I'm using the latest version of Ubuntu and Transmission.

According to Transmission, the file I am downloading has 0 peers and is idle, even though there are a few peers seeding it.

Here's a batch of error messages from Transmission's log:

> Could not connect to tracker. Tracker gave HTTP response code 503, 504

This is the firewall's status:

> To                         Action      From

--                         ------      ----

51413/tcp                  ALLOW       Anywhere

51413/udp                  ALLOW       Anywhere

51413/tcp                  ALLOW       Anywhere (v6)

51413/udp                  ALLOW       Anywhere (v6)

51413/tcp                  ALLOW OUT   Anywhere

51413/udp                  ALLOW OUT   Anywhere

25,53,80,110,443/tcp       ALLOW OUT   Anywhere

53/udp                     ALLOW OUT   Anywhere

67,68/udp                  ALLOW OUT   Anywhere

5050/tcp                   ALLOW OUT   Anywhere

51413/tcp                  ALLOW OUT   Anywhere (v6)

51413/udp                  ALLOW OUT   Anywhere (v6)

25,53,80,110,443/tcp       ALLOW OUT   Anywhere (v6)

53/udp                     ALLOW OUT   Anywhere (v6)

67,68/udp                  ALLOW OUT   Anywhere (v6)

5050/tcp                   ALLOW OUT   Anywhere (v6)

Also, Transmission says that port 51413 is open.