Jorge Martinez de Salinas

Opera has introduced a new feature called Opera Unite in its browser. Opera Unite allows service sharing from the web browser. These services include File Sharing, Fridge, Media Player, Photo Sharing, The Lounge and Web Server.

Since it looked promising, I decided to try it out. Setting up the File Sharing service just took a few minutes and everything worked fine. Which made me think … how does it really work? I’m behind a NAT connection and haven’t configured my router which, by the way, doesn’t support UPnP. Perhaps magic? … don’t think so.

To test how it worked I started a file download and fired up Wireshark to examine the packets. They were coming from an Opera server. This happened on the client’s side. On the server’s side Opera had opened a connection to another Opera’s server. So it seems that the service works the same way as a Reverse SSH Tunnel:

1. The browser establishes a connection to an Opera server (tunnel A).
2. When the clients access the service they’re really establishing a connection to an Opera Server (tunnel B).
3. Tunnel A and Tunnel B get connected and the data flows.

The question that comes up is … Does the service always operate this way? Is the connection direct when the user is not behind a NAT or supports automatic port forwarding?

In general the service looks good to me, being its main advantage the ease of use. On the other hand, the information exchange is not strictly between the server and the client (shared files go through the Opera’s network), which can be a deterrent for some users.

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