Why can I upload when my VPN doesn't support port forwarding?

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nothingreally
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Why can I upload when my VPN doesn't support port forwarding?

Post by nothingreally »

This is just a matter of curiosity rather than a concern. I always try at least not to be a complete leech considering that it endangers the filesharing community, but for some reason, even behind a VPN that doesn't support port forwarding, I somehow seem to be able to upload a certain amount, enough to get at least a 1/1 ratio so I can just seed the torrent up to the proper ratio that I'm not just a leech.

I just have to leave the client open, but much longer than it took to download.

How does this work? Is there a way to make it better and actually use a VPN while not just being a leech?
gderf
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Re: Why can I upload when my VPN doesn't support port forwarding?

Post by gderf »

It works because the endpoint of your VPN has ports open that peers can connect to.

You would need a VPN port forward if you wanted to run a service on your end of the tunnel and make it available via the VPN IP address instead of your own IP address.
Switeck
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Re: Why can I upload when my VPN doesn't support port forwarding?

Post by Switeck »

Your VPN can make outgoing connections to peers that are not firewalled...and it is to those that qBitTorrent is able to upload to.

There is also a remote possibility that uTP's STUN-based hole-punching works even through the VPN, but that requires VPN support for conditionally opening UDP ports at its IPv4 location and even some luck.
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