Question

Is it possible to create a website that makes possible this scenario:

User A logs into the website, uploads a file making a direct TCP connection to user B that it is within the same site at same time downloading the file. Without passing the file trough the server.

How to make user B to listen through a browser?

Would this violate “Same origin policy”?

Point is to use browser and no other software like P2P clients.

Is this crazy idea possible?

Answer 1

I doubt webRTC covers exactly what you need.

You have two issues:

• B, if running from a web browser, cannot open a port to receive an inbound connection
• Even if B were able to do that, you will likely have to face NAT traversal issues.

The solution is to use/implement a relay server:

1. A opens an outbound HTTP/Websocket connection to the relay server
2. B opens an outbound HTTP/Websocket connection to the relay server
3. A sends data to the relay server on the outbound channel (HTTP POST for instance)
4. B reads data from the relay server on the response (to an HTTP GET for instance)

Easier said than done…. (and yes it is a feature of advanced P2P networks like JXTA, XMPP, Skype…, and yes you unfortunately need an intermediate server)

Check ICE for a specification of ‘how to do NAT traversal’