qBittorrent official forums

Hi , there I'm Jeremy.

Very often (not always) I would try downloading a torrent which has at least several seeds, but my client would only connect to 1 or 2, and sometimes none.  What could be causing this?  Is it a setting on their end?
What's even weirder is that recently, a friend of mine (from another country) who is also using qB, started downloading a torrent which I am seeding, but for a long time we did not connect.  For many days he was nly connected to 1 or 2 other seeds, downloading at suboptimal speeds.  My qB was relatively inactive, so its not like I had reached some maximum number of connections or anything.  I had almost nothing happening in qB.  Why wouildn't qB connect me to him?  What could be possible reasons?

Only when he reached about 90% of the rather large torrent, we got connected and I was transferring to him (I saw him in the peers list). 

For some reason the torrent network is not optimally utilized.  Is this a client issue, protocol issue, or what? 
When I don't connect to seeds, I tend to think it's something on their end.  But when I know for a fact that someone is downloading at low speeds something that I am trying to seed, and its not connecting us, then I know something must be wrong. 
I have my qB port forwarded and I pass a port check.  Win 7 x64, qB 4.1.1
ufabet
Any help would be great.
Thank in advance.

At the start of the torrent, many of the ips attempted can be for peers+seeds that are dead-and-gone or just "hopelessly" firewalled (they block all connection attempts to them).

A tracker may be handing out a list of ips for peers+seeds, but many of those peers+seeds may no longer be active. Do check that your qBT is getting tracker updates correctly. (no error messages in the trackers tab for a torrent)

There's also many torrents with multiple trackers...and the trackers themselves can be dead-and-gone so if qBT isn't trying multiple trackers it may get 'stuck' on a dead one.
Worse, qBT attempting all the trackers at once can cause any tracker that has multiple attempts to it too quickly to start blocking your ip instead of handing out peer ip lists. So if a torrent has both a http and utp (or even https) tracker URL to the same tracker server then qBT is supposed to only use ONE of those at a time.

This inability of 2 peers to connect to one another can be due to there being lots of peers+seeds on the torrent that finding a particular one (your friend) may be difficult.
Oh, I forgot another reason -- if either of 2 peers "fills up" with other connections first (at connection max for per torrent OR globally), then it won't make a connection.

Packet loss may cause a working peer-to-peer connection to break and those may not reestablish very often, like only reattempted once every 1-60 minutes (the delay may increase as more disconnects occur).

Packet corruption can even cause peers to BAN one another and then not connect to each other until the bans are cleared, usually by restarting the BitTorrent software.
This should be a far rarer event than simple packet loss ...but I've seen peer connections to/from qBitTorrent to do this even in my local loopback tests -- qBT would get banned for piece hash failure/s.
At least 1 of the bugs in qBT (or rather libtorrent) that might cause packet corruption was recently fixed in the last year...so qBT v4.1.2 should be less likely to have this problem than v4.0.3 or even v3.1.16 ...in theory.
Someone probably should do more testing on that matter.