Network discovery and establishing connections within Eduroam, a network split in subnets

Question

For our current project we are supposed to create a peer2peer (no server) game application which is played by a teacher and his students on the Eduroam network. The concerns of the stakeholder indicate that he doesn't want server maintenance (so usages of any kind of server services are prohibited) or to perform 'difficult' set up actions (configuring the network).

There are many ways to set up a peer2peer connection within the same LAN, however, on Eduroam everything becomes a bit more difficult. Eventhough the students are connected on the same accespoint, it is not possible to find or contact another student, due to the subnetting behavior of the network. Student A is on a different subnet than student B.

Is it possible in any way, without usage of a remote server or network configuration, for Student A to create a connection with Student B?

(Another offtopic challenge for this project is to create a connection with someone behind a different private network, without usage of a third party or doing network configuration. We have done extensive research for this, but our conclusion is that you either need a server (e.g. hole punching) or you need to configure the network (create a vpn, portforwarding etc.) If you're able to challenge this conclusion, we would glady have your input on this.)

Answer 1

There are two possible approaches to peers finding each other in the network:

1. Broadcasting or multicasting: generally only works within a local subnet/L2 segment unless special forwarding services are provided - won't work.

2. Using a mediator: each peer registers with some service (a directory, DNS server or similar) and they look each other up - this is pretty much ruled out by "no server".

Since eduroam uses a (tunneled) 802.1X scheme to link each user to his respective home network, there isn't much room to do what you're asking. As I understand it, you can't even communicate from one home network to another (at least not necessarily) - this pretty much rules out peer-to-peer in any form.

As you can't change the network (requirement for 1.), your only feasible solution would be a server that's commonly accessible for all clients and that ties sessions together.