If you are not uploading, the tracker should slow your download to almost nothing.
Hmm, I did want to point out that this isn’t quite correct, and indicates a misconception. The tracker isn’t in control of, well, much of anything except swarm membership of that tracker. It is not the tracker that slows things down. Trackers are very simple beasts, and they have nothing to do with bittorrent transfers as such.
All of the piece transfers are directly from one client to another client. The tracker doesn’t control them, or know that they happened, or get involved in any way. Important to understand this: transfers of pieces go from your client to my client directly. They do not go from your client to the tracker, and then to my client. The tracker is not involved.
Later, your client reports to the tracker how much it has uploaded and downloaded, but not to whom. Later, my client does the same. This happens during every tracker scrape. But the tracker never knows or has any way to learn, that you transferred anything to me, or I to you. And if you think about that, aren’t you glad that’s so!?
It is other clients that slow things down for the one which isn’t uploading. If one client has no pieces it will offer to trade, all of the others will snub that client in favor of others who will offer some.
I got ADSL 8mbit, I download stuff in about 850kb/s but the problem is I dont get any upload speed at all (It’s stuck at 0kb/s)… why is it like that ? Do I need to open any port or something in my router or what?
This is pretty strange. My first take on it would be a software firewall blocking BitComet outbound. You should definitely check that. Using more than one firewall often creates messes like this.
But if it were happening, then yes, your download speed should be pretty awful absent a whole lot of seeders in the swarm.
Have you tried seeding a torrent yourself? That would be a good experiment.