webRTC - connecting 2 clients on same network

Question

I made a browser chat which sends the offer and answer of the "RTCPeerConnection" by a web-socket server which closes after the transmition (it works).

I would like to make an app which connects only when the 2 clients are on the same localhost/router (no server) and would like to know if it is possible to do any of the next actions:

1. set default port for ICEcandidate (to be able to easily search for the port).
2. make a broadcast to all the possible ports with the offer so i could find the next client.
3. make some static connection with webRTC with predifined settings.

If i gave too much of a broad description please tell.

Thanks.