Sartup Traffic

[ExcessTraffic]

I came to this forum today for the first time looking for answers to a couple of questions, the main one being:

What is the unsolicited UDP traffic generated by uTorrent every time the application is started?

- The traffic always starts off as outgoing UDP to 72.20.34.145:6881;

- All following outgoing UDP traffic is to various other IPs / ports (a quite substantial number);

- The traffic occurs even when "Check for automatic updates" is unchecked in options (so that should not be what the traffic is about);

- The traffic occurs even when there are no torrents started;

- The traffic occurs even when no torrents are loaded at all in the application;

- The remote ports are predominately above 5000, but I have seen some between 1500-2000 (not really that important).

To my surprise and delight, I saw that someone else had asked about the outgoing traffic earlier this morning, so I figured I would only need to follow that thread to find my answer.

However, to my chagrin, that thread was promptly closed. Although it appears that the OP of that thread may have sabotaged his own effort to get an answer by being a little too "smart" with a moderator, I was alarmed that the topic, having very valid merits, was closed without resolution to the issue of the source / reason for the traffic. The suggestion, per the closed thread, that uTorrent is just trying to connect to uTorrent.com (or related servers) is not adequate based on my observation of the activity so far. However, I am certainly open to being convinced otherwise.

So again, in all my humble lack of knowledge, why does an application (uTorrent) generate so much outbound traffic upon start-up, especially considering the list of items I posted above.

Thank you ... and by the way, I am not the same person who posted about this topic in the other thread. He was banned. Hopefully, I won't be.

[DreadWingKnight]

The UDP traffic at startup is purely DHT bootstrapping.

[ExcessTraffic]

Per the FAQ link you originally posted in the aforementioned, closed thread:

http://utorrent.com/faq.php#Help.21_.C2.B5Torrent_is_sending_e-mails.2Faccessing_the_web.2Fetc.21

Help! µTorrent is sending e-mails/accessing the web/ etc!

<snip>

It also connects to router.utorrent.com if you have DHT enabled. This is REQUIRED for the functionality of DHT (at least the first start). If you block it, DHT may not function!

I read that FAQ prior to posting, but I did not understand that the connection(s) (router.utorrent.com?) would occur at start-up and result in 100s (1000s) of connection attempts to 10s and 10s (hundreds?) of unique IPs, especially given the fact that no torrents were started or even loaded in the application. I've not used BitTorrent much, and I didn't pay much attention to the start-up traffic when previously using Azureus on a Linux machine (if any start-up traffic occurs at all), so I have no concept of how ubiquitous this DHT bootstrapping process is amongst other clients.

But indeed, disabling DHT in uTorrent silences all the questioned traffic.

Thank you very much for the quick response.

[DreadWingKnight]

UDP traffic is a connectionless system.

Any program reporting UDP traffic as connections is misreporting.

[ExcessTraffic]

Sorry.

I was just trying to convey that LOTS of UDP traffic was occurring at uTorrent start-up, but in so doing, I failed to be careful with the exact wording in a part of my post. "Connection(s)" was not accurate, as you say.

Thanks again.