sufficient to open 6881-6889.
Prior to version 3.2, BitTorrent by default uses ports in the range of 6881-6889. As of 3.2 and later, the range has been extended to 6881-6999. (These are all TCP ports, BitTorrent does not use UDP.) The client starts with the lowest port in the range and sequentially tries higher ports until it can find one to which it can bind. This means that the first client you open will bind to 6881, the next to 6882, etc. Therefore, you only really need to open as many ports as simultaneous BitTorrent clients you would ever have open. For most people it’s sufficient to open 6881-6889. The port range that BitTorrent uses is configurable, see the section (Xref) What are the command line parameters for the BitTorrent client?, specifically the –minport and –maxport parameters. The trackers to which BitTorrent must connect usually are on port 6969, so the client must have outbound access on this port. Some trackers are on other ports, however.
