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szimek / sharedrop

Easy P2P file transfer powered by WebRTC - inspired by Apple AirDrop
https://www.sharedrop.io
MIT License
9.94k stars 725 forks source link

It was not possible to establish direct connection with the other peer #87

Open zhouchaoyuan opened 4 years ago

zhouchaoyuan commented 4 years ago

image

valoricDe commented 4 years ago

Which steps did you take to get the other pc shown?

heyakyra commented 4 years ago

Same here, just created a room, shared the link.

valoricDe commented 4 years ago

I could reproduce when my Android is connected with mobile data. Most mobile operators have their connected phones behind a NAT which could be the reason that a direct connection is not possible. If you connect your phone to a Café /any WLAN it should work

heyakyra commented 4 years ago

Doesn't that mean the app does not work as described? I didn't see anything noting that on the website, it only says you can create a room to share with users on other networks

valoricDe commented 4 years ago

I was curious (I'm no maintainer by the way) and read a bit more about and it could be that the mobile provider does not support websocket connections but then the app should fall back to long lived http requests. Don't know if the app does that. I could also be that a so called TURN server is needed to get around this problem. shrug

szimek commented 4 years ago

The way WebRTC works is that in some cases (e.g. if both peers are behind a NAT) it might be not possible to create peer-to-peer connection. WebRTC has a way around it, but it requires using a relay server called TURN (Traversal Using Relay NAT) and, if available, all traffic (still encrypted) goes through this external relay server.

The problem is that TURN servers cost money and this app doesn't bring any. Right now it's really cheap to run it, as the only cost is basically the domain and occasionally a few $ for Firebase.

Maybe I'll add a link in this error message that provides more info.

valoricDe commented 4 years ago

Maybe we can add an open turn server? https://gist.github.com/sagivo/3a4b2f2c7ac6e1b5267c2f1f59ac6c6b

szimek commented 4 years ago

I really would prefer not to use someone else's "open" TURN servers - first of all there's no way for me to check if they are actually ok with it, I have no certainty that these servers don't do something fishy with the relayed data and they could turn them off at any time.

valoricDe commented 4 years ago

I would guess that the owner is probably aware that his relay is used by others but yes that's an argument. The server can not do something fishy as the data is encrypted, or? And if they turn it off it will not work as it does right now too. So nothing lost. On the other hand who want's to send a big amount of data over mobile data anyway. Wifi should be prefered

tejasvi commented 3 years ago

Alas.

sebbes333 commented 2 years ago

The way WebRTC works is that in some cases (e.g. if both peers are behind a NAT) it might be not possible to create peer-to-peer connection. WebRTC has a way around it, but it requires using a relay server called TURN (Traversal Using Relay NAT) and, if available, all traffic (still encrypted) goes through this external relay server.

About the NAT problem. There are a technique called "NAT Punchthrough" or "Nat Hole Punching", I don't know the exact details, I have just read about it some day ago, but I found this: Tool: https://github.com/samyk/pwnat Wiki article: https://en.wikipedia.org/wiki/Holepunching(networking)