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> you need a machine that can handle whatever link speeds you need I would have expected the relay server only being used for initial handshake to punch throug

> you need a machine that can handle whatever link speeds you need I would have expected the relay server only being used for initial handshake to punch through NAT, after which the transfer is P2P. Only in the case of some network restrictions the data really flows through the relay. How could they afford running the free relay otherwise?

lotharrr 2y ago
There are two servers. The "mailbox server" helps with handshakes and metadata transfers, and is super-low bandwidth, a few hundred bytes per connection. The "transit relay helper" is the one that handles the bulk data transfer iff the two sides were unable to establish a direct connection. I've been meaning to find the time to add NAT-hole-punching for years, but haven't managed it yet. We'd use the mailbox server messages to help the two sides learn about the IP addresses to use. That would increase the percentage of transfers that avoid the relay, but the last I read, something like 20% of peer-pairs would still need the relay, because their NATs are too restrictive. The relay usage hasn't been expensive enough to worry about, but if it gets more popular, that might change.
- bscphil 2y ago
  The folks on the wormhole-rs fork (who appear to share your Github organization? [1]) already have NAT punching working 95+% of the time in my testing, so maybe what they're doing could be ported over to the Python implementation. [1] https://github.com/magic-wormhole https://github.com/magic-wormhole
  - Fnoord 2y ago
    The Rust implementation on Tailscale worked well for me. Except on a layer 7 firewall have to be quick to permit the connection or else it tries fallback.
  - meejah 2y ago
    That is just using normal STUN/TURN via another server that one of those developers is running
from-nibly 2y ago
You cant make a p2p connection over a NAT without exposing a port on the public side of the NAT.
- t0mas88 2y ago
  You can: https://en.wikipedia.org/wiki/Hole_punching_(networking) https://en.wikipedia.org/wiki/Hole_punching_(networking)
- voxic11 2y ago
  You aren't guaranteed to be able to do that but in practice most times you can.
- kccqzy 2y ago
  Go check out STUN and ICE. The best article I've found about NAT traversal is this article from Tailscale: https://tailscale.com/blog/how-nat-traversal-works https://tailscale.com/blog/how-nat-traversal-works
  - jvansc 2y ago
    https://sendfiles.dev/ https://sendfiles.dev/
    - yownie 2y ago
      is there a filesize limit for this?
    - kccqzy 2y ago
      That uses WebRTC, which uses the same NAT traversal tricks.
  - Fnoord 2y ago
    Not bad, though you don't even need STUN or ICE; https://github.com/samyk/pwnat https://github.com/samyk/pwnat https://github.com/samyk/slipstream https://github.com/samyk/slipstream

lotharrr 2y ago

There are two servers. The "mailbox server" helps with handshakes and metadata transfers, and is super-low bandwidth, a few hundred bytes per connection. The "transit relay helper" is the one that handles the bulk data transfer iff the two sides were unable to establish a direct connection. I've been meaning to find the time to add NAT-hole-punching for years, but haven't managed it yet. We'd use the mailbox server messages to help the two sides learn about the IP addresses to use. That would increase the percentage of transfers that avoid the relay, but the last I read, something like 20% of peer-pairs would still need the relay, because their NATs are too restrictive. The relay usage hasn't been expensive enough to worry about, but if it gets more popular, that might change.

bscphil 2y ago
The folks on the wormhole-rs fork (who appear to share your Github organization? [1]) already have NAT punching working 95+% of the time in my testing, so maybe what they're doing could be ported over to the Python implementation. [1] https://github.com/magic-wormhole https://github.com/magic-wormhole
- Fnoord 2y ago
  The Rust implementation on Tailscale worked well for me. Except on a layer 7 firewall have to be quick to permit the connection or else it tries fallback.
- meejah 2y ago
  That is just using normal STUN/TURN via another server that one of those developers is running

from-nibly 2y ago

You cant make a p2p connection over a NAT without exposing a port on the public side of the NAT.

t0mas88 2y ago
You can: https://en.wikipedia.org/wiki/Hole_punching_(networking) https://en.wikipedia.org/wiki/Hole_punching_(networking)
voxic11 2y ago
You aren't guaranteed to be able to do that but in practice most times you can.
kccqzy 2y ago
Go check out STUN and ICE. The best article I've found about NAT traversal is this article from Tailscale: https://tailscale.com/blog/how-nat-traversal-works https://tailscale.com/blog/how-nat-traversal-works
- jvansc 2y ago
  https://sendfiles.dev/ https://sendfiles.dev/
  - yownie 2y ago
    is there a filesize limit for this?
  - kccqzy 2y ago
    That uses WebRTC, which uses the same NAT traversal tricks.
- Fnoord 2y ago
  Not bad, though you don't even need STUN or ICE; https://github.com/samyk/pwnat https://github.com/samyk/pwnat https://github.com/samyk/slipstream https://github.com/samyk/slipstream