ZTE ZXDSL 931WII router and utorrent NOT playing nice.

- TCPip driver might be hitting the connection limit set in your registry.
- connections have to undergo a wait timeout after a disconnection
I don't recall how long the default is (30 seconds or 300 seconds).

- Some ISP have software that will slow your connection down if they think you use too much bandwidth over short period of time. they can do this over small time windows and remove your limits real time over short windows of say 30 mins. They want to slow your band bandwidth usage but want to keep you connected so you will not generate a support call to them which costs them money.


Anyway, the driver will block new connections until the wait timeout expires even if all the connections have been closed. This was implemented to slow down malware and to help limit torrents that were running without the machines owners knowledge.

for example: say 200 total connections allowed, you do the following
start 100 connections : works as expected
start another 100 connections : works as expected
start 1 more connection: fails because connection limit reached
stop 100 connection: works as expected (you now have 100 active connections and 100 wait pending connections being closed down)

now attempt to start 1 connection and it fails because your connection limit has been reached. 100 active connections and 100 pending close connections in the wait time out state.

How to fix: if you really want to share your torrents there should be a registry settings the total number of connections and the wait timeout period best to google for the the settings.

Thank you for your very insightful post!

Some more info on my post : I am running Win7 64-bit SP1 and I was told I need not concern myself with TCP patches since it's something Windows handles automatically.

Furthermore, my ISP is not running any software of any kind to impede my connection.

Net works just fine, I open up uTorrent on idle, it still runs fine. I add a single torrent to it, it all collapses.

Since I don't have your tech savvy, could you suggest in fairly layman's terms a few more solutions to this?

I tried lowering concurrent connections to a ridiculous 10 or so (From the inital 200) but it still wouldn't work.

Any help would be greatly appreciated  

run cmd.exe with administrator privileges
type the command
netstat -a

it will indicate each connection and its state
you will see each connection starting point and ending point and state

for example: 192.168.1.111:139
would be the local IP address of my machine 192.168.1.111
then a : then the port number (socket number that is being used to track the connection)

then the second address is the ip address of internet machine you are connected
and its port number it uses to identify your connection.

last will be the state of the connection LISTENING, ESTABLISHED, CLOSE_WAIT, TIME_WAIT

http://support.microsoft.com/kb/137984 has a table of what each state means

run the tool before you start your torrent, then see what happens while it runs, then after you close the torrent. the connections dont' get cleaned up for a while.

if you open an close a bunch of connections in a short period of time you will end up
with a bunch of connections in TIME_WAIT state for several minutes. This can prevent further connections depending on your max number of connections allowed by your TCP transport driver. This we are not talking about the number of connections used by your torrent software.
also, bugs can really mess this whole scheme up. bugs in the transport, bugs in the network card, bugs in the router, bugs on the other guys machine transport, his netcard. the whole round trip path from your machine, across your hardware, your IPS hardware, the internet backbone, into some other ISP, to someones cable modem, router, ethernet card, ethernet card driver, tcpip driver, OS and to their copy of torrent software. then back, and it is not the same path.

first get your torrent to make one connection thru your firewall and router. there will have to be a port open to do that. you will have to look at your software to see what port it needs to open.

Terrific post! Ok, I went to cmd and did as you told me.

It dumped a bunch of active connections and two pertaining to uTorrent ( I spotted that by the port number used). The first one was TIME_WAIT and then it threw in another as LISTENING and then nothing....torrent was unresponsive, but at least the rest of my internet didn't crash horribly.

I filed a complaint with my ISP and they answered that there's some issue with my phone line and that they're looking into it. It sounds like BS to me though. If there was an issue, I wouldn't have internet at all, right? This is clearly something to do with utorrent...

i have the exact same problem.. did you find a solution??

Νο solution whatsoever sadly, after two visits from the in-house technician. Using Tixati torrent client I can download some stuff with a very incosistent rate and the internet coming and going during the download, definitely not a permanent solution.

They told me to give them till Monday to fix it and if they do nothing by then, I'm going back to simple, plain old DSL and my trusty LinkSys router!

I was expecting a bunch of connections in TIME_WAIT (50 or so). It sounds like some of your connections are blocked. maybe by the windows firewall, or the ports not being forward in your router. Sometimes cable modems get "confused" and you can hit the reset and have the cable company automatically re-download its configuration info. If the cable company is blocking your port, you can configure your torrent for another port (less well known one) and it takes 15 mins before their software detects the usage spike and blocks you again. (at least that helps you figure out the problem)
sometimes cached DNS data is messed up and you can run
IPCONFIG.exe /flushdns to clear things out and try again.
Also, I do think under the new rules if the provider detects unlawful file sharing they can block your port but this is unlikely. All else fails you can just install microsoft
network monitor and watch all the network traffic and see where it is being rejected. I have seen cases where there were bugs in the cards network driver, each time you tried to send some packets the connection would be reset because of the bug. I did not find those until I did a sniffer trace with network monitor. the last 2 times I found that it was in a laptop network card (Atheros) both times I updated the driver and no connection resets and all worked as expected.